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Lignatec Climate-friendly and energy-efficient construction with wood Basic information and implementation

Solar power

O2 CO2

Recycling Heating station

Raw material 50 % C

Particle-/fibreboard factory Construction with wood

ETH / IBI  Novatlantis

Lignum

Sawmill


2  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

This publication has been supported by the following partners:

Contents – Basic information Page 4 5 6

Lignum Cleantech Switzerland Ingenious Switzerland

Abstract: CO2- and energy-efficient timber construction

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1

Conceptual sponsors Baugenossenschaft Zurlinden, Zurich eco-bau / Amt für Hochbauten, Zurich ETH Zurich, IBI Institut für Bau- und Infrastrukturmanagement, Zurich FRM Fédération suisse romande des entreprises de menuiserie, ébénisterie et charpenterie, Le Mont-sur-Lausanne Minergie, Bern Novatlantis / 2000-Watt-Gesellschaft, Villigen PSI Osec, Zurich Swiss Business Hub United Kingdom, GB-London

Partners Flumroc AG, Flums HEV Hauseigentümerverband Schweiz, Zurich Just Swiss Timber Construction Ltd., GB-London Knauf AG, Reinach SVW Schweizerischer Verband für Wohnungswesen, Zurich

Project partners Glas Trösch AG, Bützberg Gutex Holzfaserplattenwerk, DE-Waldshut-Tiengen isofloc AG, Bütschwil Nägeli AG, Appenzellerholz, Gais

Significant financial support BAFU Bundesamt für Umwelt, Bern Holzbau Schweiz, Zurich SHF Selbsthilfefonds der Schweizer Wald- und Holzwirtschaft, Solothurn VGQ Schweizerischer Verband für geprüfte Qualitätshäuser, Biel

9

2 Forests, wood and CO2 2.1 A proactive climate policy for Switzerland 2.2 Possible contributions to climate policy through forest management and wood use 2.3 Potential economic impact of CO2 effects 2.4 Incentive systems to promote greater use of wood products

14 3 Life Cycle Assessment (LCA) Figures – the basis for ecological comparisons 3.1 Introduction 3.2 Methodological basics: LCAs 3.3 Ecoinvent: the basis of all life cycle data 3.4 LCA figures in practice 3.4.1 KBOB recommendation 2009 / 1 ‹LCA data in the construction industry› 3.4.2 ‹Electronic Building Component Catalogue› 3.4.3 Eco-devis and ECO-BKP 3.4.4 Environmental declarations of products and building certifications 3.5 What is behind the indicators used? 3.5.1 Embodied energy according to the SIA 2032 booklet ‹Embodied energy of buildings› 3.5.2 Total primary energy 3.5.3 Global Warming Potential (GWP) or carbon footprint 3.5.4 Environmental Impact Points (UBP 2006) 3.5.5 Other methods and outlook 3.6 Wood in LCAs 19

4 The construction and operation of energy efficient buildings 4.1 Consideration of the models 4.1.1 In the jungle of building labels: what is required? 4.1.2 Energy-efficient buildings 4.1.3 The statutory minimum adjusted 4.1.4 Also relevant for building ecology 4.1.5 Comprehensive sustainability assessment 4.2  Contemporary and sustainable heat generation and intelligent building technology 4.2.1 Wood energy in general 4.2.2 Firewood 4.2.3 Woodchips 4.2.4 Pellets 4.2.5 Tailor-made solutions thanks to sophisticated technology 4.2.6 Solar and wood heating combined 4.2.7 Emissions 4.2.8 The Swiss Clean Air Act (LRV) and energy policy objectives 4.3 Building construction from the perspectives of energy, ecology and comfort 4.3.1 Reference property Hegianwandweg 4.3.1.1 Evaluation of the thermal building envelope according to the standard SIA 380/1 ‹Thermal energy in buildings› 4.3.1.2 Construction methods investigated 4.3.2 Dynamic simulation of thermal properties 4.3.2.1 Model according to the standard SIA 380/1 ‹Thermal energy in buildings› calculates on the safe side 4.3.2.2 Advantageous construction methods depending on the heating demand 4.3.2.3 Comfort in summer dependent on the construction method 4.3.3 Environmental impacts of construction methods and energy standards 4.3.3.1 Methodology for considering the ecology 4.3.3.2 Construction energy: embodied energy and greenhouse gas emissions 4.3.4 Total energy perspective 4.4 Perspective of an investor with a long-term investment horizon 4.4.1 Timber construction with expected returns of investment 4.4.2 Ecological investment motives 4.4.3 Apartment buildings: a growing trend 4.4.4 Optimisation potential

47 5

Outlook


3 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Authors Christoph Aeschbacher, dipl. Forsting. ETH, Zurich Olin Bartlomé, dipl. Holzing. FH, Zurich Regula Gehrig, Communication CO2-Bank, Biel Peter Hofer, dipl. Forsting. ETH, lic. rer. pol., Zurich Paul Knüsel, dipl. sc. nat. ETH, Journalist BR, Zurich Urs Christian Luginbühl, dipl. Holzing. HTL, Biel Katrin Pfäffli, dipl. Arch. ETH / SIA, Zurich Iwan Plüss, dipl. HLK-Ing. FH, Luzern Hansruedi Preisig, dipl. Arch. SIA, Zurich Marco Ragonesi, dipl. Arch. HTL, Luzern Frank Werner, Dr. sc. techn. ETH, Zurich

Specialist support Heinrich Gugerli, Dr. dipl. Ing. ETH / SIA, Zurich

Title information The timber product cycle Manuela Murschetz, Zurich

Contents – Implementation Page 48 6 The environment is an issue – with good reason 6.1 Forests and wood as pioneers of a more sustainable building stock 6.2 CO2-Bank: communication tool for the environmental performance of wood 6.3 Assessment of sustainability 50

7 Background and concept of climate-friendly buildings 7.1 The 2000-watt society as a goal 7.2 Energy and greenhouse gas emissions 7.2.1 Embodied energy / non-renewable primary energy 7.2.2 Amortisation 7.2.3 Target values 7.3 The three areas of operation, construction and mobility 7.3.1 Important factors in operation 7.3.2 Important factors in construction 7.3.3 Influence of the building location 7.4 Special features of the planning process 7.5 The term ‹sustainability› 7.6 The SIA booklet 2040 ‹SIA path to energy efficiency› in context

55 8

Implementation of climate-friendly buildings in accordance with the SIA booklet 2040 ‹SIA path to energy efficiency› 8.1 The Grünmatt estate – timber construction makes it possible 8.1.1 Construction, operation and mobility 8.1.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› 8.1.3 Excursus: ceilings 8.2 Multiple-family house Segantinistrasse, Zurich – conversion beats new construction 8.2.1 Construction, operation and mobility 8.2.2 Overall assessment according to SIA booklet 2040 ‹SIA path to energy efficiency› 8.2.3 Excursus: redevelopment as opposed to new construction 8.3 Hughaus – a clever energy concept 8.3.1 Construction, operation and mobility 8.3.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› 8.3.3 Excursus: energy sources Eichmatt school – one big building instead of two small ones 8.4 8.4.1 Construction, operation and mobility 8.4.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› 8.4.3 Excursus: façades 86

9 9.1 9.2 9.3 9.4 9.5 9.6

Implementation of energy generation and smart building services Primary energy demand and greenhouse gas emissions Wood heating: a broad range of applications Biomass: energy in the high temperature range Wood-fired heating under contract Renewable energy in networked systems Polyvalent supply concepts

91 10 Energy figures as measures of energy reduction 10.1 Transmission heat losses of buildings 10.2 The energy performance certificate based on the SIA booklet 2031 ‹Energy certification for buildings›

95 11

Outlook


4  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Lignum

Holzbulletin 100/2011 Ein Panorama Aufstockung Avenue de Cour, Lausanne Wohnüberbauung Goldschlägi, Schlieren Wohnsiedlung SunnyWatt, Watt Hörsaalgebäude Weichenbauhalle, von Roll-Areal, Bern Neubau Schulhaus mit Turnhalle St. Martinsgrund, Sursee Doppelturnhalle, Borex-Crassier Geschäfts- und Lagergebäude Küchler AG, Schlieren Hotel City Garden, Zug Neue Monte-Rosa-Hütte SAC, Zermatt ‹Rifugio›, Frasco Neubau Tamina-Therme, Bad Ragaz

Die Träger mit den filigranen Holzgittern überspannen in der Doppelturnhalle Borex Crassier 32 m und lassen beim Lichtdurchgang eine ganz besondere Stimmung entstehen. Architektur: Graeme Mann und Patricia Capua Mann, architectes EPFL FAS SIA, Lausanne

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Die technischen Holzinformationen der Lignum

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Sägewerk

Lignum is the umbrella organisation of the Swiss forestry and timber industry and coordinates the cooperation of the Swiss trade associations in this field. Its aim is to achieve sustainable competitiveness and to ensure that thinking and acting are based on common strategies and goals. Through interdisciplinary networking Lignum creates excellence in development and value creation. It expertly represents the interests of the timber industry and is responsible for:  planners, investors, companies  media and the public  research and educational institutions  business organisations  politics and authorities Lignum provides information An essential basis for high quality implementation of ideas is specialised planning, technical and business knowledge. A broad spectrum of well-founded knowledge is taught at vocational schools, technical courses, colleges and universities. Research and development lead to new and promising results, products and processes in the areas of timber systems engineering, materials technology, wood preservation, heat and sound insulation, fire protection, etc. Lignum bundles these cutting-edge findings and passes them on in a practically usable form.

Lignum 29.8.2011 9:31:57 Uhr

The ‹Lignatec›, a double issue of which you are now reading, appears periodically.

Lignum motivates Wood is a material that constantly inspires creative new solutions. Innovations, which otherwise often provoke hostility, meet hardly any resistance when they are made of wood. This phenomenon is certainly based on a long tradition, but also on the positive properties of the material, which is natural, warm and pleasant to touch. Lignum puts wood and wood products in the right light: at trade fairs and exhibitions, specialised courses for planners and businesspeople, in the press, radio, television and the Internet and through its own publications, which appear regularly and are distributed free of charge to members. Lignum raises awareness A great deal of life quality is connected with wood. Forests dominate much of our landscape. They are a place of rest, an important and positive part of our environment. In Swiss forests much more wood grows back than is used, enabling durable, high-quality products to be manufactured. But the successful use of wood requires specialist knowledge. Up-to-date and reliable expert information is required. Lignum provides neutral, clear, expert and practically oriented details about research, production and processing of timber and timber-based materials. You can obtain the information and advice you need directly on the phone or in writing.

Lignum publishes Lignum’s ‹Wood bulletin› is published quarterly. Each issue concentrates on a particular topic and presents innovative ways of building with wood. The ‹Lignatec›, a double issue of which you are now reading, appears periodically. Each ‹Lignatec› issue deals comprehensively with current technical aspects of timber, timber products and processes. The Lignum newsletter provides quarterly information for its members and the industry. Lignum continually provides up-to-date information on all areas of activity to the media and publishes an online journal about wood in Switzerland, updated daily. Lignum’s members have an information advantage Around 4 500 members of Lignum have for years appreciated the benefits of comprehensive, regular and reliable information on wood. They all enjoy substantial discounts on publications and events, a free subscription to the construction information in the ‹Wood Bulletin› and the Lignum newsletter Lignum Journal, as well as regular delivery of the technical information provided by the ‹Lignatec› series. In addition, Lignum offers its corporate members the opportunity to appear on the www.lignum.ch website, which attracts approximately 20 000 visits per month. Other services  Support for the implementation of public and private buildings made of wood  Advice on properties for builders, architects and planners  Expert reports and assessments  Project consulting, expert reports and assessments will be charged on a time and materials basis, or by quotation.  Provision of company addresses

LIGNUM Holzwirtschaft Schweiz Mühlebachstrasse 8, 8008 Zurich Tel. +41 (0) 44 267 47 77, Fax +41 (0) 44 267 47 87 info@lignum.ch www.lignum.ch


5 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Cleantech Switzerland

Helvetic Energy’s success story: partnership in the solar business

Intep’s success story: the 2000-watt society in Vancouver, Canada

Swiss solutions powering a cleaner world Switzerland can profile itself particularly credibly as a clean-tech nation – more than almost any other country. The greatest difference to most other countries is that cleantech in Switzerland not only consists of the efforts of some environmental technology companies, but is really lived by the entire nation. Waste collection, Minergie standards, 97 % of houses connected to sewage treatment plants, energy recovery for all waste and so on: the entire population acts in environmentally friendly ways. Legislation and regulations at the highest levels have driven industrial solutions and led to years of valuable experience. This brings a constant flow of new and innovative developments. Cleantech as an economic factor in Switzerland Cleantech encompasses technologies, processes, goods and services which aim to reduce ecological damage and to enable sustainable use of natural resources and systems. Cleantech is used in all sectors of the economy and affects the entire value chain. It includes the following areas: Waste treatment and recycling Exhaust gas and waste processing Remediation of contaminated sites and soil preparation Consulting, planning and engineering services Efficient energy systems and applications Power generation and recovery Municipal technology Measurement, control and regulation technology Mobility Protection from natural hazards and emissions Water and wastewater treatment As a leading international centre of innovation for highly specialized products and knowledge-intensive services, Switzerland has excellent opportunities to develop and market cleantech products and services for global markets. Our country profits from its image as an environmentally friendly, nature-loving nation which has made environmental protection part of its daily life and has implemented the necessary processes and laws. Due to stringent standards, products approved for the Swiss domestic market stand a good chance of being authorised for export markets as well. However, Switzerland will not become a mere production facility for the mass production of cleantech applications; instead, it is characterised by a heterogeneous business landscape, ranging from start-ups / spinoffs to large multinational corporations.

Cleantech Switzerland – the official Swiss export platform Cleantech Switzerland is the official export platform for the Swiss cleantech sector and was developed on behalf of the Swiss Federal Government. Cleantech Switzerland provides small and medium-sized Swiss companies in the cleantech sector with information, services and contacts, and makes it easier for them to enter the relevant cleantech markets worldwide. The partners of Cleantech Switzerland abroad Via the official Swiss foreign network (over 150 branch offices), Cleantech Switzerland offers a worldwide network for the promotion of Swiss cleantech products and services. In North America (Vancouver) and China (Beijing), Cleantech Switzerland maintains offices to represent you personally. The services of Cleantech Switzerland Cleantech Switzerland supports Swiss cleantech companies in project acquisition and carries out targeted marketing for Swiss companies abroad. In addition, Cleantech Switzerland has a large number of individually designed service packages on offer. As a hub with a database of some 300 cleantech companies, Cleantech Switzerland provides reliable access to Swiss technologies for business partners and project developers abroad. First export successes thanks to Cleantech Switzerland Cleantech Switzerland commenced operations on 1 July 2010. Fourteen organizations are members of the association and over 300 companies have registered on the platform as participants. So far, export business to the value of around CHF 2 million has been initiated and a further CHF 2 million in added value has been activated by the arrangement of new sourcing options. Through additional identification of around 120 projects and 40 partners, important preconditions have been created for further export successes.

cleantech switzerland Herrenacker 15, CH ‒ 8200 Schaffhausen Tel.: +41 (0) 52 560 06 22 Fax: +41 (0) 52 674 06 09 info@cleantech-switzerland.com www.cleantech-switzerland.com


6  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Ingenious Switzerland

Swiss quality craftsmanship in architecture / engineering / design – five good arguments for its use:  Intelligence: Intelligence in the Swiss working culture can ensure the overall success of projects by leveraging a broad variety of know-how. The work of our architects, engineers and designers reflects this – both programmatically and pragmatically. Efficiency: measured efficiency, taking into account the environment and different lifestyles, the local context and the cost effectiveness of projects, forms the basis for successful and stable partnerships.  Courage: converting the unknown into visible form, rising to complex challenges, and travelling new and unusual paths all require courage and independence – qualities that Swiss architects, engineers and designers possess in abundance.  Respect: respect for the people involved in and affected by a project; respect in dealing with technologies and processed materials; respect in the face of the future and a healthy environment.  Experience: pioneering achievements and extraordinary capability are built on experience – and both are well illustrated by typical Swiss products and projects in the fields of architecture, engineering and design. ingenious switzerland – your bridge to the world! The association ingenious switzerland supports its members – Swiss SMEs in the sectors of architecture, engineering and design – in entering new foreign markets. Swiss architecture and design enjoy a worldwide reputation, but the road to foreign success is lined with obstacles and uncertainties: the strong Swiss franc, often difficult economic conditions in foreign markets and complex barriers to trade. ingenious switzerland offers its services in this area and opens new perspectives to its members, particularly SMEs.

Image – the facilitator of added value abroad To ensure the operation and visibility of the ingenious switzerland export platform in target markets, participation in trade fairs is organized involving representatives of our members. Through exhibitions of current judged competitions throughout Switzerland in the fields of architecture, engineering and design, the high performance capacity of the Swiss planning industry is clearly demonstrated. The resulting higher visibility of the members of the ingenious switzerland network increases their rate of success at the international level. Matching – creation of partnerships ingenious switzerland creates a trustworthy and sustainable environment for its members, in order to successfully connect potential buyers with providers. Initial matching possibilities are set up in the ‹ingeniousintimate› format: carefully selected events are organised in the target country with the support of other official agencies in Switzerland to create high visibility at exhibitions, presentations or trade fairs. Potential clients are invited from the target countries to Switzerland to see Swiss know-how and reference projects first-hand, with press accompaniment, and to inform our members directly about their upcoming investment projects. Support – assistance in overcoming export obstacles To help members overcome the numerous major and minor administrative and legal barriers in the target export markets, ingenious switzerland additionally offers SMEs value-adding direct support. Topics include administrative, intellectual property, competition law, insurance and tax-related questions.


7 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Target markets Initial target markets are Germany, France and Singapore, due to their accessibility and high sales potential. There are few language and cultural barriers in dealing with our neighbouring countries. Singapore, with its dynamic development in the fields of architecture and design, is the ideal gateway to the Asian markets. There is an increasing focus on opportunity markets which are already being processed by ingenious switzerland members. ingenious switzerland is employing the ‹blueocean-strategy› in niche markets that have as yet little to no competition, instead of participating in saturated markets at relatively hopeless prices and with cutthroat competition. An example of this strategy is the market entry of ingenious switzerland in Mongolia. As of February 2012 the ingenious switzerland association has about 100 members from the fields of architecture, engineering and design. They are offered the following broad range of services: Inclusion in ingenious switzerland’s database of companies  The opportunity to participate in international fairs Invitations to matchmaking events at home and abroad  Reductions at Osec’s export events  The opportunity to display their logo at ingenious switzerland’s appearances  Specific support for members’ export promotion projects  The opportunity to participate in roundtables and internal exchanges of experience  Receipt of ingenious switzerland’s newsletter with current information on export promotion  Active influence in the affairs of the association

Export successes of ingenious switzerland Seven interdisciplinary member firms formed a cluster for ingenious switzerland’s presence at the Barilga construction fair in Mongolia. At the fair the previously developed case study ‹Mongolian Circus Tower – Towards Zero Emission Architecture› (project development, financing, architecture and urban development, civil engineering, energy and building technology and hospitality consulting & operations) were presented. Based on these activities cooperation agreements were concluded between Mongolian architects and engineering organizations and the Swiss Engineers’ and Architects’ Association SIA; the seven members of ingenious switzerland brought an impressive range of inquiries and orders back to Switzerland. Successful matching also resulted from participation in the Marché International des Professionnels de l’immobilier MIPIM 2011. A member of ingenious switzerland won the opportunity to build a senior citizens’ residence, thanks to the association's presence at the fair.

ingenious switzerland c/o Schweizerischer Ingenieurund Architektenverein SIA Selnaustrasse 16, Postfach, CH-8027 Zürich Tel: +41 (0) 44 283 15 36 www.ingenious-switzerland.com


8  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

1

Abstract: CO2– and energy-efficient timber construction

Global warming is one of the most pressing global challenges. The current emissions of greenhouse gases, particularly CO2, are incompatible with the objectives of sustainable development worldwide. Like many other countries, Switzerland also needs to realign its supplies of resources and energy. Architecture, construction and building technology have a central role to play in this endeavour and the importance of sustainably produced raw materials and energy sources has been increasing correspondingly. The focus is now no longer only on minimizing operating energy, as more comprehensive considerations of the environmental impact of buildings are coming to the fore. Only by considering the whole life cycle of a building can we achieve architecture that is ecologically, economically and functionally sustainable in the long term. Building with wood is advantageous for the environment and beyond There are many reasons to choose wood as a building material. As is generally known, wood is a dry construction material from the start, requires short construction times and has a low dead weight. In addition, wood products generally have a more favourable environmental profile than comparable products made from other materials. This is especially true for the criteria ‹total energy expenditure›, embodied energy and greenhouse gas potential. The results of the study carried out within the framework of this publication add other powerful arguments to the following nonexhaustive list: The study shows that the heating demand calculated from a dynamic simulation is lowest in timber frame construction, but also that the heat storage capacity of this type of construction must be taken into account, according to the Swiss building standard SIA 380/1 ‹Thermal energy in buildings›, which counts against it: to achieve the same heating demand according to the standard SIA 380/1, light construction is incorrectly required to have better U-values than those of solid construction. The standard SIA 380/1 ‹Thermal energy in buildings› therefore discriminates against light construction in favour of solid timber construction and solid construction.  In the accompanying comparison of embodied energy and greenhouse gas emissions from different construction methods the same trend is shown: timber frame construction achieves the best results, followed by solid timber construction and solid construction. Regarding embodied energy, the additional impacts caused by solid construction are around 5 % higher than those of light construction; regarding greenhouse gas emissions they are around 16 % higher. Although the percentage differences may not appear particularly significant, they

may nevertheless be crucial for the achievement of target values. Especially for greenhouse gas emissions, the annual budget is small: for new buildings in the ‹residential› category 16.5 kg/m2 are allowed for construction, total operation and site-dependent mobility, according to the SIA booklet 2042 ‹SIA path to energy efficiency›. Construction usually accounts for more than half this allowance. Around 8 kg/m2 per year remain for operation and mobility. One kilogram of greenhouse gas emissions saved during construction may therefore decisively facilitate the achievement of objectives, when energy requirements are considered holistically. Studies show that buildings must be planned, built and evaluated to ensure optimisation of energy resources. In operation, the decoupling of energy consumption from energy source emissions does not necessarily mean that energy must be saved at any price, but that emissions from a buildingʼs energy supply and construction should be avoided through use of renewable energy sources or construction materials such as wood. In this way, truly CO2-efficient solutions can be achieved in parallel with the most efficient economisation of embodied energy. The new standards Minergie-A and Minergie Eco 2011 seem to setting a promising trend, whereby the seemingly infinite ‹packaging› of the building envelope is replaced by a comprehensive environmental and economic assessment. The maximum summer temperatures correspond to the requirements of the current standards in all types of construction at all times, without additional measures. Compared to solid structures, wood-frame and solid wood buildings require minor allowances. However, the performance of these construction methods can be improved in summer to such an extent that the maximum temperatures are even slightly lower than those of heavy construction, by using the floor heating as a cooling surface in combination with a heat pump.


9 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

2

Forests, wood and CO2

2.1 A proactive climate policy for Switzerland Global warming is now widely recognized as a problem. By signing and ratifying the Kyoto Protocol in 2003, Switzerland declared its support for an active climate policy. Under this agreement it committed to reduce the 1990 level of greenhouse gas emissions by 8 % between 2008 and 2012. Since 85 % of greenhouse gas emissions in Switzerland consist of carbon dioxide (CO2) – with methane (CH4) accounting for just over 7 %, nitrous oxide (N2O) 6 % and synthetic greenhouse gases 2 % – a successful climate policy requires first and foremost a reduction in the burning of fossil fuels. In the CO2 Act of 1999, therefore, a reduction in CO2 emissions of 10 % was stipulated, with a reduction in fuels for household and industry of 15 % and in fuels for transportation of 8 %. Approximately two thirds of Switzerlandʼs current energy needs are still met by oil, gas and coal. The nation-wide emissions of greenhouse gases in 2008 – expressed in so-called CO2 equivalents – were approximately 57 million tons. The primary cause for concern

is the constantly increasing consumption of fuels for transportation. While in 2008 the CO2 emissions from fuels for industry and household were 89 % of the 1990 levels, fuel use for transportation accounted for 114 %. Overall, therefore, Switzerland is far from meeting the requirements of the CO2 Act and from fulfilling the Kyoto Protocol. In response, the Federal Government introduced a CO2 tax on fossil fuels, effective from 1.1.2008. In view of the advance of global warming the Federal Council and Federal Parliament are aiming, by means of the pending revision of the CO2 Act, to reduce greenhouse gas emissions to 20 % below 1990 levels by 2020. For this purpose, measures are planned in buildings, as well as a CO2 tax on fuels for household and industry and fuels for transportation, and participation in the European emissions trading system.

2.2 Possible contributions to climate policy through forest management and wood use

6 CO2 +

C6 H12 O6 +

12 H2O

6 O2 + 6 H2O

9500 MJ solar energy

1 m3 wood = 9500 MJ

0.9 t CO2

stored solar energy (absolutely dry)

0.5 t water

0.7 t oxygen

Nutrients: N, P, K, Mg, Ca

0.3 t water

Figure 1: Photosynthesis and carbon storage in wood. From lowenergy anorganic materials, mainly CO2 and water, energy-rich organic compounds are formed during photosynthesis. 1 m3 of wood chemically binds almost a ton of CO2 as carbon and consists in the absolutely dry stage of about 250 kg carbon, 215 kg oxygen, 30 kg hydrogen and 5 kg other elements.

The forest and timber industry is in a position to contribute to the reduction of CO2 emissions. This has been shown by a study commissioned by the Federal Office for the Environment and published in 2007. 1 Several effects can be distinguished:  The tree converts carbon dioxide from the atmosphere into sugar and oxygen through photosynthesis. The sugar is stored as wood substance in the trunk, branches and bark, while the oxygen is released into the atmosphere. The carbon remains bound in the wood until the tree dies and decomposes in the natural environment or until its timber is burned. Standing trees or even the living and dead biomass in the forest thus form a carbon store. As long as the biomass in the forest increases, we speak of a carbon sink. After the use of the tree or after windthrow, the trunk can be converted into a wood product. The carbon remains stored until the wood product

decomposes at the end of its useful life or until it is burned. If stocks are increased in the technosphere, e. g. through more use of durable wood products, we can also speak of a carbon sink. 2 If a wood product causes fewer greenhouse gases than a competing product from another raw material during its manufacture, use and disposal, a positive substitution effect arises from its use. This more favourable behaviour regarding greenhouse gas emissions is often found in wood products. Products can be considered CO2 neutral when the wood in the course of its growth absorbs as much carbon from the CO2 of the ambient air as it releases during decomposition. From the perspective of climate change, only the additional greenhouse gas emissions resulting from the manufacture of the wood product are therefore relevant. Due to the ease of processing, only a small energy input is usually necessary for this manufacture, which can often be provided by waste wood. However, the use of adhesives, foil, steel connectors, etc., or a shortened life span of the wood product due to inappropriate use, may negatively affect its greenhouse gas profile. The thermal use of energy wood from the forest, as well as wood residues from wood processing and waste wood, create an energy substitution effect. Fossil fuels can be saved in this way.


10  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

In these ways the forest and timber industries can also be put into service to help meet the aims of climate policy. In this connection, the above-cited study notes that: ‹The widest possible deployment of a high level of timber growth in Swiss forests, processing of the harvested wood to durable products in cascade use, and their end use as fuel at the end

Figure 2: Negative numbers refer to CO2 savings. If a Swiss wood product is used in place of a foreign substitute product, CO2 emissions abroad for production, transportation and disposal are not counted.

Figure 3: CO2 effects of individual scenarios in million t CO2 equiv. per year during the period from 2000 to 2100. Negative figures refer to CO2 savings, positive figures to CO2 emissions. Source: Taverna R. et al. 2007

of the product life cycle in the long run lead to the most significant improvement in the CO2 balance›. As a rule of thumb for determining CO2 savings, the following indicators can be assumed:

CO2 emissions saved per quantity of wood used [kg CO2/m3 wood] Switzerland – 300 – 500 – 800

Material substitution Energy substitution Total

In practical terms: in the long run strategies which provide for an increase in use of wood for timber products, especially in construction, are superior to those which put the main emphasis on its use for energy production. The advantage of the use of wood as material as opposed to its direct use for energy is that the savings are twofold: first, in the manufacture of wood products and secondly in energy recovery when the products are used as fuel. In the optimal scenario according to the study (cf. the curve ‹Increment optimised: building› in figure 2) the increase in wood consumption in construction, including furniture, in the years 2000 to 2030 would be 80 %. After that, use is treated as constant, for the purpose of studying the impact

Abroad – 400 – 100 – 500

Global – 700 – 600 – 1300

of the trend. The growth rate of wood consumption was estimated from the current market shares of timber for building components. The greatest potentials were detected in the construction field, especially in storey ceilings and load bearing walls.

Total effects for Switzerland, considering individual scenarios (strategies) 2000

2010

2020

2030

2040

2050

2060

2070

6 4 2 0 – 2 – 4 – 6 – 8 – 10 – 12 – 14

  Increment optimised: building   Increment optimised: energy  Baseline   Reduced forest maintenance

  Kyoto optimised

2080

2090

2100


11 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

When considering CO2 effects via scenarios a distinction should be made between global and domestic effects. The global impact is of the utmost importance for solving the greenhouse problem. However, the Kyoto Protocol uses an accounting system which focuses on individual countries, and therefore it is essential to distinguish which CO2 savings are achieved at home and which abroad. In Switzerland a policy based on the best case scenario ‹Increment optimised: building› could eliminate over 8 million tons of CO2 emissions per year between 2016 and 2026. Compared with 1990, this would achieve additional reductions of around 6.5 million metric tons of CO2 equivalents. Over 11 % of today’s annual greenhouse gas emissions could thus be avoided if the forest and timber industry, and wood consumption, developed in accordance with this scenario. The time frame for this reduction is, however, significantly longer than that of the first Kyoto commitment period.

Figure 4: CO2 effects of the scenario ‹Increment optimised: building› in million t CO2 equiv. per year during the period from 2000 to 2100. In contrast to figure 2 the sum of the effects for the year 2000 was set to zero. Negative figures refer to CO2 savings, positive figures to CO2 emissions. Source: Taverna R. et al. 2007 (Curve ‹Forest sink› adjusted for 2050 to 2070)

While forests will initially continue to function as a carbon sink, despite an increase in todayʼs level of wood use, after about 50 years they will become a source. This is due to the constant increase in use, which means that some residues from wood harvesting will remain in the forest and rot there. The expansion in the use of wood in all areas, particularly in the construction industry, means that wood stocks in the technosphere will increase for over 100 years. After around 120 years, products leaving the building stock and new products entering it will be in approximate balance. The effects of material and energy substitution will then remain at a stable level. Taverna R., Hofer P., Werner F., Kaufmann E., Thürig E. 2007: CO2-Effekte der Schweizer Wald- und Holzwirtschaft. Szenarien zukünftiger Beiträge zum Klimaschutz. Umwelt-Wissen Nr. 0739. Bundesamt für Umwelt, Berne

1 

Calculations and further information can be found e. g. on the website of the CO2-Bank Schweiz (www.co2-bank.ch). The exact climate performance of individual companies can be recorded and viewed here.

2 

Progression over time of the individual annual effects based on the scenario ‹Increment optimised: building› 2000

2010

2020

2030

2040

2050

2060

2070

2080

4 3 2 1 0 – 1 – 2 – 3 – 4 – 5 – 6 – 7

  Material substitution   Forest sink

  Energy substitution   Sum of the effects

  Wood store changes

2090

2100


Climate-friendly and energy-efficient construction 12  with wood – Basic information and implementation

2.3 Potential economic impact of CO2 effects As part of a case study for the canton of Graubünden, the value creation of the forest and timber industry was calculated and the scope of CO2 effects and their value were estimated. 3 The value creation was calculated on the basis of a survey of material flows in the canton.

Figure 5: Source: Walz A., Taverna R., Hofer P. 2009

Gross value creation of the forest and timber industry in the canton of Graubünden in 2007 Industry Gross value creation [CHF millions] Forestry (including federal contributions for forest protection) 57 1st processing stage (sawmills, board factories, wood / cellulose processing plants) 32 Wholesalers (for wood and building elements made of wood) 9.2 15 2nd processing stage (moulding plants, windows and doors, building elements) 264 3rd processing stage (joineries, carpentry companies, kitchen construction, paper manufacture) Total 377

To determine the monetary value of the CO2 effects, the CO2 storage areas were based on inventories of the forests in Graubünden and on a material flow study of the Graubünden timber industry. Furthermore, an environmental evaluation was made of the products used. With the current emission certificate prices of around 18 € / t and a € exchange rate of CHF

Figure 6: Effects of the current wood use in 2007: Wood replaces wood and other materials which are partly produced abroad in equal proportions. Negative figures refer to CO2 savings and potential compensation yields. Source: Walz A., Taverna R., Hofer P. 2009

below shows that the main value creation takes place in the third stage of processing, involving joinery and carpentry companies and the paper industry.

Percentage 15 9 2 4 70 100

1.30, the CO2 effects in the industry were assessed at approximately 23 CHF / t. Considering the significance of each individual effect, the values for compensation were highest for timber stocks in the Graubünden forest (cf. figure 6).

CO2 effects in 2007 and potential value in CO2 trading Savings [1000 t CO2-equiv.] Storage effects in the technosphere Material substitution

Energy substitution

Transport emissions

Forest effects

Total

in Canton Graubünden outside Graubünden Total in Canton Graubünden outside Graubünden Total in Canton Graubünden outside Graubünden Total in Canton Graubünden outside Graubünden Total in Canton Graubünden outside Graubünden Total in Canton Graubünden outside Graubünden Total

– 121 – 46 – 166 – 3.4 – 115 – 118 – 65 – 65 – 130 10 12 22 – 607 – 29 – 636 – 786 – 243 – 1029

Costs of CO2 compensation In millions of CHF – 2.5 – 1.1 – 3.5 – 0.07 – 2.38 – 2.45 – 1.35 – 1.35 – 2.7 0.21 0.25 0.46 – 12.56 – 0.6 – 13.16 – 16.28 – 5.03 – 21.3


13 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

It is worth noting, however, that this is a static analysis. With a policy that aims to increase forest growth and expansion of wood use in the canton, the CO2 effects could be extended considerably. They would move into the storage areas in the technosphere, and the material and energy substitution effects would be significantly greater. The intensified use of wood in the canton of Graubünden would reduce the forestʼs proportion of value creation due to the reduced development of storage areas. However, based on the

2.4

CO2 savings, the amount of compensation payments for the timber industry would remain at modest levels, even with increased wood use, compared to the potential value creation from the expansion of wood use. Walz A., Taverna R., Hofer P. 2009: CO2-Effekt und ökonomische Bewertung von Holznutzung und Senkenleistung im Kanton Graubünden für das Jahr 2007. (CO2-effect and economic evaluation of wood use and the sink effect in the Canton of Graubünden for 2007). Produced on behalf of the Federal Office for the Environment, Davos and Zurich

3 

Incentive systems to promote greater use of wood products

The question is, what incentives can policy provide to steer the economy in this direction? How can it be ensured that more wood products will be used, above all in construction? In the first commitment period, each country was allowed credit for the increase of carbon storage areas in the forest, under Article 3.4 of the Kyoto Protocol. For Switzerland, which chose this option, this represents a maximum of 1.8 million metric tons of CO2 per year. However, in the absence of a policy framework and a financial incentive system, this opportunity is not practically relevant for forest owners in Switzerland today. So far a country has not been allowed credit for wood stocks in the technosphere. This point is being negotiated with regard to the second Kyoto commitment period after 2012. The main question is, who will receive the credit for the increase in timber storage areas and who will carry the burden of their liquidation: will it be the wood-producing or the wood-consuming country? Currently it seems that the major producing countries have the upper hand. Todayʼs CO2 tax on fossil fuels and the sale of CO2 savings, for example in the replacement of fossil fuels by biomass power plants, are creating favourable conditions for wood products. Both instruments make non-fossil energy sources more competitive than fossil fuels. Non-fossil energy sources are cheaper, and products that are made with less fossil energy will become more attractive in future. If more wood products are manufactured in Switzerland in the place of energy-intensive substitutes, or if heat and electricity are increasingly produced with wood, the CO2 balance of the country will improve. Apart from the CO2 tax on fuels, there are still no instruments in force in Switzerland which could steer these positive effects of the forest and timber industry in the right direction at the level of forest owners and manufacturers, namely a comprehensive cascade use of sustainably produced wood. Granting contributions for storage increase in forests is problematic not least because of the complex division of ownership. Moreover, a forest owner who is affected by

a catastrophic windthrow must pay back the money received for building up stocks again. This would apply precisely at the time when he is also struggling with the economic consequences of the disaster. As the study shows, however, in the canton of Graubünden a company could obtain very welcome operating capital by the gradual development of stable sink forests that are not too rich in reserves. Rewarding the building up of timber stores in the technosphere seems possible in principle, but is subject to various methodological difficulties. In this connection, the revised CO2 law introduces new opportunities, as it explicitly stipulates that wood stores should be considered. The wood industry would do well to explore these possibilities. The positive effects of consistent use of forests and timber on the cascade principle – first creating wood in products of the highest possible value and then recovering energy at the end of a productʼs life – are proven. The Federal Government has therefore formulated a wood resource policy and is aiming at the efficient use of resources and elimination of weaknesses with its ‹Swiss Timber Action Plan›. The National Research Programme 66 ‹Resource Wood› was launched in late 2010. It aims to provide an improved foundation for wood use in the future. Apart from the future opportunity to promote wood use directly, concepts for the appropriate and economical use of wood in construction should be encouraged. It is to be hoped that good concepts will be supported by measures on the part of the public authorities to further improve economic efficiency.


14  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

3  Life Cycle Assessment (LCA) Figures – the basis for ecological comparisons 3.1 Introduction The importance of product-related environmental information has increased steadily in the Swiss construction sector in the last ten years. While the focus in the planning of a building used to be on minimising the operating energy – i. e. optimising the energy balance – a more comprehensive view of the environmental impact of buildings is increasingly occupying centre stage, for example through bidding processes or building certificates. The latest trend in this development, particularly at international level, is represented by building evaluation and certification schemes, which often promote not only environmental aspects, but also a comprehensive sustainability assessment of a building over its entire lifetime. Various information booklets and recommendations of the Swiss Society of Engineers and Architects (SIA)

or the Coordination Conference of Federal Construction and Properties Services (KBOB), and the planning tools based on them, methodologically assist planners and decision makers in planning and constructing buildings in environmentally sound ways. They also often provide appropriate parameters for individual building materials and processes. In Section 4.3 below a reference building is simulated, based on these documents and tools, and appropriate calculation programs. But where do these parameters come from, how reliable are they and what must one know to work with them usefully?

3.2 Methodological basics: LCAs When experts talk about ‹Environmental Impact Points UBP›, ‹EI99 points› the ‹GWP IPCC 2007 (100a)› or embodied energy, there is one common theme behind their conversations: Life Cycle Assessments or LCAs. These were created in the late 80 s from the realization that pure energy considerations, or the underlining of individual product properties by a label, have only limited suitability for describing the environmental relevance of products and processes. The now generally accepted basis of life cycle assessment is the ISO 14040ff series of standards. This series establishes the basis for calculating and assessing the environmental impact of products, albeit at a very general level. While this broad approach allows the standards to be widely applied, it also leaves a great deal of room for interpretation in individual cases. LCAs make a basic distinction between the accounting of material flows, such as raw materials, auxiliary materials, waste, process emissions in soil, water and air (keyword: Life Cycle Inventory – LCI) and the evaluation of these material flows – simply put: the evaluation of all emissions into the natural environment of all these material flows in terms of their environmental impact (keyword: impact assessment). The importance of this distinction and the normal evaluation methods used in the construction industry in Switzerland today will be discussed later. Much mischief can be caused by Figures from LCAs, due to the latitude allowed in calculation, but also to uninformed interpretation of the information. When working with LCA Figures, the following points should therefore be kept in mind:

 Comparisons are only useful when related to the same functionality of products: in the case of building products this means their use in a building. Comparisons per kg or per m3 are usually not based on the same functionality and are therefore generally not useful. 4 Consideration of various lifetimes is fundamental in determining the functionality for comparison purposes. Comparisons are meaningful only in consideration of the entire life cycle, taking into account transportation, the use phase and the disposal phase, in order to avoid wrong decisions due to the shifting of environmental burdens into segments not taken into consideration.  Methodological framework conditions 5 that are consistent and appropriate to the context under consideration are a prerequisite for the comparability of LCA data. So much for the methodology, but where do the Figures come from? Even if this is not universally heeded: http: // www.creabeton-materiaux.ch / fileadmin / Downloads / News / Beton_deutsch.pdf

4 

E. g. in the accounting of processes with several products or in the use of recycling material or the recyclability or thermal recovery potential of a product (keyword: ‹allocation›)Verwertbarkeit eines Produktes (Stichwort: ‹Allokation›)

5 


15 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

3.3 Ecoinvent: the basis of all life cycle data Data from the ‹Ecoinvent› 6 database are mostly used when a life cycle assessment is now calculated in Switzerland. This database is now operated as one of the worldʼs leading LCA databases by the Ecoinvent Centre, a consortium of different institutions from the ETH domain. Ecoinvent includes over 4000 LCA datasets on electricity and heat production, transportation, building materials, metals, chemicals, plastics, waste disposal processes, etc. that are created and documented using detailed methodological standards and quality guidelines. These datasets are also the basis for all LCA data shown in the SIA or KBOB datasheets and the tools based on them. It is therefore worthwhile to consider some characteristics of the data from Ecoinvent: 7 Ecoinvent data (and the data derived from them and published) represent average processes and products, e. g. related to Switzerland or Europe. This means that these data can be consistently used for decision support only as long as the conditions for averaging are not changed by the decision (which could possibly happen in very large infrastructure projects): 8 In Ecoinvent datasets no credits are awarded for co-products 9, for the recycling of materials or for energy from the thermal recycling of waste. On the other hand, only the environmental impacts of collecting and processing are calculated when recycled materials are used in manufacturing. 10 From the wood perspective: it is true that the storage of biogenic carbon in wood products is recorded in the inventory, but this is not taken into account when the global warming potential (GWP) is calculated (see below). For databases of this size and complexity there is always one major problem: updating. This problem is

3.4

accentuated by the fact that in recent years technological development and the requirements of environmental protection – not least in response to the CO2 Act – have often produced significant increases in efficiency and reductions in climate impact and environmental burdens. Since the updating of average datasets involves a significant coordination effort (e. g. by an association), such process improvements are seldom recorded in updated records, especially in industries dominated by SMEs. It is all the more welcome, therefore, that the Federal Office for the Environment will be actively involved in updating the datasets on forestry processes and wood products in the next two years. 06 

http: // www.ecoinvent.org/ The Ecoinvent database is currently being completely revised; the information given here is based on Ecoinvent version 2.2.

07 

LCA experts talk of descriptive, ‹average› LCAs in contrast to decision-oriented LCAs with a ‹marginal› approach.

08 

09 

from a process with several products as the output Credits are probably the most controversial method in life cycle assessment. While the datasets in Ecoinvent do not show any credits, the data structure of the database does enable credits to be included in a specific LCA, depending on the application and on the user’s personal values.

10 

LCA Figures in practice

3.4.1  KBOB recommendation 2009/1 ‹LCA data in the construction industry› A significant contribution to the use of LCA data in the construction industry has certainly been made by the KBOB Recommendation 2009/1 ‹LCA data in the construction industry› 11 from the Coordination Conference of Federal Construction and Properties Services (KBOB). In this recommendation LCA Figures for all major construction products and processes, including building services, transportation and energy supply, are compiled on the basis of Ecoinvent (and studies based on it). This list is the basis for various instruments for the environmental assessment of construction products and buildings, which are presented briefly below. First, however, it should be noted that:

 Through the direct transfer of Ecoinvent datasets for building products, the methodological guidelines for the creation of datasets in Ecoinvent will also become the default for life cycle assessment of building products by the public sector in Switzerland.  If LCAs are to be updated not only in the KBOB list or in lists and tools derived from it, but also in the SIA’s information booklets, this must now, practically speaking, be based on the updating of the datasets in Ecoinvent.


16  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

3.4.2 ‹Electronic Building Component Catalogue› The web-based and dynamic ‹Electronic Building Component Catalogue› 12 is the contemporary replacement of the SIA documentation D 0123 ‹Building construction from ecological perspectives›, dating from 1995. The Internet user can choose components, such as cavity wall masonry, from the catalogue and dynamically determine the option required by changing individual materials and layer thicknesses. Via mouse click, U-values and current values for environmental partial evaluations (SIA 2032 booklet ‹Embodied energy of buildings›: embodied energy and greenhouse gas emissions) and an overall assessment (Ecological scarcity: Environmental Impact Points UBP) are calculated and presented in tabular form and graphically. In addition, the building performance can be calculated. These results generated online are available for the user to print in PDF format and electronically via an XML interface for suitably equipped software. The results of the calculations can serve only as rough estimates and guidance in the pre-project or early stages of project planning. Merely looking at the layers of a building component neglects e. g. connectors, fasteners, suspensions, etc., which can significantly determine its environmental profile. More detailed information is necessary to provide a more exact economic analysis of a building. 13 3.4.3 Eco-devis and ECO-BKP Not all planners enjoy grappling with LCA Figures. For this reason, the association Eco-bau has developed the planning tool Eco-devis. 14 Eco-devis identify ecologically interesting performance graphically. They are available as an additional component in the most common costing programs for the standard construction works catalogue of the Swiss Central Office for Building Rationalisation CRB. This enables construction works which cause less environmental impact to be offered for tender without additional effort. The most important information from the eco-devis is listed in the ECO-BKP 15 factsheets. The assessment of products for eco-devis is made partly on the basis of environmental declarations according to the SIA recommendation 493 ‹Declaration of ecological characteristics of building products›. Environmental impacts during manufacture, processing, use and disposal of building materials are assessed. Embodied energy is used as a measure of resource consumption and environmental pollution in the production of a building material. In the processing stage, the amount and type of solvent emissions (VOCs) are in the foreground. During use, the presence and emis-

sion potential of environmental components in the materials, such as problematic flame retardants, etc. are considered in the assessment. Re-usability, environmental effects of incineration and landfill type are the assessment criteria for the disposal of the products. 3.4.4  Environmental declarations of products and building certifications LCA Figures have also reached the world of labels and environmental declarations. The above-mentioned SIA recommendation 493 ‹Declaration of the ecological characteristics of building products› enables companies to give LCA information on their products, among other details, in a self-declaration. In addition, the embodied energy of building materials as defined in SIA booklet 2032 ‹Embodied energy of buildings› has found its way into the building labels Minergie-Eco and Minergie-A as a performance characteristic. We can assume that the importance of LCA-based environmental information on products will increase. On the one hand, LCA information on climate impact (Basic Requirement No. 3) and on sustainable resource use (Basic Requirement No. 7) will now be required by the European Construction Products Directive for the new CE mark. On the other hand, the standardization activities of CEN TC 350 will lead to harmonized European rules for the environmental declaration of products and the evaluation of the sustainability of buildings. These developments, in combination with a further development of building certification, will continue in future to increase the need for consistent, up-to-date, representative, and even manufacturer-specific environmental information, based on LCAs. http: // www.bbl.admin.ch / kbob / 00493 / 00495 / index.html

11 

http: // www.bauteilkatalog.ch

12 

A set of standards for this purpose is currently being worked out within the CEN TC 350 responsible for the auditing of buildings for sustain-ability. The practicability of these standards still needs to be proved.

13  

http: // www.eco-bau.ch / index.cfm?ID=16&Nav=15

14  

http: // www.eco-bau.ch / index.cfm?Nav=15&ID=15

15  


17 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

3.5 What is behind the indicators used? In the above-mentioned instruments and also in the examples later in this book various indicators for the environmental impact of building products and buildings are documented. What is behind these indicators, and what is their significance? Embodied energy according to the SIA 2032 3.5.1  booklet ‹Embodied energy of buildings› Embodied energy as defined in the SIA 2032 booklet ‹Embodied energy of buildings› 16 quantifies as ‹nonrenewable primary energy› the cumulative energy consumption of fossil and nuclear fuels and wood from deforestation of primary forests. For each nonrenewable energy source, an extrapolation is made over the entire supply chain of how much crude oil, crude gas, uranium ore, etc., expressed in MJ, must be extracted from the natural environment. How this affects the construction and operation of various buildings can be clearly seen in the data for the example building in Sections 4.3.2 and 4.3.4. 3.5.2 Total primary energy In addition to ‹non-renewable primary energy›, ‹total primary energy› quantifies the cumulative energy cost of renewable energy sources. Renewable energy sources include hydropower, wood / biomass from sustainable sources, solar, wind, geothermal and ambient energy. With this parameter, the amount of energy supplied to the building (final energy) is calculated according to SIA booklet 2031 ‹Energy certificate for buildings› and to SIA booklet 2040 ‹SIA path to energy efficiency›. Occasionally this indicator is also shown for individual materials, e. g. in the 2009/01 KBOB recommendation or in the ‹Electronic Building Component Catalogue›. It should be also emphasised that this indicator is not suitable for the assessment of building materials, as it represents resource extraction and not energy consumption. 17 Since the energy content of wood is considered as resource extraction, this means that wooden structures are usually associated with a significantly higher use of total primary energy than other comparable structures – even though the energy content is available for energy recovery after use. The conclusion from this indicator for wood would be to use wood directly as an energy source instead of employing it repeatedly in cascade use as a building material and energy source. This contradicts the results from studies such as those cited in Section 2.2 on the sustainable use of wood and is in clear contradiction to the resource policy of the federal government, according to which the demand for wood products is increasing and the resource should be used in a cascade and repeatedly. 18

3.5.3  Global Warming Potential (GWP) or carbon footprint Within the climate debate and in terms of ‹carbon footprints›, Global Warming Potential (GWP) has greatly increased in importance in recent years. 19 GWP is an indicator for global warming and quantifies the cumulative global warming effect 20 of various greenhouse gases compared to the effect of a similar mass of CO2. The GWP is therefore expressed in CO2 equivalents. It is one of several possible indicators of climate impacts and its calculation is based on the cumulative radiation absorption capacity of a substance over a specific period, usually 100 years. Although the indicators mentioned above only represent partial aspects of the environmental impact of a product, they can be fairly reliably calculated because they correlate strongly to energy consumption, information on which is normally relatively exact. 3.5.4 Environmental Impact Points (UBP 2006) The methodology of ‹Environmental Impact Points› (UBP 2006) provides a picture, in the evaluation stage, of those environmental impacts which are targets of Swiss environmental policy. The UPB 2006 quantify the environmental impacts of the use of energy resources, land and fresh water, of emissions in air, water and soil, as well as through the use of landfill space. Methodologically, the calculation of the UBP shows the mass and energy flows caused by a material in relation to the maximum flows allowed by Swiss legislation. 21 A comprehensive examination of the environmental impact of products beyond embodied energy and greenhouse gas potential is certainly desirable, but the results of such broad-scale methods are fraught with much greater uncertainties, not least because knowledge about process emissions is generally much more limited, due to lack of measurements, than what is known about energy-related emissions, and because the impact assessment of individual emissions must be based on many simplifications with regard to various environmental problems. 22


18  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

3.5.5 Other methods and outlook A variety of other assessment methods have been developed for impact assessment in LCAs, not least methods which, like Global Warming Potential (GWP), designate and quantify the environmental impact of a product in relation to other potential effects – ‹environmental problems› such as acidification, ‹summer smog›, overfertilisation, etc. An environmental impact assessment based on different potential effects is planned in the proposed European standards for sustainability assessment of buildings in CEN TC 350, for example; such indicators do not currently play a prominent role in the building sector in Switzerland.

The definition of embodied energy in this datasheet differs from that given in the Bundesamt für Umwelt-Schriftenreihe (Federal Office for the Environment publication) Umwelt 307 ‹Ökologische Bewertung mit Hilfe der Grauen Energie›. In the Federal Office for the Environment publication, water energy is included under embodied energy, which leads to considerably higher embodied energy values, if this publication is followed.

16  

17 

This is also valid for plastics regarding embodied energy.

18 

BAFU 2008, Ressourcenpolitik Holz; Strategie, Ziele und Aktionsplan Holz An interesting discussion is currently taking place on the meaningfulness of limiting energy consumption as part of the 2000-watt society, when apart from resource aspects regarding non-renewable energy sources, the most urgent aim from an environmental point of view is limiting CO2 emissions.

19  

This indicator should therefore not be equated with location-bound CO2 emissions, which are the subject of agreements on targets with the federal government as part of the CO2 Act.

20  

For this reason UBP is also described as a ‹method of ecological scarcity›.

21  

In LCA, therefore, the main reference is to potential effects.

22  

3.6 Wood in LCAs How do wood products really compare to other materials in LCAs? When wood products are compared, in conformity with standards, to functionally equivalent products, more than 15 years of life cycle assessment have shown the following 23:  Wood products generally have a more favourable environmental profile than comparable products from other materials. This is especially true for the total energy consumption (excluding energy stored in the timber itself), embodied energy or GWP, but also regarding lower production of substances going to landfills. Naturally, the consumption of renewable energies is higher in the production of wood products than in comparable products, mainly because a large proportion of these energies is stored in the product and can be used at the end of its life.  Preservative-treated products tend to show higher values with regard to toxicological indicators and photochemical smog (depending on the wood preservative used). New generations of metal-free wood preservatives – or also design-based wood protection – seem an appropriate way to reduce these environmental effects.  The burning of wood products can lead to higher values for the indicators acidification or eutrophication than comparable products. However, the energy can be recovered and, through replacement of conventional fuels and electricity, reduce the impact on the environment.  The environmental profile of wood products is not generally dominated by the timber itself. Much more crucial, for example in panel materials with a very high share of residual wood, is the high proportion of adhesive used, in addition to the fuel needed to produce the heat used for drying. In construction

applications the frequently high proportion of steel used for connection technology often leads to a significant rise in the environmental profile’s values for wood products.  The life cycle of wooden houses is mostly dominated by materials that are beyond the scope of wood, such as the basement / foundation, fire and noise protection measures, building services, etc. For example, the values for the embodied energy of timber houses are 10 – 15 % lower than those for solid construction (cf. also Section 4.3.3.2). It has also been found that the results of such comparisons depend strongly on methodological assumptions and implicit attitudes. Here, the timber industry must carefully keep track of efforts to standardise sustainability auditing of construction products and buildings. Not least, the ecological advantages of wood must be communicated to planners and decision makers in the construction sector and be made easily accessible in the planning process. It is hoped that this ‹Lignatec› publication will make a useful contribution in this context. Werner F., Richter K. 2007: Wooden building products in comparative LCA; a literature review. International Journal for Life Cycle Assessment, 12(7): 470 – 479

23  


19 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4

The construction and operation of energy efficient buildings

4.1 Consideration of the models 4.1.1  In the jungle of building labels: what is required? Is timber construction ecological enough to do without labels or certificates? An overview of the assessment systems shows that the requirements of energy-efficient building are increasingly being supplemented by more comprehensive criteria, whereby sustainability is the particular feature which most convincingly highlights the many positive qualities of timber construction. 4.1.2 Energy-efficient buildings The scale for an energy efficient building moves between the mandatory standards, namely the standard SIA 380/1 ‹Thermal energy in buildings› standard, and the voluntary standards Minergie, Minergie-P (similar to the passive house standard) and Minergie-A. One of seven new houses in Switzerland is awarded a Minergie certificate. Since its launch ten years ago, this standard has achieved a market share of around 15 %,

Figure 7: Weighted energy rating for the heat of new buildings in litres of heating oil equivalents per m2 in building standards and statutory regulations

underlining how sought after improved energy efficiency and high comfort levels have become. A growing number of building owners are thus showing their willingness to do more than the law requires in the SIA 380/1 standard, of their own free will. To achieve the Minergie certificate, the thermal insulation in the building envelope must be improved to such an extent that the minimum mandatory standard for buildingspecific heating demand can be reduced by around 20 %. In addition, the Minergie building label also provides a limit value for total energy efficiency. But ambitious energy ratings are not enough: a clearly intended side effect is the creation of comfortable living conditions. In a Minergie house systematic air renewal must be ensured by a mechanical ventilation system.

Weighted energy rating for the heat of new buildings 25

22

20 15

12

9

10 4.2

4.8

3.8 3

5 0

Normal new Model directive building 1992 1975

Model regulations 2000

Minergie 1998

Apart from their technology, Minergie-certified buildings are often associated aesthetically with the simple and modern style of wooden detached houses. This broad perception is in fact justified. The assumption that timber construction usually creates favourable conditions for a home with above-average energyefficiency can be easily confirmed. Both the design qualities and the functional and structural properties of wood as a natural building material support this assumption. This is because in contrast to solid construction, in timber frame construction the bearing and the insulating layers are combined, making the walls thinner. Load-bearing timber is therefore deliberately chosen as a design principle for many buildings with the Minergie-P standard in order to achieve the high energy efficiency levels required. But the higher the requirements, the less it is sufficient to reduce transmission losses only via the building

Model regulations 2008

Minergie 2009

Minergie-P

0 Minergie-A

envelope. New buildings with a heating demand so low that conventional heating can be dispensed with are best geared to a passive solar gain – from both the design and structural points of view. These include firstly the buildingʼs orientation and secondly a compact building form which is characterized by a very low ratio between the area of building envelope surfaces and the volume. Because timber is thought of as light and having low thermal mass, it is often supplemented structurally with elements (ceilings) or a mineral building core. The Minergie P house – with or without wood – is at least three times more energy-efficient than an average twenty year old house.


20  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.1.3 The statutory minimum adjusted The state of the art in building technology has advanced rapidly in the slipstream of innovative building concepts and voluntary standards. The current new building regulations have halved heating demand compared to ten years ago. This leap in efficiency was caused by the model rules of the cantons in the area of energy (MuKEn), which the Conference of Cantonal Energy Directors (EnDK) established as of 2008. These rules reduced the previous 9 litres of fuel oil equivalent (per m2 energy reference area EBF) to 4.8 litres. The implementation of the model rules in the individual cantons has since progressed well: at least as far as the stricter energy certification for new buildings is concerned, nearly all cantonal building and energy legislation has been adapted to conform to the national harmonization proposal of the EnDK. There are still considerable differences between the statutory minimum level and the Minergie standard, however. These are not only based on the improved thermal quality of a certified building envelope. Overall energy efficiency must also be considered for the building label. With the Minergie criterion ‹heat energy› (formerly ‹weighted energy rating›) the energy requirement is additionally limited for hot water, air conditioning and building services auxiliary equipment. Renewable energy sources are the subject of statutory regulations, in that minimal supply ratios of these sources are required for heat production and the heating of buildings. Similarly, the use of these energy sources to meet voluntary building standards is extremely helpful and sometimes even an essential requirement. For this purpose solar thermal systems (solar panels), heat pumps or wood furnaces are the most common methods used. For the label MinergieA, in existence since early 2011, the use of renewables is even made a condition: over the course of the year Minergie-A certified houses must cover their needs sufficiently with self-generated energy. Certified buildings also demonstrate that own energy production is possible with a simultaneously limited proportion of embodied energy.

4.1.4 Also relevant for building ecology Detailed analyses 24 of existing buildings show that in an average building there is considerably less embodied energy – involved in the manufacture and transportation of the materials used - than the operating energy required over the life cycle. In energy efficient buildings, however, the two proportions come perceptibly closer, although the embodied energy of more airtight and better insulated building envelopes can increase slightly (cf. Section 4.3.3.2). As the study described below also shows, it is necessary to account for embodied energy not only in energy efficient buildings but also in the implementation of sustainable building concepts. A consolidated evaluation process for resource-specific and building ecology aspects is included in the Minergie supplement ‹Eco›, for example. This includes recording the embodied energy of all building materials used (according to the SIA booklet 2032 ‹Embodied energy of buildings›). In addition, the focus is also on the flexibility of building materials and their deconstruction, and also on the use of recycled materials and product labels like Natureplus or Blauer Engel. A Minergie-Eco-certified building must also fulfil other health-promoting criteria. For example, the daylight conditions and any imissions caused by noise or ionizing radiation must be specifically evaluated. A low pollution load also promotes a good indoor climate. The non-renewable primary energy factors for the construction sector are listed in SIA booklet 2040 ‹SIA path to energy efficiency›.

24 


21 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.1.5  Comprehensive sustainability assessment The evaluation of buildings designed to meet the requirements of the 2000-watt society places an even greater emphasis on the finite resources required. For this purpose primary energy is particularly emphasised in the auditing of buildings: it represents, as described in Section 3.5, the sum of usable final energy and of all resources used in upstream processing and transport chains. This refers primarily to the provision of building materials, for which reason renewable resources such as wood must receive a positive evaluation. 2000-watt compliant buildings in accordance with the SIA booklet 2040 ‹SIA path to energy efficiency› are required to meet a target value for construction, operation and mobility. Around two dozen new buildings or renovated buildings, including apartment buildings and business premises, have already been planned and constructed accordingly.

Figure 8: Guide values according to SIA booklet 2040 ‹SIA-path to energy efficiency› for the areas of operation, construction and mobility. Source: Amt für Hochbauten, Stadt Zurich (Department for Buildings, City of Zurich)

While building labels like Minergie represent the system ‹house› as a fixed assessment framework, the SIA booklet 2040 ‹SIA path to energy efficiency› is being expanded for the first time to include the building location and gives a quantitative statement about it. Accessibility by public transport or the mobility impact of the individual have been made indicators of a sustainable building, which is correct insofar as mobility stimulates energy wastage as much as the normally inefficient building stock.

Typical primary energy and greenhouse-gas distribution in 2000-watt compatible buildings 100 %

59 %

66 %

19 %

12 %

45 %

57 %

16 %

38 %

25 %

14 %

53 %

31 %

80 %  Operation 60 % 40 %  Construction 20 %  Mobility 0 %

22 % 22 % New Conversions buildings Total primary energy

30 % 30 % New Conversions buildings Non-renewable primary energy

The most comprehensive attempts so far to map the sustainability aspects of buildings have been made by labels designed for the international property market, such as the British BREEAM, the German DGNB seal and the U.S. LEED certificate. Their evaluation matrices therefore contain a wide range of social, economic and environmental indicators, which are not equally easy to measure. However, the SIA recommendation 112/1 ‹Sustainable construction – buildings› can be considered to be at least as comprehensive a sustainability assessment, despite the fact that it can only be used qualitatively. The range of criteria to be considered for the building,

31 % 31 % New Conversions buildings Greenhouse gases

location or use seems enormous, but it should also be noted that a sustainable building that is fit for the future can achieve a great deal more than simply meeting high demands of energy efficiency, comfort and building ecology.


22  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 9: Source: Amt für Hochbauten, Stadt Zurich (Department for Buildings, City of Zurich)

Sustainability in construction Society

Environment

Economy

SIA recommendation 112/1 ‹Sustainable construction – buildings› SIA booklet 2040 ‹SIA path to energy efficiency› Eco Wellbeing, health Indoor air Lighting Noise

Embodied energy, building materials Raw materials, availability Material flows Environmental impact Deconstruction

Building stock Flexibility Operating and maintenance costs Accessibility System separation

Minergie-P Comfort Thermal comfort Heat protection in summer Systematic air renewal

Operating energy Indoor climate, building envelope Hot water Household appliances Lighting

Operating equipment Infrastructure (mobility) Choice of location Incentive systems Technical equipment

Community Design Use and access Safety

Refuse Water Soil, landscape

Investment costs Operating costs Life cycle costs


23 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.2

Contemporary and sustainable heat generation and intelligent building technology

Nearly 45 % of Switzerlandʼs primary energy is consumed by buildings. This high percentage suggests that major savings are possible. It is necessary to increase the overall efficiency of the construction, operation and deconstruction of buildings and to use more renewable energy to generate heat. Wood and the sun are indigenous energy sources that complement each other ideally in the area of heating and are very versatile. 4.2.1 Wood energy in general For millennia wood was the only energy source actively used by humans. Since the Industrial Revolution, however, fossil fuels and electricity have gained increasing importance. In Switzerland today, there are around 635 000 wood heaters of all categories (not including open fireplaces) installed. They produce, according to the Swiss Wood Energy Statistics 2009, a total of 6900 GWh of thermal and 150 GWh of electrical energy. They thus cover about 4 % of total Swiss energy consumption, or about 8 % of the heating market. Wood energy is the second most important domestic energy resource, after hydroelectric power. With the additional use potential of forest wood, waste wood from woodworking operations, non-forest wood from landscape and tree care, and post-consumer wood, todayʼs wood energy use could be increased by about half, without competing with higher-value product lines. As mentioned in Section 1, the objectives of Swiss energy policy include a reduction in the use of fossil fuels and a decrease in CO2 emissions to below 1990 levels. Wood energy plays an important role here. Due to the massive increase in energy efficiency in the Swiss building stock it is conceivable that wood will one day heat about a quarter of Swiss buildings. 4.2.2 Firewood The oldest way of using the energy of wood is the burning of firewood. Firewood as defined by the Swiss Clean Air Act refers to pieces of wood in its natural state, including the bark adhering to it, in particular split logs, wood briquettes, brushwood and cones. Well-dried and stored, it is still an innovative fuel that can be used in many ways: as an additional source of heating in living rooms, as total heating in energy efficient homes or as a boiler variant in the basement. Proper storage and conditioning of firewood is very important for clean combustion. The humidity must not exceed 20 %, which is achieved in 1– 2 years when the wood is stored in a sunny place with good air circulation, protected from rain and ground humidity. Correct firing is the second condition for low-emission wood heating.

4.2.3 Woodchips The smallest woodchip heating systems are available with outputs from 20 kW and above and are suitable for larger single or multi-family dwellings and for smaller businesses. Woodchip furnaces are mainly in use in the power range 200 kW to 2 MW and are often combined with a heating network. Woodchips are suitable for automatic fuel feed and are burned in an underfeed furnace or grate stoker furnace. Underfeed furnaces are used in the lower power range and require pre-dried wood chips with a water content of max. 35 %. Grate stoker furnaces can also burn undried wood chips with a fresh water content of up to 60 %. Raw materials for wood chips are energy wood from the forest, wood from landscape conservation, waste wood from forest thinning and, for suitable heating systems, also waste wood from woodworking operations. If waste wood is used, the heating system is subject to a measurement requirement. Woodchips are temporarily stored in appropriate storage facilities for drying. 4.2.4 Pellets 1998 saw Switzerlandʼs first automatic wood heating system using wood pellets, a standardised fuel made of wood. Pellets for central heating systems and pellet stoves have a diameter of 6 – 8 mm and a length of 5 – 45 mm. They consist mainly of sawdust and shavings from untreated wood. This valuable resource is pressed through a die at high pressure, dry and without addition of binders. The lignin contained in the wood is mobilized by frictional heat during pressing and then holds the pellets together. One kilogram of pellets contains almost as much energy as half a litre of oil. Thanks to their high energy density, pellets use only half as much storage capacity as well dried firewood, for the same amount of energy. Tailor-made solutions thanks to 4.2.5  sophisticated technology Modern, properly operated wood heating systems achieve maximum efficiency with minimum emissions and meet the strict limits of air pollution control regulations without difficulty. The following diagram shows the procedure for choosing the right heating system.


24  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 10: Procedure to choose the right heating system

The way to optimal wood heating Heating requirement and Wood as an additional fuel readiness for effort involved with manual loading in operation Indoor climate requirements ‹Wood fire atmosphere› Reduced comfort demand

Wood as the main fuel with manual loading

Wood as the main fuel with automatic operation

20 °C everywhere, at all times

20 °C everywhere, at all times

Building category

Individual rooms Individual storeys Detached houses

Detached and terraced houses Smaller apartment buildings

Detached and terraced houses and apartment buildings Public buildings Estates, complexes District heating networks

Type

Wood-burning fireplace Stoves, fireplaces Tiled stoves Wood cooking stoves Pellet stoves

Wood-burning fireplace Central heating cooking stove Tiled stove with hot water production Central heating boiler /  storage tank

Wood-burning fireplace inserts Pellet heating Underfeed combustion Step grate combustion Injection furnace

Combination with solar energy

Yes

Yes

Yes

4.2.6 Solar and wood heating combined Solar collectors in the form of flat or vacuum collectors are used for heat recovery from solar energy. The central elements are solar collectors in the form of absorbers directed towards the sun, which temporarily store the absorbed heat in an energy storage device. Solar energy is used for heating hot water and can also support space heating. Glazed flat plate collectors are normally used for the recovery of solar energy. When the exposure of facades and roofs to the sun is sub-optimal, vacuum collectors are recommended. The combination of wood and solar energy is possible in many different applications. The symbiosis of these two renewable energy sources in single and multifamily dwellings is well-known. Efficiency can be maximized by the optimal combination of their strengths and weaknesses. In summer, when the sun shines with high intensity, it makes no sense to use a wood heater. In winter, though, the opposite is true. The integration of solar systems into combined heating systems operated with wood chips or pellets is not yet common in Switzerland. The community of Coldrerio (canton of Ticino) implemented a combined heating system for its publicly owned buildings a few years ago. Although a gas network was available and a few municipal buildings were already heated with gas, Coldrerio opted for wood chips. This local energy source is abundant in the canton of Ticino, where forest accounts for 52 % of the total area.

Today the local community offices, kindergartens, primary schools, multipurpose buildings, gym and changing rooms of the sports ground are connected to the heating network. To meet the demand for hot water in the changing rooms in summer, 30 m2 of solar thermal collectors were installed on the roof of the gym. The other buildings connected to the heating network have a very low demand for hot water and it is produced locally. This means that the heating system, with a 550 kW chip boiler supported by a 126 kW gas boiler at peak load times, only needs to be in operation during the heating season, so that inefficient partial load operation outside the heating season is eliminated. In winter, the solar energy collected is fed into the heating network and helps reduce the need for woodchips. To achieve minimal particle emissions, the plant is equipped with an electrostatic precipitator for dust. In Coldrerio, 85 % of the community’s buildings are heated by the combined heating system.


25 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.2.7 Emissions Wood heating systems emit particulate matter, but there are major differences − on the one hand in the type of firing (automatic or hand-fed) and on the other in the age of the system. The technology of wood heating systems has made great progress in the past 20 years: thermal efficiency has been progressively improved and dust emissions significantly reduced. In addition, dust emissions can now be further reduced by secondary measures. These are now available for the entire spectrum of wood energy use and cover all performance categories, from log fires in living rooms to large automatic boilers. For example, simple electrostatic precipitators are available for living room fireplaces, while fabric filters, flue gas scrubbers (wet cleaning) and plate precipitators are options for large systems. Enough time must be allowed for considering these secondary measures, even in the early stages of planning. 4.2.8  The Swiss Clean Air Act (LRV) and energy policy objectives The Swiss Clean Air Act (LRV) describes the emission limit values and the required quality of all fuels, including wood energy. For example, it stipulates that wood heating systems with outputs higher than 70 kW may not emit more than 50 mg of dust per standard cubic meter (nm3). For wood furnace heating systems with a capacity greater than 500 kW, the limit is 20 mg / nm3. The furnaces must be appropriately equipped with fine dust collectors. The use of

Figure 11: Solar thermal collectors on the roof of the Coldrerio gym

Figure 12: Filling Coldrerioʼs combined heating system with wood chips Figure 13: Particle separator for a small wood heating system

wood energy is an important factor in achieving the goals of Swiss federal climate policy, such as the reduction of greenhouse gases. Efficiency and renewable energies assume a symbiotic relationship in this context. However, so-called action zones can limit the use of wood energy, especially in urban areas. Dust and odour emissions are far more strongly weighted here than in other areas. The main alternatives to wood are heat pumps, which work with ambient or geothermal energy. The use of heat pumps involves no particulate matter, and they can even be used for summer cooling (passive geothermal systems). The use of renewable energies and an increase of efficiency in the building stock is essential for the achievement of the 2000-watt society. This requires a sensible combination of all renewable energy sources, be it for power generation or for heat recovery. In this regard, the Swiss Clean Air Act (LRV) ensures that the use of wood energy must take place in a context in which state of the art technical facilities are in use, and where there are therefore no health concerns.


26  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3 Building construction from the perspectives of energy, ecology and comfort

Transmission heat losses Solar gains

In the booklet ‹Element 29 – Wärmeschutz Hochbau› (Heat insulation in buildings) (2010, Faktor Verlag) the authors Thomas Frank and Dr. Andreas Queisser discuss dynamic simulation and make the following statements: ‹The behaviour of thermal processes in buildings is naturally time-dependent, i. e. non-stationary. Common stationary accounting models based on U-values, for example, the method based on the standard SIA 380/1 ‹Thermal energy in buildings›, are therefore unsuitable for making statements on real comfort or on heating and cooling needs. To calculate the temporal profiles of temperatures and heat flows, dynamic simulation models are required which are able to map the heating behaviour of a building and its technical equipment realistically. In particular, the benefits of solid construction in terms of comfort and the use of solar energy gain, and the effects of heat storage behaviour can only be demonstrated realistically using dynamic models.› Moreover, they state, based on a reference calculation, that the heating requirement determined by dynamic calculation is about 10 % lower than in the (simplistic) statistical calculation based on the standard SIA 380/1 ‹Thermal energy in buildings›: ‹Dynamic building simulation thus enables a realistic assessment of both the achievable energy gains and the resulting comfort conditions, which a purely static, U-value-focused approach cannot achieve. The advantages of solid construction with respect to energetic performance and comfort can be quantified using this method.› Without a direct comparison with other construction methods, however, the question remains unanswered as to whether the differences between solid and light construction, and between a simplified view based on the standard SIA 380/1 ‹Thermal energy in buildings› and more detailed analysis by means of dynamic simulation are actually significant. In addition, questions on embodied energy and the carbon footprint must also be asked in connection with the thermal efficiency of buildings. How do the various methods of construction and insulation standards stand in this regard?

Internal gains

Ventilation heat losses

Figure 14: Energy flows in buildings

Comprehensive assessment for fair statements The following study, based on the example of an apartment building complex, addresses this issue. The comfort and thermal characteristics are considered in correlation with the embodied energy and CO2 effects, in an interdisciplinary way and for various construction methods:  Influence of the three methods of construction ‹light› (timber frame construction), ‹medium› (solid timber construction) and ‹heavy› (masonry construction)

Influence of the energy standards of the minimum legal requirement MuKEn, up to the Minergie-P standard Stationary evaluation of the energy flows, with calculation according to standard SIA 380 / 1 ‹Thermal energy in buildings›, using dynamic simulation (multi-zone model with IDA ICE) and evaluation of comfort in summer via dynamic simulation Determination of the influence of the construction method and energy standards on the ecology regarding the criteria of embodied energy and greenhouse gas potential  Using the overall view ‹construction and operation›, from construction to deconstruction, the study shows how efficient the change from the insulation standard MuKEn to Minergie P is, in relation to different energy scenarios and the methods of construction ‹light› to ‹heavy›. Questions to be answered The extensive investigations provide answers to important questions for construction practice: Does stationary observation based on the standard SIA 380/1 ‹Thermal energy in buildings› correspond to reality, or are relevant differences ascertainable upon closer inspection using dynamic simulation?  Are the differences between the standard SIA 380/1 ‹Thermal energy in buildings› and the dynamic simulation of construction methods ‹light› to ‹heavy› significant, and does solid construction really show advantages over timber construction, as is sometimes suggested in publications, when a differentiated examination, allowed by dynamic simulation, is made?  How does the construction method affect the temperature profile in a ‹critical space› in the summer months, and how is the need for cooling evaluated? Do advantages regarding embodied energy in various construction methods outweigh possible disadvantages in operating energy, and how should the construction methods be assessed from the ecological point of view?  Which is the energetically and environmentally most efficient construction method, and to which energy standard should it be executed?


27 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3.1 Reference property Hegianwandweg The ‹Hegianwandweg› housing project on the outskirts of Zurich is used to study the effects of different construction types on energy, ecology and comfort. This building complex, constructed with wood and other materials and technologies on behalf of the Zurich family home cooperative FGZ, has proven itself in its actual construction form, but could also easily be built using other methods, and is therefore an ideal reference building. The reference building studied consists of a solid basement and four or five residential floors in timber frame construction, which are arranged around a solid core with connecting areas and wet rooms (cf. figure 17). The intermediate floors are made of laminated timber with suspended ceilings and footfall-sound-insulated

Figure 15: Reference property ‹Hegianwandweg› with entrance area and outer walls in timber frame construction with rear-ventilated plaster base board

Figure 16: Reference building ‹Hegianwandweg› with balconies and the exterior walls behind them in timber frame construction with rear-ventilated gypsum fibre board

floor surfacing. The exterior walls consist of wood frame elements with flexible facing formwork on the inside and rear-ventilated cladding on the outside. The room and party walls are light and non-load bearing. The buildings, completed in 2003, are certified to Minergie standards. In comparison with the more stringent requirements of ‹MuKEn 08› the reference building, with 111 MJ/m2a, falls just short of the current applicable limit of 107 MJ/m2a. Further information on this interesting building complex can be found in the Lignum ‹Holzbulletin› 73/2004 and in a supplement to the journal ‹Hochparterre› 10/2003.


Climate-friendly and energy-efficient construction 28  with wood – Basic information and implementation

Figure 17: Floor plans, cross-sections and facades

Reference building ‹Hegianwandweg›

Longitudinal section

Basement

Northwest façade

Ground floor

Southeast façade

1st to 3rd floors

Southwest façade

Attic floor

Northeast façade


29 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3.1.1 Evaluation of the thermal building envelope according to the standard SIA 380/1 ‹Thermal energy in buildings› In evaluating the thermal building envelope according to the standard SIA 380/1 ‹Thermal energy in buildings›, the influence of the construction method on the utilisation of free heat is considered only with respect to the designations ‹very light› (metal building systems) to ‹heavy› (solid construction). The following definitions apply:  ‹heavy› (heat storage capacity 0.5 MJ/m2K): At least two of the three thermally active elements (ceiling, floor, all walls) are solid and without cover. ‹Medium› (heat storage capacity 0.3 MJ/m2K): At least one of the three thermally active elements (ceiling, floor, all walls) is solid and without cover. As defined by the standard SIA 380/1 ‹Thermal energy in buildings›, solid timber construction falls into this category.  ‹Light› (heat storage capacity 0.1 MJ/m2K): No requirements of thermally active elements. As de-

Figure 18: For the Minergie-P standard to be achieved with practicable construction methods, the thermal envelope for the simulation has been slightly modified in comparison to the reference project ‹Hegianwandweg›. In the basement, access areas are also within the thermal envelope. The U value of 2.5 W/m2K, to be observed for the standard SIA 380/1 ‹Thermal energy in buildings› for ‹cavities› (stairs / elevator) would be too great a hurdle for Minergie P.

fined by the standard SIA 380/1 ‹Thermal energy in buildings›, timber frame construction falls into this category. However, according to the definition of the Minergie agency for buildings, the heat storage capacity in wooden buildings can be accepted as 0.3 MJ/m2K and thus the construction method ‹medium› can be applied when underlay flooring of not less than 60 mm cement screed or 50 mm anhydride screed is used and the walls on the room side are faced with 2 x 12.5 mm plasterboard or at least 18 mm gypsum fibre boards of medium raw density. The structural design of components for the simulation is chosen so that the relevant limits are met: MuKEn with Qh = Qh,li Minergie-P with Qh = 0,6 x Qh,li The characteristics over time of the thermal building envelope have been slightly modified compared to the reference project ‹Hegianwandweg› (cf. figure 18).

Plans of the basement and ground floor of the reference building ‹Hegianwandweg› ‹Hegianwandweg› project

Project variants ‹light›, ‹medium› and ‹heavy› for MuKEn and Minergie-P

Basement

Ground floor

innerhalb der thermischen Gebäudehülle Additional building components with heat insulation layers: ausserhalb der thermischen Gebäudehülle

zusätzliche Bauteile mit Wärmedämmschichten: – Boden über Erdreich mit Schaumglasschotter Soil on ground with foam glass 200 mm (MuKEn) or 400 mm (Minergie-P) 200 mm (MuKEn) bzw. 400 mm (MINERGIE-P) – Wände gegen unbeheizte Räume mit Verbundplatte Walls to unheated rooms with 90 mm (MuKEn) or 150 mm (Minergie-P) composite panels 90 mm (MuKEn) bzw. 150 mm (MINERGIE-P) Additional door seal to unheated rooms – Zusätzlicher Türabschluss gegen unbeheizte Räume

Inside the thermal building envelope


Climate-friendly and energy-efficient construction 30  with wood – Basic information and implementation

4.3.1.2 Construction methods investigated The existing construction method of the reference building ‹Hegianwandweg› is ‹light› according to the standard SIA 380/1 ‹Thermal energy in buildings›. In addition, the quality of the windows / glazing and the thickness of the insulating layers has also been adjusted to the extent that the minimum thermal insulation is maintained according to MuKEn in one

Structures of the reference building ‹Hegianwandweg› and variants for comparison ‹Hegianwandweg› construction method

‹light› construction method

‹medium› construction method

‹heavy› construction method

Outer walls

180

40

180 320

40

160 260

80

180 260

150

Windows Wooden windows with triple glazing Ug = 0.7 or 0.6 W/m2K g = 47 % Bezel steel or plastic

Wooden windows with double glazing Ug = 1.0 W/m2K g = 65 % Bezel steel

Wooden windows with triple glazing Ug = 0.7 or 0.6 W/m 2K g = 47 % Bezel steel or plastic

Wooden windows with triple glazing Ug = 0.7 or 0.6 W/m 2K g = 47 % Bezel steel or plastic

140 240 220

140 240 220

180

220

180

220

180

160

160 260

Flat roof above 4th floor

80 100

80 100

250

100 120

180

180

100

100 160

Flat roof above 3rd floor

250

100

60 20 120 250

250

250

60 20 120

120

220 60 20 160

220 250

60 20

Soil above basement

200

Storey ceilings 200

Figure 19: In addition to the actual thickness of the insulating layers in the reference building, those are given which are necessary to reach the limit values of MuKEn or Minergie-P. With flat roofs and intermediate floors, some different structures are used in timber frame construction in the living area (shown on the left) and in the access zone (shown on the right).

variant, and in a second variant the high demands on the thermal envelope for Minergie-P (40 % below the MuKEn limit ) are observed. As an alternative construction method, solid timber construction (‹medium›) and solid construction (‹heavy›) are studied, also using the standards MuKEn and Minergie P (cf. figure 19).

Interior walls and partition walls

var.

var.

  Wood and wooden composites  Concrete  Brick

var.

var.

80

  Mineral materials   Gypsum- / gypsum fibre boards   Stone chips

80

80

var.

  Mineral wool   XPS / EPS insulation

180

75


31 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3.2  Dynamic simulation of thermal properties The simulation program IDA ICE 4.0 provides a detailed building model for the study of thermal influences. Through thermal-dynamic simulations the complex relationships in a building are recorded and mapped as realistically as possible. The heating demand, heating output or lighting are not considered as separate criteria; rather, all relevant factors with their interactions are taken into account as total systems. This allows total energy evaluation or optimization of a building and an evaluation of comfort, for example with respect to the temperature gradient in critical areas (summer overheating). The simulation model is created on the same project basis as the standard calculation according to the standard SIA 380/1 ‹Thermal energy in buildings›, but internal components (floors, interior walls) are taken into account, as is the actual building construction, with all its layers and building material characteristics (such as

Figure 20: The colours of the zones correspond to the maximum expected room temperature over a year. The top floor, for example, comprises three residential units with a total of 11 zones.

thermal conductivity, gross density and heat storage capacity). Thus, the heat storage capacity of each component in the simulation is considered dynamically. For the simulation, the building is divided into different thermal zones. In the zoning the individual residential units, their orientation and use, and the corresponding internal loads, can be modelled in detail. Internal loads and the use of passive solar gains play a major role in the calculation of the heating demand. It is therefore important to account for the resulting heat gains correctly. For this reason, each residential unit is divided into three to four zones so that different uses and orientations of the rooms can be depicted realistically in the simulation.

Three-dimensional simulation model with a vertical and a horizontal section through the reference building ‹Hegianwandweg› Maximum temperature [°C] 26.5

26.0

25.5

25.0 N S

24.5

Internal loads (people, appliances, lighting) The internal loads are taken from the SIA booklet 2024 ‹Standard conditions of use for energy and building services›. The occupancy of the units, the appliance loads and the maximum installed lighting output per use are defined according to the project. In contrast to the standard SIA 380/1 ‹Thermal energy in buildings› the heat output of people is not taken as having a constant standard value; the simulation takes into account the actual heat output of the occupants in relation to room temperature, activity, clothing, temperature of the surroundings and room humidity. Lighting is calculated in the simulation as a function of

usable daylight and the persons present at a set point of 200 lux, and the resulting output included in internal loads; this is significantly more differentiated than the use of default values in the standard SIA 380/1 ‹Thermal energy in buildings›.


Climate-friendly and energy-efficient construction 32  with wood – Basic information and implementation

Space heating All the variants examined (light to solid construction to the standards MuKEn and Minergie-P) were simulated with a floor heating system. The floor heating is defined and regulated for all zones so that a desired value of 21 °C is reached. This desired value was chosen for the simulation to ensure that with a control deviation of ± 1 K, the room temperature never drops below

Figure 21: The diagram on the left shows the clear differences in ambient air temperature between the variants MuKEn and Minergie P in the ‹light› construction method. On the right side the behaviour of the room temperature as a function of the construction method is shown for the Minergie-P standard: only minimal differences can be seen.

20 °C. The average room temperature throughout the building is therefore considered to be 1 K higher than in the calculation according to the standard SIA 380/1 ‹Thermal energy in buildings›, which specifies a default value of 20 °C.

Outdoor and room temperature and global radiation data in the course of a typical winter week Comparison of the energy standards with ‹light› construction method

Comparison of the construction methods with Minergie-P

Temperature [ °C ]

Temperature [ °C ]  Solar radiation [ W / m2 ]

Solar radiation [ W / m2 ]

24

24

22

22

20

3000

20

18

18

16

16

14

14

12

3000

12

10

2000

10

8

8

6

6

4

4

2

2000

2

0

1000

0

–2

–2

–4

–4

–6

–6

–8

1000

–8

– 10

0

– 10

1 Jan. 2 Jan. 3 Jan. 4 Jan. 5 Jan. 6 Jan. 7 Jan. 8 Jan.   MuKEn

  Minergie-P

0 1 Jan. 2 Jan. 3 Jan. 4 Jan. 5 Jan. 6 Jan. 7 Jan. 8 Jan.

  ‹light›

construction method construction method

 ‹heavy›

construction method

 ‹medium›   Radiation

  Outside

temperature

Ventilation / Infiltration The loss of ventilation via infiltration is considered in the simulation, as in the standard SIA 380/1 ‹Thermal energy in buildings›, as a constant exchange of air. In addition, some of the windows are opened when the room temperature reaches 24 °C. In this way the rooms are cooled by natural window ventilation. The windows are opened in the simulation to the extent that a two- to threefold replacement of air is achieved.

With the Minergie-P variants comfort ventilation is also simulated, in addition to natural infiltration (adapted to the denser building envelope). Each room is considered to have a volume flow of 20 m3/h, and 40 m3/h is allowed for the living room. The exhaust air is discharged as usual in the kitchen and the wet rooms. The ventilation system has heat recovery with a bypass valve and is in operation throughout the year.


33 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3.2.1 Model according to the standard SIA 380 / 1 ‹Thermal energy in buildings› calculates on the safe side In Switzerland heating demand is usually calculated using the standard SIA 380/1 ‹Thermal energy in buildings›, which is also the basis for the certifications Minergie and Minergie-P. Nevertheless, dynamic simulation has clear advantages over the stationary calculation model according to the standard SIA 380/1 ‹Thermal energy in buildings›, as is emphasised in the previously mentioned Element 29 ‹Heat protection in buildings›, for example. Using complex dynamic simulations, which model the actual structures and their thermal storage behaviour and take into account climatic conditions using hourly averages, ‹the true situation› can be more realistically represented than through the use of stationary methods. The calculations made in this study show that the simple stationary evaluation model of the standard SIA 380/1 ‹Thermal energy in buildings› shows a heating

Figure 22: Explanation of the differences in heat demand calculated according to the standard SIA 380/1 ‹Thermal energy in buildings› and the dynamic building simulation

demand which is slightly higher than that calculated by the dynamic simulation, and is thus on the ‹safe side› (cf. figure 23). The heating demand specified in the standard SIA 380/1 is estimated at about 5 % higher. If in the dynamic simulation, the room temperature of 20 °C is not defined as the lower threshold, but as an average, the divergence between the standard SIA 380/1 and the simulation can be as high as 10 %. Allowing for an average room temperature of 20 °C, however, leads in individual rooms to lower room temperatures (e. g. in north-facing zones), which is hardly acceptable for reasons of comfort. The difference in the calculated heating requirement is justified by the following assumptions, among other factors:

Comparison of heat demand Standard SIA 380/1 ‹Thermal energy in buildings›

Dynamic building simulation

The heat storage capacity and thus the use of free heat (e. g. passive solar gains) is only estimated using a rough classification of the construction type (‹very light› to ‹heavy›).

The existing building component layers with their mass and heat storage capabilities are considered.

The losses and gains over twelve months are reported. Monthly mean values are assumed for the outdoor temperatures and standard values for the room temperatures, e. g. 20 °C as a constant for residential properties.

The energy flows are recorded by the hour, allowing for a variety of influences, e. g. on the room temperature. If an average room temperature of 20 °C is simulated, the actual values may drop below this at times – with a correspondingly lower heating demand than if the room temperature were never allowed to fall below 20 °C.

Only fixed shading by the horizon, the canopies and the side panels is taken into account and it is thus assumed that in the cold season the user will admit energy gains from solar radiation and will not reduce them by using the variable solar protection.

The solar protection is operated according to the global radiation. It may, therefore, occur that on a fine winter day with high global radiation, the solar protection comes into operation.

In the data commented on below, the simulation for the ‹light› construction method leads to a minimum room temperature of 20.2 to 20.7 °C, depending

on the room (MuKEn or Minergie-P), although on intermediate storeys the minimum temperatures are 20.6 °C to 21.0 °C.


34  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.3.2.2 Advantageous construction methods depending on the heating demand The timber construction method defined as ‹light› in the standard SIA 380/1 ‹Thermal energy in buildings› shows its true quality in energy terms when it is evaluated by means of dynamic building simulation: the actual storage capacity available, in comparison to the figures calculated according to the standard SIA 380/1, leads to a heating demand that is 11 % lower. A comparison of the construction methods ‹light› to ‹heavy› in the MuKEn and Minergie-P standards, calculated using the standard SIA 380/1 and dynamic building simulation, leads to the following conclusion:

Figure 23: Comparison of heating demand Q h in MJ/m2a for the construction methods investigated according to the standards MuKEn and Minergie-P, with the values taken from the dynamic calculation and those taken from calculation according to the standard SIA 380/1 ‹Thermal energy in buildings›

Heating demand Qh for different construction methods MuKEn Minergie-P MuKEn 120 

With correct assignment of the construction methods ‹light› to ‹heavy› according to the standard SIA 380/1 ‹Thermal energy in buildings›, the calculated differences in heating demand are identical regardless of the construction method, at approximately 5 % for the MuKEn standard and about 3 % for Minergie P (cf. figure 23 and figure 24). It is therefore clearly not the case that only ‹heavy solid construction› according to the standard SIA 380/1 ‹Thermal energy in buildings› is wrongly evaluated and that its quality in terms of heat storage capacity and utilization of solar gains can only be correctly assessed using dynamic building simulation. The timber constructions studied also prove their qualities through the differentiated analysis achieved through dynamic building simulation.

Minergie-P

MuKEn

– 5 %

Minergie-P – 4 %

– 11 %

100  80  60  40    20 

– 3 %

– 13 %

– 3 %

0    ‹light› construction method

‹medium› construction method

‹heavy› construction method

  Heating

demand Qh = Qh, li (MuKEn) according to SIA 380/1 ‹Thermal energy in buildings› calculation demand Qh = based on dynamic building simulation (MuKEn with standard air change, Minergie-P with heat recovery ventilation)   Heating demand Qh = 0.6 x Qh, li (Minergie-P) according to SIA 380/1 ‹Thermal energy in buildings› calculation  Heating demand Qh, eff = with heat recovery ventilation (Vth = 0.28) according to SIA 380/1 ‹Thermal energy in buildings› calculation (Minergie-P)   Heating

Using the MuKEn standard, the heating demand normally calculated according to the standard SIA 380/1 is 4 – 11 % higher than that determined through dynamic simulation. The significant deviation of 11 % for the ‹light› construction method can be easily explained: in fact this construction method has a heat storage capacity which approximately corresponds to the ‹medium› construction method, whereby the heating demand

according to the standard SIA 380/is reduced to 100 MJ/m2a, which is then only 5 % higher than that calculated by dynamic simulation (cf. also figure 24). For Minergie-P the deviation of 13 % between the standard SIA 380/1 and the simulation is considerably higher than the 3 % deviation for the ‹medium› and ‹heavy› construction methods, due to the incorrect attribution of timber construction to the ‹light› category.


35 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 24: Heating demand Qh in MJ/m2a. The same thermal building envelope, assessed according to the SIA 380/1 standard and only influenced by the heat capacity of the construction method (‹heavy› to ‹very light›), shows a heating demand of 99 – 115 MJ/m2a. The heating demand for the ‹light› construction method, or the demand dynamically simulated for the actual building construction of the reference project ‹Hegianwandweg› is 95 MJ/m2a.

Heating demand Qh according to the standard SIA 380/1 ‹Thermal energy in buildings› depending on the classification of the timber frame construction method 115 120  107

100 

100

– 17 %

– 11 %

‹very light› construction method

‹light› construction method

99 – 5 %

– 4 %

80  60  40    20  0    ‹medium› construction method

‹heavy› construction method

 Heating

demand Qh = Qh, li (MuKEn) according to SIA 380/1 ‹Thermal energy in buildings› calculation, depending on the construction method   Heating demand Qh = based on dynamic building simulation

Whether the ‹light› or ‹medium› construction method is selected is critical for the evaluation of timber structures. This is particularly so because in these structures the calculated difference in heat demand is very high, while the difference between ‹medium› and ‹heavy› is still only negligible. In fact the timber construction allocated to the ‹light› category corresponds more closely to the ‹medium› category, whereby the divergence between the standard SIA 380/1 ‹Thermal energy in buildings› and the dynamic simulation – about 5 % – is identical for each of the construction methods. 4.3.2.3 Comfort in summer dependent on the construction method Modern residential buildings, such as the ‹Hegianwandweg› complex, have large window areas for passive solar heat gain. The solar gains that are desirable in the winter months may, however, jeopardise comfort in the summer. Rooms with high proportions of glass and low thermal storage mass tend to overheat in the summer. This problem is addressed in various SIA standards and in the Minergie(-P) standard. Minergie bases its demands regarding heat protection in summer on the current SIA 382/1 standard ‹Ventilation and air conditioning systems – general information and requirements›. This standard defines the number of hours a room temperature may be above the variable threshold (26.5 °C to 24.5 °C depending on the maximum exteri-

or temperature). If this temperature is not exceeded, no cooling is required. In rooms where the limit temperature is exceeded for up to a maximum of 100 hours per year, cooling is desirable. If the temperature is above the limit established in the standard SIA 382/1 ‹Ventilation and air conditioning systems – general information and requirements› for more than 100 hours, cooling is mandatory. The detection method is described in detail in the standard and can by implemented by means of thermal simulation, for example using IDA ICE 4.0. Temperature data for a summer week In a typical summer week, the outside air temperature fluctuates in a range from 15 °C to 33 °C. When the sun shines, a global radiation of about 900 W/m2 is achieved. Figure 21 shows the room temperatures of the living room on the 2nd floor, facing south and west. In the construction methods ‹light› and ‹medium› the room temperatures vary between 22.0 °C and 27.5 °C. The ‹heavy› construction has a maximum room temperature about 2 K lower than the two lighter construction methods; the temperatures vary within a range of about 22.0 °C to 25.0 °C.


36  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 25: The room temperatures of the two designs ‹light› and ‹medium› differ very little. With the ‹heavy‹ construction method a maximum room temperature of about 2 K lower an be achieved.

Outdoor and room temperature and global radiation data in the course of a typical summer week Temperature [ °C ]

Solar radiation [ W/m2 ]

34

2400

32 30

2000

28 26

1600

24 22

1200

20 18

800

16 14

400

12 10

0 18 July

‹light› construction method

19  July

20 July

21 July

22  July

‹medium› construction method

  MuKEn

  MuKEn

  Minergie-P

  Minergie-P

  Radiation

  Outside

23 July

24 July

25 July

‹heavy› construction method

  MuKEn   Minergie-P

temperature

Statistical analysis of room temperatures in summer The requirement in the standard SIA 382/1 ‹Ventilation and air conditioning systems – general information and requirements› that the variable temperature limit value may be exceeded for less than 100 hours per year, can be met in all the variants. There is therefore no need to condition the rooms with a mechanical cooling system. The maximum ambient air temperatures expected in the construction methods ‹light› and ‹medium› are in the range 26.5 °C to 27.5 °C. In the ‹heavy construction method› the maximum values are about 2 K lower; air temperature rises to a maximum of 25.5 °C (cf. figure 26). In addition to the evaluation of hours with excessively high air temperatures according to the standard SIA 382/1 ‹Ventilation and air conditioning systems – general information and requirements›, the frequency of hours with temperatures above 26 °C was examined. The building with the ‹heavy› construction method› has no hours above 26 °C. In the ‹light› and ‹medium› con-

struction methods, 25 – 81 hours per year show temperatures over 26 °C, depending on the construction method and energy standards. The summer room temperature of 28 °C specified in the SIA booklet 2024 ‹Standard conditions of use for energy and building services› is not reached by any of the construction methods. It can therefore be concluded that all the construction methods comply with the standards’ requirements for summer heat protection.


37 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 26: The maximum temperature of 28 °C according to the SIA booklet 2024 ‹Standard conditions of use for energy and building services› is not reached by any of the variants. The number of hours are also shown where air temperatures can be expected that are above the limit according to the standard SIA 382/1 ‹Ventilation and air conditioning systems – general information and requirements›, as well as the number of hours with an ambient air temperature of more than 26 °C. With a maximum of 81 hours over the limit cooling is not mandatory, although it is desirable, even for the construction method ‹light› / Minergie-P.

Evaluation of the maximum expected room temperatures depending on construction and energy standards Maximum temperature for a summer week [ °C ]

MuKEn

Minergie-P

Hours with excess temperature [ h ]

MuKEn

Minergie-P

MuKEn

Minergie-P

28

80

27  26

60

25 24

40

23 22   21 

20

‹light› construction method

‹medium› construction method

‹heavy› construction method

  Maximum

temperature above limit value according to standard SIA 382/1 ‹Ventilation and air conditioning systems – general information and requirements›   Hours over 26 °C  Hours

Improvement through floor cooling The normative requirements for summer thermal protection can be met by all the construction methods and energy standards. However, the building with the ‹heavy› construction type has particular advantages regarding the maximum ambient air temperatures, which lead to greater comfort in the summer. The simulation is therefore used to show the influence of ‹desirable cooling› on the summer air temperatures, and thus whether the ‹light› construction method can be improved to such an extent that it is at least as good as the ‹heavy› method.

For cooling, the floor heating is used in summer as a cooling surface and the heat energy removed from the building is fed through the boreholes to an underground storage tank. Apart from the positive impact on room temperatures and comfort (cf. figure 27 and figure 28) the annual performance factor of the heat pump can thus be increased.


38  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 27: As the figure shows, the room temperatures in the light construction to the Minergie-P standard can be reduced by gentle floor cooling to the point that they are slightly lower than those of the ‹heavy› design.

Scatter diagram of ambient air temperatures set against the maximum daily outside temperatures Room temperature in [ °C ]

30 29 28 27 26

Limit value: standard SIA 382/1

25 24 23 22 21 20 5

10

15

20

25

30

Daily maximum outside temperature in [°C]

  ‹light› construction method Minergie-P   ‹medium› construction method Minergie-P with cooling or floor heating   ‹heavy› construction method Minergie-P

4.3.3  Environmental impacts of construction methods and energy standards 4.3.3.1 Methodology for considering the ecology Until a decade ago mere observation of heating demand provided a good criterion for making a statement on the energy performance of a building. With ever more effectively insulated building envelopes, however, the importance of heating demand in a total-energy approach is considerably qualified: the embodied energy needed to construct a building and the associated greenhouse gas emissions exceed the heating energy and emissions from the heating system many times over, when the entire life cycle of a building is considered. To enable a total energy approach, the three designs described – ‹light›, ‹medium› and ‹heavy› – were also examined with regard to embodied energy and greenhouse gas emissions for the reference building, in each case with an insulation standard that meets the requirements of MuKEn and the primary requirements of Minergie-P. The structures were used as shown in figure 19 and thereby correspond to the assumptions used to calculate the heating requirement.

To calculate the embodied energy and greenhouse gas emissions, surface and material figures were calculated for the entire building according to the SIA booklet 2032 ‹Embodied energy of buildings›. This energy required for construction includes the entire life cycle from raw material extraction to the production of building materials, transportation and disposal. The individual components are assigned an amortisation time. This also allows the construction energy to be shown by year and energy reference area, so that a comparison can be made between construction energy and operating energy.


39 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 28: The maximum room temperatures in the construction variant ‹light› to the Minergie-P standard, of 27 °C to 27.5 °C, can be reduced by gentle cooling using the floor heating and the borehole, by up to 3 K. With this simple cooling technique, even better comfort conditions can be achieved than in the ‹heavy› construction method.

Outdoor and room temperature and global radiation data in the course of a typical summer week Temperatur [ °C ]

Solar radiation [ W/m2 ] 34

2400

32 30

2000

28 26

1600

24 22

1200

20 18

800

16 14

400

12 10

0 18 July

‹Light› construction method

  Minergie-P

with cooling or floor heating   Radiation

19 July

20 July

21 July

22 July

23 July

24 July

25 July

‹Heavy› construction method

  Minergie-P

 Minergie-P

  Outside

temperature

4.3.3.2 Construction energy: embodied energy and greenhouse gas emissions It should be mentioned in advance that in the selected reference building the light construction method is better insulated than the solid construction method – in order to achieve the heating demand specified in the standard SIA 380/1 ‹Thermal energy in buildings› and to make up for the (supposedly) lower heat storage capacity of the light construction method (cf. figure 19). This means that the construction energy calculation for the light construction method includes the additional load of the greater insulation thickness. The effect is negligible, however. The fact that in the selected reference property the central zone in all three construction methods is built of concrete – as well as the basement, of course − has a certain influence on the results. This fact should not

be regarded as a falsification of the results, however: in an apartment building of the size of this reference property, fire protection and earthquake safety require that staircases are built using solid construction methods. In the basement solid construction is mandatory. Pure light construction in wood would therefore not be a realistic alternative for this comparison.


40  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 29: For all three methods of construction the basement and the central zone with staircase and wet rooms are built using solid construction methods.

Construction method of the basement and ground floor of the reference building ‹Hegianwandweg›

Basement

1st to 3rd floor

 Reinforced concrete walls (variable thickness) and concrete slab (250 mm) above ground   Sand lime brick walls 120 mm and 150 mm

Figure 30: Embodied energy in MJ/m2a from construction of the reference property ‹Hegianwandweg›, 25 calculated with Grisli 

  Brick walls 100 mm to 150 mm   Service and plumbing walls   Concrete slab and storey ceilings in reinforced concrete

Calculation of embodied energy Light construction method

Building under ground Exterior walls

MuKEn

Minergie-P

Solid timber construction method MuKEn Minergie-P

Solid construction method

8

11

8

11

8

11

7

8

9

11

10

12

24

23

24

24

25

MuKEn

Minergie-P

Windows, 23 balconies Ceilings, interior 16 walls Roofs 7

16

14

14

18

18

8

7

8

7

8

Interior fittings

19

20

22

23

19

20

Building services 18

22

18

22

18

22

Total

109

102

113

105

116

25 

100

Grisli, Instrument for calculating embodied energy and greenhouse gas emissions of whole buildings or building components, Büro für Umweltchemie, Zurich.


41 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 31: Greenhouse gas emissions in kg/m2a from the construction of the reference property ‹Hegianwandweg›, 25 calculated with Grisli 

Calculation of greenhouse gas emissions

Building under ground Exterior walls

Light construction

Solid timber construction

Solid construction

MuKEn

Minergie-P

MuKEn

Minergie-P

MuKEn

Minergie-P

0.8

0.9

0.8

0.9

0.8

0.9

0.4

0.4

0.5

0.6

0.6

0.7

1.6

1.7

1.6

1.7

1.8

1.8

Windows, balconies Ceilings, interior walls Roofs

1.2

1.2

1.3

1.3

1.8

1.8

0.4

0.5

0.4

0.5

0.5

0.6

Interior fittings

1.4

1.5

1.6

1.6

1.5

1.6

Building services 1.2

1.4

1.2

1.4

1.2

1.4

Total

7.6

7.4

8.0

8.3

8.8

7.1

The three construction methods compared When the three designs are compared, the lowest values for the construction phase are achieved for both embodied energy and greenhouse gas emissions with light construction, while a strictly solid construction method shows the highest values. This trend applies to both the moderate insulation standard according to MuKEn and to the high standard according to Minergie-P. Wood has excellent properties as a building material, while solid building materials produce higher values per square metre of component surface for both embodied and greenhouse gas emissions. Wood, as a renewable building material, generates hardly any production energy and, as it is locally produced, also comparatively little transportation energy. Although more insulation material was used in the reference building for the light method, in order to achieve the heating demand required by the standard SIA 380/1 ‹Thermal energy in buildings›, this variant remains unsurpassed in terms of construction energy. Despite the clearly discernible trend with respect to construction method, the differences should nevertheless be put into perspective. Regarding embodied energy a 5 % greater investment is required for solid construction than for the light method, while the greenhouse gas emissions for solid construction are around 16 % higher (with the same standard in terms of heat demand). The influence of the construction method is therefore smaller than is commonly believed. If complex, multi-layered systems are used for light construction, its advantages may even disap-

pear altogether. As expected, the values for solid timber construction lie in the middle – between light and solid construction. The influence of the construction method on the overall result should also be qualified in comparison to other influences, especially the shape and size of the building. The construction energy used per square metre of a small family house is up to 80 % greater than that required for a large and compact multi-family home – provided the same construction method is used. This applies to embodied energy as well as to greenhouse gas emissions. The crucial determinant for good results in construction is therefore not so much the construction method, but rather the size and shape of the building – i. e. the ratio between the building envelope area and the useful area it encloses. This also explains why for the calculated reference object, the values of all three construction methods are located in the area of indicative reference values according to the SIA booklet 2040 ‹SIA path to energy efficiency›: the reference building has an energy reference area of approximately 2500 m2 and is therefore of medium size and above average with regard to compactness. It is a building that has already been optimised with regard to construction energy. For a total energy analysis according to the SIA booklet 2040 the differences between the construction energy of the three methods of construction need to be relativized further. Although the percentage differences may not appear particularly large, they may nevertheless be crucial for the achievement of target values.


42  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Especially for greenhouse gas emissions, the budget for annual emissions available per square meter is small: for a new building in the ‹residential› category 16.5 kg/m2 is available for construction, total operation and site-dependent mobility, according to the SIA booklet 2040. Construction usually accounts for more than half this allowance. Around 8 kg/m2 per year remains for operation and mobility. One kilogram of greenhouse gas emissions saved during construction therefore decisively facilitates the achievement of objectives, when energy requirements are considered holistically. The construction energy for the two heating energy standards in comparison Comparing the values for the two heating standards MuKEn and Minergie-P (when the same construction method is used), the hardly surprising conclusion is reached that a building with a high insulation standard requires greater investments of embodied energy and greenhouse gas emissions than one with a moderate standard. The added expense of building the same design to the MuKEn and Minergie P standards can be explained by the greater insulation thicknesses, the more complex substructures of the façade cladding, and the higher quality windows. In the present calculation the construction energy for a ventilation system is also included for the Minergie P standard, which explains the differences in the building services. No ventilation system was included for the MuKEn standard. The added expense for the Minergie-P standard compared to MuKEn is around 10 % for the embodied energy and 7 % for the greenhouse gas emissions for the reference building. The additional expense for the high Minergie P standard is the same for all three construction methods. 26

SIA booklet 2040 ‹SIA path to energy efficiency›, June 2011. The non-binding reference values for the building category ‹residential› are 110 MJ/m2 and 8.5 kg/m2 per year.

4.3.4 Total energy perspective As an identical heating demand applies in the three construction methods for the reference property, according to the standard SIA 380/1 ‹Thermal energy in buildings›, a total energy analysis, in which heat energy demand and construction energy are offset against one another, is unnecessary. Regardless of which energy source is chosen for the heating system, the light construction method will always come out ahead, due to the lower values for construction. If the results of the dynamic calculation of heating requirements were taken as a basis for comparison, this tendency would be even more pronounced. In order to establish a relation between the magnitude of non-renewable primary energy and greenhouse gas emissions from construction (embodied energy and greenhouse gas emissions) and from the operation of the heating system, the heating energy must be converted to the corresponding level: the heating requirement (useful energy) must be divided by the efficiency of the heating system (final energy) and multiplied by the primary energy factors and greenhouse gas emission coefficients of the selected energy sources. The results are quite startling in their variance: with fossil fuels such as gas or oil the magnitude of the primary energy and emissions from the heating energy are comparable with the embodied energy and greenhouse gas emissions from the construction phase. In contrast, with renewable energy sources the primary energy and emissions from heating are negligible in comparison to emissions from construction. In other words this means: while for fossil fuels the higher cost of solid compared to light design at the construction phase can be easily offset by a slightly higher thermal insulation standard, this is not possible for a renewable energy source, considered from a total energy perspective.


43 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 32: Standard utilisation rates, primary energy factors and greenhouse gas emission coefficients according to the SIA booklet 2040 ‹SIA path to energy efficiency›

Non-renewable primary energy and greenhouse gas emissions with a heating demand of 107 MJ/m2 for different energy sources Energy source Gas Borehole heat pump 27 Woodchips

Energy source Gas Borehole heat pump 27 Woodchips

Heating demand (MuKEn), SIA 380/1 107 MJ/m2 a

Rate of utilisation

Primary energy factor

0.9

1.11 MJ/MJ

Non-renewable primary energy 132 MJ/m2 a

107 MJ/m2 a

3.9

2.64 MJ/MJ

72 MJ/m2 a

107 MJ/m2 a

0.75

0.06 MJ/MJ

9 MJ/m2 a

Heating demand (MuKEn), SIA 380/1 107 MJ/m2 a

Rate of utilisation 0.9

Greenhouse gas emission coefficient 0.066 kg/MJ

Greenhouse gas emissions 7.8 kg/m2 a

107 MJ/m2 a

3.9

0.041 kg/MJ

1.1 kg/m2 a

107 MJ/m2 a

0.75

0.003 kg/MJ

0.4 kg/m2 a

The values in the table correspond to those for the Swiss electricity mix, i. e. they stand for MJ primary energy / MJ power consumption for operation of the heat pump.

27 

4.4

Perspective of an investor with a long-term investment horizon

Multi-storey timber building has gained a reputation as an ecological and resource-efficient building variant, which is thoroughly confirmed by the present study. The many buildings which have already been constructed demonstrate timber's great potential and technical

versatility. The interest within the property market is rising, but professional and institutional investors are still hesitant.


44  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.4.1  Timber construction with expected returns of investment Multi-storey timber building has reclaimed urban territory. Without causing a stir, re-entry into the city of Zurich took place some time ago: In 2003, the nonprofit, architecturally modern residential development on ‹Hegianwandweg›, presented in this publication, was built. Four years later, the communal housing estate ‹Wolfswinkel› in the outlying area of Affoltern was constructed: professionals were astonished at the low cost of this residential development. The hybrid timber construction (steel supporting structure and a shell of wood materials) remained largely unnoticed by a broader public, although it is still striking in the urban context. Only now is multi-storey timber construction being discussed publicly, probably not least because examples of it have also arrived in inner city areas. The first seven-storey building in Switzerland was built two years ago in close proximity to the Albisriederplatz in Zurich. The ‹Badenerstrasse› housing complex, with solid wood structural walls, complements the layout of a typical city street. And on one of the best real estate sites of all, right by Zurich Stadelhofen station, a six-storey town house with wood structure and facade will fill the gap in a perimeter block development. And this is far from a complete list of projects, either finished or in the making, that use multi-storey timber construction. Completed projects of this kind – there are now around 1500 – and projects in the planning stage, can be found throughout Switzerland. Moreover, a typical feature is not only an unusually high proportion of wood, but also an innovative property developer and investor base. It is striking that nonprofit and public building owners in particular are keen to discover and try out modern timber construction as a viable alternative to the densification of residential neighbourhoods and urban streets. 4.4.2 Ecological investment motives The history of modern multi-storey wooden building is still young. From the structural engineering, construction and aesthetic perspectives, promising references are already available. But the reason why Zurich’s housing cooperatives, the city of Berne’s property management department, and private land owners prefer timber construction primarily has a very specific project-related reason: the use of available building material in Switzerland is ecologically motivated. To comply with the careful use of finite resources and the 2000-watt society, building concepts should not only be energy efficient, but also use sustainable construction methods. Non-profit investors are also carefully choosing materials for buildings designed to replace older residential estates built with solid construction techniques, where modern standards are no longer met. In addition to individual ideological convictions

there is the intention to meet the needs of future residents more satisfactorily. This is because environmental commitment also has an indirect economic idea behind it. A reduction in extra costs – typical for energy-efficient residential buildings – can significantly increase demand in the current and future real estate market. The supply concept whereby the gross rent should be reduced for new buildings is not only familiar to cooperatives. Institutional investors with initial experience of multi-storey timber building also specifically emphasise the reliable price basis for new tenants. Such an investor is the insurance company Allianz Suisse, which built the zero energy settlement ‹Eulachhof› in Oberwinterthur in a hybrid design – with a solid concrete core and a light building envelope of wood. Increased costs of approximately 10 % were seen as acceptable. Nevertheless, a market rate of return of over 4 % is expected. The second major investor's publicity concentrates less on the numbers than on the creation of high quality building stock through the use of wood as a building material. The real estate department of Credit Suisse has created a smaller residential area in timber construction in St. Erhard in Lucerne. Its arguments include an orientation towards sustainable residential buildings, but even more importantly the choice of healthy and recyclable materials. Investments in the real estate market are currently also driven by demand. People with an urban and environmentally conscious lifestyle are highly impressed by the modern uses to which timber, a traditional material, is being put. 4.4.3 Apartment buildings: a growing trend The construction of multi-family homes is booming. Fortunately, multi-storey timber construction can derive exceptional benefits from this trend. The market figures compiled by the timber SME centre show an increasing market share, which now amounts to about 5 %. In the segment of single-family homes, the market share is almost three times higher, which reflects the fact that timber construction is able to implement energy efficiency demands in contemporary architectural designs. It is therefore not surprising that a survey on the choice of wood as a material, carried out by the Berne University of Applied Sciences, found that private building owners greatly appreciate the functional qualities of this natural building material, and are convinced by timber construction as a modern and ecological variant. In addition, it is becoming apparent that architects’ voices are being heard – in the search for information as well as in the decisionmaking process. In Germany, the initial situation looks similarly promising: sustainable design is in vogue, and the reputation of wood is very good. Its particularly attractive fea-


45 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

tures are good insulation, a healthy and comfortable indoor climate and diverse uses – both functional and aesthetic. The industry is seeking to meet the demand with innovative system solutions. But there is resistance in our northern neighbour, too. The study of the future sponsored by the German Federal Ministry for Research and Education on wood recycling ‹Holzwende 2020 plus› has encountered stubborn prejudices, especially in investors: they believe that timber construction is not long-lasting enough, creates problems with fire and noise protection, and is susceptible to pests. A detailed survey is being prepared for investors in Switzerland, because there are reservations and concerns in this country too. These relate, for example, to uncertainty about the development of life cycle costs, since the existing reference

Figure 33: Life cycle costs. Source: Sustainable property management, KBOB

buildings are only a few years old. The fact that life cycle costs and maintenance are among the most important decision criteria has also been demonstrated in the survey of building owners by the Berne University of Applied Sciences.

Life cycle costs of a building Life cycle costs 80 – 100 years 100 %

Investments 3 – 5 years 0 % 1 year Planning

1 year

 Controllability of costs

1 – 3 years Construction  Less sustainable building

4 x 20 – 25 years Management  More sustainable building

1 year Liquidation


46  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

4.4.4 Optimisation potential Investors in the pioneering timber buildings already constructed also assume that a standardisation and optimisation potential remains untapped. People are aware that the planning process must be geared to wood in the early stages, where the choice of a robust cladding and structure are the most frequently and thoroughly discussed topics. On the other hand, timber is praised not only because of its environmental advantages, but also for positive experiences relating to building hygiene, light design and short construction and installation times. Not least because of these factors, load-bearing timber construction has acquired a good reputation and high market share in flexible office buildings or in the renovation and expansion of multi-family homes. The Zurlinden cooperative also provides a vivid example of how the design and technical know-how

Figure 34: Participants in the real estate process Source: Sustainable property management, KBOB

acquired may be put to profitable use: it has developed a novel, solid wood wall system for the sevenstorey residential development on ‹Badenerstrasse›. In addition, internal noise control – despite the tenants’ own concerns – has been achieved without any complaints to date. The next multi-storied wooden settlement is therefore already under construction. Also in ‹Sihlbogen› the walls and ceilings are made entirely of wood. And because almost all the commissioned craftsmen are cooperative members themselves, they are hoping from a direct competitive advantage from the project.

Roles and aims of participants in the real estate process Strategic level Developer / Short-term investor

Long-term investor

Maximum return on capital invested

Client

Owner

Low costs Flawless building

Regular, satisfactory returns Maintenance / Increase of value Long-term ease of rental Low life cycle costs Image, reputation Fulfils the intended purpose Low risk of changes in the law Low risk of changes in price Low risk of social changes

Portfolio manager

Facility manager

Operational level Construction project organisation

Building manager

Tenant / User

Low maintenance costs Satisfaction User / Owner Trouble-free operation

High quality of life Good services Low additional costs Low occupancy costs / rents


47 Climate-friendly and energy-efficient construction with wood – Basic information and implementation

5 Outlook

The issue of climate-friendly and energy-efficient construction with wood is topical and highly interesting. The results of the studies carried out in the context of this publication confirm the statement of Prof. Dr. Werner Sobek (Stuttgart), that ‹light building is becoming an important prerequisite for sustainability›. Nevertheless, timber construction will not become either a general attitude or an integral solution through one-sided enquiry. In the future, limiting cost management boundaries to the building itself (keywords ‹self-sustenance / costs›, ‹LowEx› ) or even to individual components and products, will continue to lose significance. Besides determined implementation of the principles of light construction and the cascade use of wood, today’s planning and construction techniques must continue to move forward. Currently, blinds or awnings are often the only dynamic component of a building. The recyclability of cars is 90 %, while buildings often reach only 4 %. The timber industry is facing a challenge – clever ideas and projects are needed. To increase the use of wood further, open communication is required, which continues to demonstrate the benefits of wood-based architecture using a broad range of arguments. It is hoped that this ‹Lignatec› will help to underline the strengths of timber construction regarding climate protection and energy efficiency.

Implementation The second part of this ‹Lignatec› covers the implementation of CO2 - and energy-efficient timber buildings at the planning level, with examples of new construction and conversion projects. Like this part, it offers decision-makers arguments and facts, and also provides architects, engineers and planners with practical guidelines for implementation.


48  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

6

The environment is an issue – with good reason

The scientific community largely agrees that most of today’s global warming is caused by people. While the exact impacts of climate change are unclear at the local level, there is enough scientific evidence to show that CO2 emissions from fossil fuels for industry, household and transportation, and from the deforestation of primary forests, are the foremost causes of global warming, and that their overall effects will be mainly negative. The current concentration of CO2 in the atmosphere is 28 % higher than at any time in the past 800 000 years. 27, 28 Swiss federal policy requires CO2 emissions in Switzerland to be reduced by 20 %, compared to the Kyoto reference year of 1990, by 2020. Mainly due to better building envelopes (in redevelopment and new construction), there are positive developments regarding fuel consumption for industry and household, which has diminished by nearly 13 % of the reference year figure. Fuel emissions overall have not decreased compared to 1990, however, because fuel consumption for transportation has increased by the same percentage. Simply achieving an 8 % reduction of the 1990 figure by 2012, already agreed under Kyoto, is a challenge for Switzerland. The fact that the targets are being ap-

proached in the segment of industry and household fuel emissions is no reason for complacency. This partial success is based not least on the rapid introduction of stricter building codes (MuKEn) and steering instruments (CO2 tax) on the one hand, and the swift provision of redevelopment incentives (building programme) on the other. Even more targeted approaches are needed for the construction sector, however. Forests and wood can make a significant contribution to reducing the greenhouse effect. Lignum’s ‹Lignatec› on the theme of climate-friendly and energy-efficient building with wood provides basic information about timber and its specific properties in this ecological context. www.kommunikation.unibe.ch/content/medien/medienmitteilungen/ news/2008/epica

27 

More information can be found , for example, in Boulouchos K. et al. 2008: Energy Strategy for ETH Zürich. ESC Energy Science Center, Eidgenössische Technische Hochschule Zürich

28  

6.1 Forests and wood as pioneers of a more sustainable building stock As shown in the first part of this ‹Lignatec›, wooden structures have a better environmental profile than comparable buildings made of other materials. Overall, it can be said that forests and wood in construction simultaneously create multiple benefits for the climate: timber not only stores carbon (storage effect), but also replaces other more energy-intensively manufactured materials (substitution effect), while CO2 continues to be bound in wood in forests. The best way to use this high quality material is in a cascade, whereby thermal utilisation occurs only after its use as a raw material for products and recycling. As with all renewable resources, however, wood is a biomass that should not be wasted in its use as a energy source, either. This means, for example, that buildings must have an efficient envelope which ensures the lowest possible heat transfer and is airtight. It is also important to pay attention to the energy cascade. Higher-grade energy sources such as electricity must take priority over heating energy and should also be derived from biomass in the first instance. Complex quantity calculation for carbon sequestration Wood consists of about 50 % carbon. At the international governmental level 29 there are efforts to transfer the net growth of the forest as a carbon sink to wood products – mainly with the aim of representing the CO2 balance or ‹carbon footprint› more accurately.

Similarly, the net growth of wood products can also be allocated to newly produced wood products (timber houses, etc.). This enables the carbon sequestration in the wood to be assessed at the design stage and when choosing materials. Besides the more climatefriendly construction of timber buildings compared to other conventional construction methods, some of the emissions are at the same time reduced by carbon sequestration. Timber construction is increasing its market share in Switzerland, especially in multi-storey housing. As the utilisation potential of Swiss forests is still far from being exhausted, the carbon store is increasing both in forests and in buildings made of wood, which has a positive effect on the climate. At the national level, however, it is important to note that only the net changes in the total carbon store - that is, the combination of carbon storage in forests, wood products and buildings – are relevant to the climate (as an increase or decrease). Also in Switzerland

29 


49

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

6.2 CO2-Bank: communication tool for the environmental performance of wood The CO2 -Bank Switzerland makes the climate benefits of the wood used for construction in Switzerland visible. This Internet-based database primarily provides a computational tool that enables measurement of the CO2 reduction of buildings due to the use of wood, once the wood type and wood-based materials have been entered. This performance is shown cumulatively by the CO2 -ton calculation tool. Companies in the timber industry and planners (architectural or engineering firms, timber-construction or joinery companies) can register and have their contribution calculated.

The CO2 -Bank Switzerland is an initiative of the forest and timber industry. Participation is free, non-binding and without obligation. The CO2 -Bank is managed by the Swiss Association for tested quality homes VGQ. Its activities are supported by self-help funds of the Swiss forest and timber industry SHF. 30 30 

Further information can be found on the website of the CO2-Bank Switzerland (www.co2-bank.ch).

Figure 35: Certificate of the CO2-Bank Switzerland

6.3 Assessment of sustainability As described in detail in Section 3.4, various instruments and tools are available to assess the sustainability of a building. In the following sections, three new construction projects and one conversion are used to show how buildings can be assessed according to the SIA booklet 2040 ‹SIA path to energy efficiency› – which is characterized by a total energy approach. The examples provided are each representative of a particular type of building. Not least because the calculations are usually done in comfort at the computer, it is important that plausibility studies are carried out afterwards. This is due to the fact that users have found dangers lurking in the application of these systems which may distort the results significantly. The primary errors occur in the choice of products: a well known example is the choice of only air-dried wood for a wood industry product such as a solid timber construction system. The wood used for such products is also often kiln dried, and it must therefore be selected accordingly and the correct mix calculated. Another example is concrete: it must be ensured that the reinforcement is used realistically or not completely forgotten. Also, one often sees wrong product lives entered in the calculations: the details of the embodied energy and greenhouse gas emissions normally need to be related to a single year and the specified useful lives must be considered. Regarding the KBOB (Coordination Conference of Federal Construction and Properties Services) list, the gross density of the materials also requires examination by an expert. This is because although the primary energy and greenhouse gas emission data are based on the mass in the KBOB list, no gross densities are shown there. To obtain a usable result, therefore, the gross densities must be assumed. This requires an exact approach, since a gross density incorrectly applied can distort the result significantly. It is also important to note the influence one particular figure can have on the system. For example, regarding the impact of the gross density of wood on the environment, a high correlation between

density and environmental factors can be assumed (for the same processing), since weight (internal and some external transport) and resistance during processing (electricity consumption, energy for drying assuming the same moisture content) depend on this property to a large extent. On the other hand, there are also some environmental impacts that do not directly correlate with the density, such as sawing and planing. Even regarding the external transport of timber, it is often not the weight that is decisive, but the volume. Timber construction really does perform much better As in the comparative calculations in the first part of this ‹Lignatec›, the buildings in this section are also completely assessed. This means that, in conformity with the SIA booklet 2040 ‹SIA path to energy efficiency›, the figures calculated and presented include the basement in solid construction, the foundations and even the underground garages. Of course these building components have an enormous influence on the overall result, as can be seen in the tables for the examples in Section 8. Despite this heavy burden, timber buildings show good overall results, even considering the relatively small advantage over other construction types in some areas. If these example buildings used a different construction method, though, they would fail to achieve many of the target values as specified in the SIA booklet 2040 ‹SIA path to energy efficiency›, especially with greenhouse gas emissions. From this perspective, timber construction often has the potential to tip the balance. However, it actually achieves a great deal more. For example, if the underside of the floor slab alone were assessed and compared, or a direct comparison made of building elements using various construction methods, timber construction would demonstrate many more benefits, especially due to its high energy efficiency and low values for embodied energy and greenhouse gas emissions.


50  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

7

Background and concept of climate-friendly buildings

7.1 The 2000-watt society as a goal As explained in Chapter 6, in the face of ongoing global warming the Swiss Federal Council and Parliament are seeking, in the pending revision of the CO2 Act, to achieve a 20 % reduction of greenhouse gas emissions, compared to 1990 levels, by 2020. The Swiss Society of Engineers and Architects (SIA), and with it the city of Zurich, for example, is going even further in this respect: by 2050 the population of Switzerland should consume two-thirds less energy than today and emissions of greenhouse gases should even be reduced to a quarter of the current amount. The SIA booklet 2040 ‹SIA path to energy efficiency› and the associated documentation D0236 form the basis for implementing this strategic milestone for the 2000-watt society in the building sector by 2050. The contribution of the building sector to achieving these goals should not be under-

7.2

estimated: the construction, maintenance and operation of buildings accounts for about half of the total energy consumption and also nearly half of all greenhouse gas emissions in Switzerland. 31 The SIA booklet 2040 ‹SIA path to energy efficiency› anticipates that the building sector will continue to be responsible for about half of Switzerland's energy consumption and greenhouse gas emissions. Thus, if the right measures are taken in the construction and operation of buildings, this will be a very important step in the right direction. On the other hand, if the turnaround in the building sector does not succeed, the 2000-watt society will remain a utopia. Federal Office for Energy SFOE, ‹Swiss overall energy statistics 2005›, www.admin.ch/bfe

31 

Energy and greenhouse gas emissions

The SIA booklet 2040 ‹SIA path to energy efficiency› is characterized by a total energy perspective: in addition to the energy required for building operation, embodied energy and location-dependent mobility are taken into account. An important innovation, compared to previous documentation, is that the booklet also specifies targets for greenhouse gas emissions. These are a vital factor for the environment and are at least as important, if not more so, than non-renewable primary energy. If the milestone of the 2000-watt society for the year 2050 is to be achieved in the building sector, then the target values for energy and for greenhouse gas emissions will need to be taken into account. The new SIA instrument applies not only to new buildings but also to alterations and renovations. The target values are the sum of energy consumption as well as the emissions from the three key areas of construction, operation and mobility. Compliance with target values is the only requirement in the efficiency path: trade-offs between the three areas are allowed. The way to achieve these target values remains completely open. This permits the consideration of project-specific conditions and leads to innovative solutions. Buildings already constructed according to the target values of the SIA booklet 2040 ‹SIA path to energy efficiency› also show that planners are given more rather than less scope when the areas of construction and mobility are considered in addition to operating energy. 7.2.1  Embodied energy / non-renewable primary energy The term ‹embodied energy› is reserved exclusively for the area of ‹construction›. In the areas of ‹operation› and ‹mobility› the term ‹non-renewable primary energy› is used. But ‹embodied energy› is also ‹non-renewable primary energy› (cf. Section 7.3, Construction).

In this ‹Lignatec› ‹embodied energy› is consistently used for the ‹construction› area, because it is a common term. In the areas of ‹operation› and ‹mobility›, the term ‹non-renewable primary energy› is consistently used. 7.2.2 Amortisation All the products in a building have an amortisation period, which is calculated in the SIA booklet 2032 ‹Embodied energy of buildings›. 32 The embodied energy and the greenhouse gas emissions of building components etc. are usually calculated for the corresponding amortisation period. If not explicitly stated, all figures in this ‹Lignatec› are amortised values and thus correspond to one year. The determination of amortisation times in this booklet is based on various tables for life and use periods. Nevertheless, the SIA 2032 Commission purposely did not make the amortisation periods shown in Appendix C the same as the use periods. In building components with shorter lives it is true that the amortisation period approximately corresponds to the use period. But shorter amortisation periods are used for the load-bearing structure, to prevent future generations from being unduly burdened by the depreciation of today’s investments.

32 


51

Figure 36: The timber product cycle in the construction area

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

7.2.3 Target values The construction area Embodied energy comprises the cumulated energy consumption for the production of building materials, the construction of buildings, any replacement investments and the disposal of the building. In the same way, the greenhouse gas emissions are cumulated over this building life cycle. Embodied energy is primary energy, and is also in fact non-renewable primary energy. The definition and calculation methodology for embodied energy is given in the SIA booklet 2032 ‹Embodied energy of buildings›. The embodied energy and greenhouse gas emissions can be related to the building component surface. In the SIA booklet 2040 ‹SIA path to energy efficiency› the energy consumption and greenhouse gas emissions of a building are calculated, based on the energy reference area of the building, and are then converted to annual values using the amortisation times allocated to individual building components.

Figure 37: The operation area comprises room heating, hot water, ventilation / air conditioning, lighting and operating equipment.

The operation area The operation of buildings comprises all energy consumption for space heating, hot water, ventilation / air conditioning, lighting and operating equipment. These categories of energy consumption are included in final energy. In the SIA booklet 2040 ‹SIA path to energy efficiency› they are converted by means of primary energy factors and the greenhouse gas emission coefficients of the respective energy sources into non-renewable primary energy and greenhouse gas emissions. Here too, the reference value is always the energy reference area of the building.

Figure 38: The mobility area comprises everyday mobility and the infrastructure (vehicles, roads, railways etc.).

The mobility area Mobility comprises the everyday movement of people and the corresponding infrastructure (vehicles, roads, railways etc.), based on a building’s location. Depending on where the building is located (in a dense urban core or in a more rural area) and how well the location is served by public transport, 33 the occupants of the building will need to cover more or less long distances and do so with different means of transport. The energy consumption for mobility as a function of the building location is defined in the SIA booklet 2039 ‹Mobility – energy consumption depending on a building's location›, where the calculation methodology is also described. In the SIA booklet 2040 ‹SIA path to energy efficiency›, location-based mobility is defined in terms of primary non-renewable energy and greenhouse gas emissions and related to the energy reference area of the target building. Public transportation quality classes according to http://map.are.admin.ch

33 


52  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

7.3

The three areas of operation, construction and mobility

7.3.1 Important factors in operation Energy efficiency in operation is a well-established and familiar demand, thanks to the Minergie labels, the energy performance certificate of the cantons (GEAK) and also statutory requirements. The recipes required to reduce energy consumption and emissions during operation are well known: a correctly designed building envelope with good insulation and high solar gains reduces heat demand, while energy-efficient appliances and lighting systems lower power requirements. The remaining requirements are largely met by renewable energy sources. 7.3.2 Important factors in construction Energy and resource efficiency in the construction or renovation of buildings, however, has only been recognised in recent years. As described in detail in Section 3.5, the figures for embodied energy and greenhouse gas emissions take into account the cumulated expenditure of non-renewable primary energy for the production and disposal of building materials. All upstream processes – from raw material extraction through transportation, manufacturing and processing – as well as the downstream processes such as waste disposal – are included. The same applies to greenhouse gas emissions. In the area of construction, the relevant control variables needed to reduce energy consumption and emissions are still not well known: large and compact structures which require a low building envelope area in relation to the generated surface area provide an excellent foundation. Simple structural systems with linear load deflection and reasonable spans reduce the cost of materials. Especially in terms of greenhouse gas emissions, the choice of design can also influence the result: timber construction benefits from relatively low construction energy expenditure and short transport distances, especially if the building materials are locally produced. Wooden structures are usually lighter than solid construction – a simple rule of thumb is that light structures perform better than conventional heavy systems (cf. Section 4.3.3). 34 However, to ensure that the positive characteristics of wood as a building material are not decimated in multi-storey construction, the relevant parameters need to be thoroughly considered in the planning stage: large spans and increased requirements for sound insulation and fire protection often lead to additional, resource-intensive layers in multistorey buildings, which need to be optimised by clever solutions and concepts. Under certain circumstances, mixed construction may prove more advantageous.

7.3.3 Influence of the building location The third area in the SIA booklet 2040 ‹SIA path to energy efficiency›, location-related energy consumption for mobility, is probably the least known. In this area, the energy that is used for transportation is considered as well as the greenhouse gases emitted by vehicles. Mobility also includes the embodied energy and greenhouse gas emissions generated by the production of vehicles, as well as the provision of the infrastructure for traffic. 35 In the SIA booklet 2040 ‹SIA path to energy efficiency› only the portion of mobility which can be directly assigned to the location of a building is considered. Mobility highlights the striking correlation between the location of a building and the mobility behaviour of the building users. The largest ‹adjusting screw› in mobility is therefore the choice of location: the project values for mobility are largely predetermined by this consideration. Location factors which can be selected in the calculation aid 36 for the SIA booklet 2041 ‹SIA path to energy efficiency› are not usually mutually independent: a building in a city core usually benefits from a well-developed public transport network, local shopping facilities and parking regulations which allow fewer parking places compared to more remote locations. All of these result in a positive influence on mobility. Lightweight materials / construction types may have a significantly less favourable sustainability profile than heavy ones, for example aluminium lightweight construction as opposed to rammed clay.

34  

Methodological basic information according to SIA booklet 2039 ‹Mobility – energy consumption according to building location›

35 

‹SIA-Tool 2040 Effizienzpfad Energie› (‹SIA-tool for the SIA 2040 path to energy efficiency›): http://www.energytools.ch

36 


53

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

7.4 Special features of the planning process In principle, the same principles apply to the planning of buildings which are intended to reach the targets of the SIA booklet 2040 ‹SIA path to energy efficiency› as are required for any well-run planning process. The most important decisions are already made in the preliminary study and pre-project phases. The first steps in the design process are especially critical for the area of construction. The shape, size and compactness of the building, the internal organization of space and the resulting support structure are determined in these early stages of the construction process. The opportunity to exert influence in the later phases is significantly smaller. Experience shows that a successful construction process succeeds best when it is characterized by several important features: A clear commitment is required on the part of the building owner or investor that the construction should be carried out in accordance with the SIA booklet 2040 ‹SIA path to energy efficiency› or the goals of the 2000-watt society. This commitment serves as a guiding principle for important decisions and sets an agenda for all participants in the construction process. Not every project is suitable for implementing the corresponding guidelines. Often the location sets strict limitations. A feasibility study is the basis for an initial trial calculation using the computational tool ‹SIA-tool for the SIA 2040 path to energy efficiency›. This simple tool provides users with a reasonably

reliable indication in the earliest planning phase of the chances of the project’s success. The requirements of the SIA booklet 2040 ‹SIA path to energy efficiency› must be co-determinant in the selection of a project. This input must take place in the pre-project phase, in the case of competitions in the form of the programme and for direct orders as part of the project requirements specification. Interdisciplinary expertise is a prerequisite for success. This particularly applies to the first design steps. What is required is a team, not lone fighters. The entire life cycle is relevant for the evaluation of a project. This takes into account construction, operation, renovation, repair and demolition. Quality assurance throughout all phases of planning and implementation checks the achievement of objectives at important milestones and guides and motivates participants.

7.5 The term ‹sustainability› Green building, sustainable construction, energy-efficient construction – the names are many, and the terms are often used carelessly as synonyms. This does not do justice to the cause. But making a clear distinction is not so simple, because the meaning of the terms becomes more complex as they increase in popularity. The concept of sustainability has probably suffered most. Anyone looking through the media today will meet the word ‹sustainable› so often that they may well end up wondering whether the word actually still has a defined meaning at all. ‹Sustainable development› today is probably still best captured by the threecircle model 37, which was developed on the basis of the Conference of Rio 38: sustainable development according to this model aims at a thrifty use of resources (environment), a cohesive society and economic wellbeing. All three circles – environmental, social and economic – must be taken into account; they relate to each other and overlap to a large extent. The Federal Office for Spatial Development ARE 39 describes this connection as follows: ‹Economic well-being, like the preservation of natural resources, is the precondition for the

satisfaction of our material and non-material needs. And only a caring society is able to distribute consumer goods fairly, maintain social values and handle natural resources thriftily.› Apart from the three circle model, the ‹three pillar model› and the ‹triple bottom line approach› or ‹triple bottom line› are current terms.

37 

United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, 1992

38 

Federal Office for Spatial Development, Berne, the federal government’s coordination platform for sustainable development policy in Switzerland, www.are.admin.ch

39  


54  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 39: Sustainable development considers criteria from the environment, society and business equally. It takes a long-term, global perspective and explores the implications of our actions today on future generations.

Rio three circle model

North

Economic well-being Caring society

Society

Efficient use of resources

Today’s generation

Tomorrow’s generation

Environment

North – South Today – Tomorrow

Economy

South

The term ‹ecology› belongs in the environmental circle. Ecology aims at comprehensive environmental protection. Because man is also part of the ecosystem, ecology also plays a key role in the social circle. This mainly affects individual needs, such as those for

7.6

sufficient and healthy food, air and water, or for an environment that is conducive to healthy human development.

The SIA booklet 2040 ‹SIA path to energy efficiency› in context

Since nothing happens in the world without energy, and climate changes resulting from greenhouse gas emissions could lead to a partial or even greater collapse of the world economy and of many social and political structures, the SIA booklet 2040 ‹SIA path to energy efficiency› addresses the issues which are a vital prerequisite for sustainable development: In the environment circle of the three-circle model of sustainable development, it comprehensively addresses the thrifty use of our most important resource, energy. The second circle, the social dimension of sustainability, is only marginally dealt with by the SIA instrument: quality of use, social, spatial and architectural value or the quality of indoor air and other healthrelated aspects cannot be expressed through energy and greenhouse gas emission figures. An optimal management of resources in the construction of buildings leads to simple, compact and well organized structures with high flexibility. Thereby a good foundation is also laid in the third circle of the sustainable development triad, which deals with the economy. These measures, com-

bined with regional value creation and resource use, lead to high-quality, low-cost buildings in both construction and operation. This total-energy approach that includes embodied energy and mobility, and in particular the formulation of targets for greenhouse gas emissions, is unique to the SIA booklet 2040 ‹SIA path to energy efficiency›, not only for Switzerland, but also for neighbouring countries. The total energy approach, taking into consideration climate-relevant greenhouse gas emissions, will prevail in the future and replace one-sided operating energy perspectives.


55

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8  Implementation of climate-friendly buildings in accordance with the SIA booklet 2040 ‹SIA path to energy efficiency› Example of the residential / new construction category of buildings Figure 40: The garden city estate ‹Grünmatt› with loggia and external walls in timber frame construction with rear-ventilated wood cladding. Visualisation: architron, Zurich

8.1 The Grünmatt estate – timber construction makes it possible Urban development / neighbourhood The Friesenberg district in Zurich is located at the foot of the Üetliberg and mainly comprises groups of terraced houses with a comfortable distance between them. The Family Home Association Zurich (FGZ) rents approximately 2200 residential properties in this quarter. 155 residential units are to be built on the ‹Grünmatt›- and Baumhaldenstrasse. The project, implemented by the architects Graber Pulver, replaces 64 single-family homes dating from 1929, which are in a poor condition, no longer meet today’s energy requirements and also no longer correspond to current needs regarding living quality and comfort. Project The project emerged from a study contract. The FGZ expected ‹a pioneering interpretation based on a garden city› and explicitly required plenty of public and private outdoor space. Graber Pulver Architects have arranged thirteen buildings in four slightly curved rows, which is strongly reminiscent of the former terraced houses. The project was praised in the jury report as an ‹innovative further development of ‹Zeilenbau› and terraced housing›. No specific guidelines for energy were formulated in the study contract. Building 4, located in the southwest of the parcel of land, is considered here. This is a four storey building with four apartments per floor, which are accessed via two staircases. A striking feature of the floor plans is the fact that the living area extends over the entire

depth of the building. It has a generously proportioned private loggia in front of it, always in the south and therefore facing the hillside. A gently sloping pent roof opens towards the sunny side. Some individual rooms and all the auxiliary rooms of the apartments are located in the basement. The parking facilities are a large shared garage for all 13 buildings, located between the top two rows. For calculation purposes 10 % of the garage is allocated to Building 4. This corresponds to this building’s proportional share of the estate’s total floor area. The energy concept of the FGZ estates on Friesenberg is in transition. Until mid-2012, the heating demand of the FGZ settlements will continue to be covered by an oil heating system. The cooperative may in future replace this heating arrangement by using waste heat from surrounding large firms, combined with local heat pumps. The ‹Grünmatt› estate is the first FGZ estate to be connected to this readily available and so far little used source of heat. In this way it is the pioneer for the expansion of the energy network in Friesenberg.


56  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.1.1 Construction, operation and mobility Construction The estate’s relatively small and compact volume is a poor precondition for limited quantities of embodied energy and low greenhouse gas emissions. Nevertheless the results in these areas are remarkable, thanks to the compact building shape with its projecting balcony layer, and to the timber construction chosen. The part of the building above ground is executed in timber construction, except for the staircases, and rests on a basement in solid construction, built into the hillside. A wood-concrete-composite floor system is used for the ceiling structure. The solid timber used for the ceiling soffit remains visible, so that elaborate cladding is unnecessary. Façades and walls in a simple timber frame construction are prefabricated in the factory and

Figure 41: Cross-section through the façade

can be transported even in large element sizes, thanks to reinforced OSB panels. The façades are clad in alternating horizontal and vertical timber boarding. A major challenge of this construction site is coordinating the solid construction work (basements, stairwells and the front façades made of concrete slabs) with the incomparably more precise timber construction: the houses are measured up to the nearest millimetre and the elements are produced accordingly.

Roof: Substrate 100 mm Flexible sheets for waterproofing Insulation 200 mm Vapour barrier OSB 15 mm Solid timber 160 mm

Ceiling above ground floor: Covering 10 mm Cement screed 80 mm Footfall sound insulation 2 x 20 mm Wood-concrete-composite floor

Reinforced concrete 100 – 120 mm

Solid timber 100 – 120 mm

Exterior wall: Plasterboard 15 mm OSB 15 mm, with taped and sealed joints Stud 280 mm / Insulation Breathable, medium density wood fibreboard 15 mm Home wrap Battens 40 mm Wooden façade 20 mm

ekcednegaragfeiT na ssulhcsnA

ekcednegaragfeiT na ssulhcsnA

ekcednegaragfeiT na ssulhcsnA


57

Operation The house achieves outstanding U-values through a mineral wool insulation of 280 mm on the façades and 200 mm EPS insulation on the roofs: 0.14 and 0.12 W/m2K. With this well-insulated building envelope, a low heating demand would be expected. However, the orientation of the buildings with the south side facing the Uetliberg leads to only small solar gains. The heating demand remains just 15 % below the legal requirement. The whole quarter of the FGZ will be successively supplied from the summer of 2012 by a closed circular

Figure 42: The waste heat from the surrounding large companies will be fed into a circular pipeline and used directly or, especially in the summer, stored in underground storage tanks. In the colder months the stored heat can be retrieved. Source: Amstein + Walthert AG

Planned heat supply to the FGZ

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

pipeline transporting waste heat from large companies in the surroundings. In summer their excess heat will be stored in underground storage tanks. In the colder seasons this will be raised locally to the required temperature by heat pumps. Photovoltaic panels on the roofs of the settlement will cover part of the electricity demand. The necessary exchange of air in the apartments will be ensured by air boxes in the outer walls, which will supply air to the apartments, while the exhaust air will be centrally extracted into the wet rooms.


58  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Mobility The ‹Grünmatt› estate is being constructed in the city core of Zurich and is very well connected by public transport. There are shops in easy walking distance. These are good conditions for energy-efficient mobility behaviour on the part of the estate’s residents. One drawback is the large number of parking spaces that need to be created on the site: although the FGZ is constructing the minimum number of parking spaces in accordance with applicable parking regulations,

Figure 43: Location of the ‹Grünmatt› estate in the city core of Zurich. Public transportation is quality class A, according to http://map.are.admin.ch

Footnotes for Figure 44, page 59.

this yields 0.85 parking spaces per apartment. The large-scale underground garage is not only costly and resource-intensive to construct, but experience shows that large parking spaces also lead to more vehicle owners. In the city of Zurich only 42 % of households own a car, thanks to the very well-developed public transport system. The FGZ therefore assumes that not all parking spaces will be rented.

Location Grünmatt-, Baumhaldenstrasse, Zürich Client FGZ Familienheim-Genossenschaft Zürich Architecture Graber Pulver Architekten AG, Zürich Construction management Perolini Baumanagement AG, Zürich Civil engineers Freihofer & Partner, Zürich Timber construction engineer Pirmin Jung Ingenieure for Holzbau AG, Rain Building services Advens AG, Zürich und Amstein + Walthert AG, Zürich Timber construction ARGE Blumer-Lehmann AG, Gossau, und Kost Holzbau AG, Küssnacht am Rigi Construction costs BKP 2 CHF 62.45 million (entire project including underground car park) of which BKP 214 CHF 11.14 million (entire project including underground car park) Total property area SIA 416 31799 m2 (entire project including underground car park) Floor area SIA 416 32574 m2 (entire project including underground car park), 27400 m2 (entire project), 1980 m2 Energy reference area SIA 416/1 1667 m2 (Building 4) Building volume SIA 416 102 919 m3 (entire project including underground car park), 84642 m3 (entire project), 5990 m3 (Building 4) Building envelope Figure SIA 416/1 1.29 (Building 4) Compactness (entire building envelope in proportion to floor area) 1.40 Cubic metre price SIA 416 (BKP2) CHF 607.– Construction period Building 4 2010 – 2012, entire estate by 2014

Embodied energy is measured according to kWp. Electrical auxiliary energy for space heating and hot water; for heat pumps it is already included. 42  The requirement for circulation in the energy network is estimated here. 43  Where the electricity requirement of the ventilation is stated in a Minergie certificate, these figures can be used in the first phase. 44  The electricity requirement of the air box system is estimated here; it is somewhat better than a fully developed ventilation system with heat recovery, as specified in the booklet SIA 2040 ‹SIA path to energy efficiency›, with a pre-project standard value of 6 MJ/m2. 45  For photovoltaics, the expected annual yield is used. But only if a building is also directly supplied and this renewable electricity is not resold, for example, through a cost-covering feed-in tariff (KEV). Otherwise it would be counted twice, because another household could buy this electricity. Periods during the day when excess solar electricity is fed into the network, or when electricity is obtained in return, are regarded as a zero sum game. 46  Visitors’ parking spaces do not need to be included in the calculation. 40  41 


59

Figure 44: The system boundary is the entire building plus a share of the the underground parking. This is 10 % of the entire underground parking and is thus proportional to the floor area of Building 4 related to the entire floor area of the ‹Grünmatt› estate.

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.1.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› Calculation of the non-renewable primary energy and greenhouse gas emissions of Building 4

Construction Underground garage share (10 %) Building under ground Exterior walls

Non-renewable

Greenhouse

primary energy

gas emissions

[MJ/m2]

[kg/m2]

330 m2 floor slab, 330 m2 roof under ground

11

0.9

480 m2 floor slab, 230 m2 insulated concrete wall 780 m2 timber frame construction, wood boarding 175 m2 concrete panels, internal thermal insulation 314 m2 triple glazing wood and metal windows, 366 m2 balconies 990 m2 wood-concrete-composite floors 495 m2 concrete ceilings 1310 m2 interior walls (concrete, light construction, wood) 490 m2 sloping solid timber (Brettstapel), flat roof superstructure 1480 m2 floor covering with underfloor, 700 m2 plasterwork Environmental energy network, ground-source heat pump, electrical, plumbing, ventilation Photovoltaic 24 kWp installed capacity on the roof 40

13 6 2 19 5 3 5 19 17 23

1.1 0.3 0.2 1.4 0.4 0.3 0.4 1.1 1.2 1.5

14 137 110

0.9 9.7 8.5

66 63 5 11 32 66 –163 80 200

1.0 1.0 0.1 0.2 0.5 1.0 –2.6 1.2 2.5

Total for mobility Reference value for mobility

107 130

5.5 5.5

Overall result Project value Target value for residential / new construction

324 440

16.4 16.5

Windows, balconies Ceilings, interior walls

Roof Interior completion Building services

Own production Total for construction Reference value for construction

εSPF [–] Operation Thermal heat Q h = 101 MJ/m2, Waste heat / heat pump 4.0 2.1 Hot water Qw = 50 MJ/m2, Waste heat / heat pump 41 Auxiliary energy  Environmental energy network waste heat 42 Ventilation 43 Simple supply and exhaust air system 44 Standard value for pre-project according to SIA 2040 Lighting Standard value for pre-project according to SIA 2040 Operating equipment Own production 240 m2 photovoltaic installation on the roof 45 Total for operation Reference value for operation

Mobility  Estate type Building location

Endenergie [MJ/m2]

25 24 2 4 12 25 –62

Korrekturfaktor

City core Very well connected: public transport quality class A Season ticket availability Swiss average

0.25

Car availability

0.65

Swiss average

Approx. 132 parking spaces for Parking spaces per 155 households household 46 Distance to shops in km Coop, Schweighofstrasse

1.0 5.0

0.85 0.3


60  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Building 4 of the ‹Grünmatt› estate meets both target values according to the SIA booklet 2040 ‹SIA path to energy efficiency› – extremely comfortably in terms of non-renewable primary energy and by a narrow margin in terms of greenhouse gas emissions. This situation is typical for new buildings. The reduction target relative to today’s figures is significantly stricter for greenhouse gas emissions, with a factor of 4, than the target for primary energy, with a reduction factor of 3. The ‹Grünmatt› estate benefits from its good location in terms of mobility. The guidelines in this area are met without the need for further measures, even with the large number of parking places. With regard to operation, the combi- nation of waste heat recovery with heat pumps and coverage of the resulting electricity needs by the photovoltaic electricity produced on the roof is efficient: the project values in operation are significantly lower than the indicative values. The high annual heating requirement of 101 MJ/m2 is due in part to the small heated volume with the unfa- vourable building envelope figure (thermal building envelope area to energy reference area) of 1.29. On the other hand, the ventilation system chosen does little to lower the energy demand: it does have heat recovery from exhaust air, but this is allocated to the hot water supply, so that the overall energy demand is only reduced slightly, due to the significantly higher temperatures required for hot water. For construction, the values are well above the recommended limits. This is again mainly due to the small volume of the house in question, with a compactness (entire building envelope including underground parking share in pro- portion to the floor area) of 1.40. To make matters worse, only 72 % of the total floor area of 2260 m2 to be constructed (including underground portion) can be used as a heated area. The unfavourable ratio between floor area and energy reference area has a negative effect, because the latter is the basis for all calculations. However, the choice of design has proven to be apt and correct. Decisive savings will be made in greenhouse gas emissions, in particular due to the timber construction method. With four floors, Building 4 in the ‹Grünmatt› estate is the largest building type in the four-row complex. It thus has the best opportunity to achieve the objectives.

In spite of the compact building form with protruding balconies and resource-saving timber, the smaller types of houses on the site will probably not reach the target values. They are starting in an extremely difficult situation: small volumes always show a poor relationship between building envelope area and floor area. In the first stages of the design process much can be achieved with little effort. Turning things around later is not easy, because the largest impact potential has already been allocated. Clear guidelines for sustainable building and energy efficiency were lacking in the study contract for the ‹Grünmatt› estate – and energy efficiency was correspondingly not a criterion in the selection process. In the project planning stage, significant expenditures were necessary to achieve good positioning in the area of energy efficiency after the event. The fact that the largest building types within the community count as 2000-watt-compatible according to the SIA booklet 2040 ‹SIA path to energy efficiency› is – considering the difficult starting situation – a great success.


61

8.1.3 Excursus: ceilings The wood-concrete-composite floors, visible from below, have proven to be a good solution in this building. Surprising as it may seem, the savings in embodied energy and greenhouse gas emissions from using simple cladding for a timber building can be seen when only

Figure 45: Embodied energy and greenhouse gas emissions of four bare intermediate floors (manufacture and disposal, not amortised), calculated with Grisli 47

a square metre of this building component is considered. As a comparison, classic concrete ceilings, woodconcrete-composite floors with and without cladding and a hollow box floor with cladding are set against each other:

Comparison of four typical ceiling constructions for multi-floor timber construction

Concrete ceiling CEM II 300 kg/m3, reinforcement 90 kg/m3, underside with ceiling plaster, painted, total strength 240 mm

762

Greenhouse gas emissions [kg/m2] 75.9

Wood-concrete-composite floor Solid timber (Brettstapel) 130 mm, concrete 90 mm, reinforcement 2.7 kg/m2, underside painted, total strength 220 mm

494

40.4

Wood-concrete-composite floor Solid timber (Brettstapel) 130 mm, concrete 90 mm, reinforcement 2.7 kg/m2, flexible suspended ceiling plasterboard 15 mm, plastered and painted, total strength 260 mm

606

47.6

Hollow box floor with ballast Panelling with triple layer panels 27 mm, cavity damping / ballast 80 kg/m2, flexible suspended ceiling plasterboard 15 mm, plastered and painted, total strength 300 mm

550

32.8

Embodied energy [MJ/m2]

Bare ceilings are normally supplemented by a floor structure with sound insulation and screed. To maintain a

Figure 46: Embodied energy and greenhouse gas emissions of a typical floor structure (manufacture and disposal, not amortised), calculated with Grisli 

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

roughly similar order of magnitude for all the ceilings, figure 46 shows a typical floor structure:

Typical floor structure in multi-floor timber buildings Floor structure (identical for all four ceilings) Soundproof insulation 40 mm, underlay 70 mm, parquet floor covering 10 mm

493 MJ/m2

35.3 kg/m2


62  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 47: Embodied energy in MJ related to m2 building component surface of four bare ceiling constructions (manufacture and disposal, not amortised), calculated with Grisli 

Comparison of embodied energy from four ceiling constructions 800 700 600 500 400 300 200 100 0 Wood-concrete-composite Wood-concrete-composite Hollow box floor with Concrete ceiling floor floor with suspended plaster suspended plaster board ceiling 15 mm board ceiling 15 mm

Figure 48: Greenhouse gas emissions in kg related to m2 building component surface of four bare ceiling constructions (manufacture and disposal, not amortised), calculated with Grisli 

Comparison of greenhouse gas emissions of four ceiling constructions 70 60 50 40 30 20 10 0 Wood-concrete-composite Wood-concrete-composite Hollow box floor with Concrete ceiling floor floor with suspended plaster suspended plaster board ceiling 15 mm board ceiling 15 mm

Omitting cladding decreases the figure for greenhouse gas emissions for wood-concrete-composite floors by around 15 %. However, this seemingly simple measure in the construction process requires additional expense, as the example of ‹Grünmatt› shows. The underside of the solid timber (Brettstapel) must be planed clean, so that no rough areas disturb the smooth impression of the ceiling. All ceiling panels are therefore checked again before transport to the site and reworked if necessary. In the ‹Grünmatt› estate the ceilings are varnished white. In the period up to painting the rooms must be carefully darkened to prevent discoloration due to direct sunlight on the wood. The differences in the values of the different ceiling constructions in this comparison are quite large. This should not obscure the fact that the ceiling construction accounts for only 3 – 7 % of the embodied energy and greenhouse gas emissions for the entire building. It should also be remembered that the values are, in accordance with the SIA booklet 2040, related to the entire energy reference area and amortised, i.e. divided by the respective amortisation period of the structures. Internal claddings like those shown for ceilings are assigned an amortisation period of 30 years in the SIA booklet 2032 ‹Embodied energy of buildings›, whereas supporting roof structures are given 60 years. It is therefore expected that ceiling claddings will be

replaced once during the useful life of supporting roof structures. ‹Grünmatt› also provides an example of how different project-specific framework conditions influence the overall result. The large underground garage which is being constructed on the ‹Grünmatt› estate places a heavy burden on the area of construction: it is responsible for around 10 % of the total embodied energy and greenhouse gas emissions. The environmental audit is also negatively influenced by the relatively high number of parking places. In order to achieve the target values nonetheless, compensation has to be made in other areas. The choice of wood-concrete-composite floors makes a significant contribution in this respect. Related to the structural component it amounts to a reduction of nearly 40 % compared to a concrete floor. Thanks to the woodconcrete-composite floors the embodied energy in the area of ‹construction› for the entire building is 1 % lower after all, and the figure for greenhouse gas emissions around 3 % lower. This improvement against a traditional concrete floor seems to be small. Nevertheless, the fact that such marginal changes can sometimes be crucial is shown by the selected example: Building 4 of the ‹Grünmatt› estate would miss the greenhouse gas emission target if concrete floors were used. Grisli, tool for calculating the embodied energy and greenhouse gas emissions of entire buildings or building components: www.grisli.net

47 


63

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.2 Multiple-family house Segantinistrasse, Zurich – conversion beats new construction Example of the building category residential / conversion Figure 49: The renovated multi-family house on the Segantinistrasse in Zurich with the addition of a floor in timber element construction. Photo: kämpfen für architektur ag

Urban development / neighbourhood The building, dating from 1954, could be anywhere in Switzerland: buildings of a similar type can be found throughout the country in very large numbers and in different urban environments. The building on the ‹Segantinistrasse›, renovated by kämpfen für architektur ag, is in one of the best locations in the city of Zurich, benefitting from a tranquil setting and beautiful views due to its hillside situation on the Hönggerberg. Project The multi-family house from the post-war period was no longer sufficient for the needs of the residents. The basic structure of the building is in good condition, however. With an eye to the careful use of resources, the private owners decided on conversion and the addition of a floor instead of demolition and a replacement building. The redevelopment has expanded the living area, enlarged the window surface and thus decisively increased the living quality. Although the intervention is extensive and the building reaches the maximum volume for a replacement new construction through the addition of the penthouse floor, the conversion remains more economical than a completely new building, due to the preservation of the basic building structure. Nevertheless, such a radical conversion can only be financed by a significant appreciation in value. The rental income from the new 100 m2 penthouse accounts for a disproportionately large part of the construction costs, so that the existing apartments can be relieved financially. But these also benefit from more

living space: three of the five existing apartments have been expanded by an additional 8 m2, while all of them will receive a more generous window area and private outdoor spaces. The quality of living in this multi-family house thereby equals that of new housing. The overall impression of the building after renovation is no longer reminiscent of typical features of post-war architecture. Rather, it is quite surprising to recognise some details that reveal the 50-year-old building structure behind the up-to-date architecture. The three-storey building was originally constructed in the solid design usual in its day. A prefabricated, 250 mm thick timber construction with a plaster exterior was added on top of the existing masonry, to reduce energy consumption. Where there were previously balconies, the living area was expanded. New, spacious balconies were added in front of the façade in a self-supporting steel-concrete construction. The original gable roof, designed as a cold roof, was demolished and replaced by a new storey in prefabricated wood element construction. The energy concept of the building is based on a low heating demand thanks to very well-insulated building envelope and renewable energy sources. The sun provides not only thermal heat for hot water, but also covers a large part of the house’s electricity needs – thanks to the photovoltaic system installed on the roof.


64  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.2.1 Construction, operation and mobility Construction The original structure of the apartment building has been retained in its entirety. The building envelope has been totally newly clad, however: prefabricated timber elements have been attached to the solid, plastered masonry of the existing façade. They contain not only insulation, but also supply air ducts for controlled ventilation and fabric blinds for summer heat protection. The existing top floor was demolished and a new timber construction added. The walls and roof of the new attic apartment were constructed from prefabricated timber elements. The reason why timber was selected is obvious: buildings from the postwar

Figure 50: Connection of the upgraded exterior wall to the intermediate ceiling

period usually have hardly any static reserves; thanks to the timber, the existing ceiling does not have to carry a heavier load then before. In addition, the walls of the new penthouse are exactly aligned above the existing walls of the underlying floors, which allows linear load transmission. The added floor is extremely well insulated with 320 mm mineral wool.

Structure of exterior wall, from inside: Interior plaster 10 mm Brick 120 mm Exterior plaster 20 mm Cellulose fibre 20 mm Studs 180 mm/cellulose fibre thermal insulation Wood fibreboard 40 mm Exterior plaster 10 mm U-value = 0.18 W/m2K

Ceiling structure from above: Floor covering 10 mm Cement underlay 50 mm Footfall sound insulation 30 mm Concrete (existing) 160 mm Against unheated surfaces: Thermal insulation 200 mm Rendering 10 mm


65

Operation Through the insulation of the building envelope, the new windows and the elimination of various thermal bridges, the heating demand of the existing building can be lowered from about 290 MJ/m2 to about 59 MJ/m2 per year. The newly renovated and clad masonry achieves a U value of 0.18 W/m2K, the outer wall of the new top floor an impressive 0.12 W/m2K; despite the disruptions to the outer wall caused by the air ducts inserted. The heat is produced by a ground-

Figure 51: Photovoltaic panels on the roof of the penthouse floor Photo: kämpfen für architektur ag

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

source heat pump. Solar collectors and a photovoltaic system tap solar energy. In energy terms, the converted building achieves the Minergie-P standard and has been assessed as a zero-energy building.


66  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Mobility The location of the building in the city of Zurich is well served by public transport grade B, and yet it is situated in a quiet environment, with a local recreational area on the nearby Hönggerberg. Only a few parking spaces are available for the six apartments.

Figure 52: Location of the ‹Segantinistrasse› property in the city of Zurich. Public transportation is quality class B according to http://map.are.admin.ch

Footnotes for Figure 53, page 67.

Location Segantinistrasse 200, Zürich Client private Architecture kämpfen für architektur ag, Zürich Construction engineers APT Ingenieure GmbH, Zürich Timber construction engineer Timbatec GmbH, Zürich Building services Naef Energietechnik, Zürich Timber construction Bächi Holzbau AG, Embrach Construction costs BKP CHF 1 833 000.– of which BKP 214 CHF 425 000.– Total property area SIA 416 1062 m2 Floor area SIA 416 789 m2 Energy reference area SIA 416/1 657 m2 Building volume SIA 416 2160 m3 Building envelope figure SIA 416/1 1.64 Cubic metre price SIA 416 (BKP2) CHF 849.– Redevelopment and addition of floor 2009, year of construction 1954

Embodied energy is measured according to kWp. Electrical auxiliary energy for space heating and hot water; for heat pumps it is already included. 42  The requirement for circulation in the energy network is estimated here. 43  Where the electricity requirement of the ventilation is stated in a Minergie certificate, these figures can be used in the first phase. 44  The electricity requirement of the air box system is estimated here; it is somewhat better than a fully developed ventilation system with heat recovery, as specified in the booklet SIA 2040 ‹SIA path to energy efficiency›, with a pre-project standard value of 6 MJ/m2. 45  For photovoltaics, the expected annual yield is used. But only if a building is also directly supplied and this renewable electricity is not resold, for example, through a cost-covering feed-in tariff (KEV). Otherwise it would be counted twice, because another household could buy this electricity. Periods during the day when excess solar electricity is fed into the network, or when electricity is obtained in return, are regarded as a zero sum game. 46  Visitors’ parking spaces do not need to be included in the calculation. 40  41 


67

Figure 53: The system boundary is the entire building.

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.2.2 Overall assessment according to SIA booklet 2040 ‹SIA path to energy efficiency› Calculation of non-renewable primary energy and greenhouse gas emissions of the multi-family building on the ‹Segantinistrasse›

Construction Building under ground Exterior walls Windows, balconies Ceilings, interior walls Roof Interior completion Building services Own production

Non-renewable

Greenhouse

primary energy

gas emissions

[MJ/m2]

[kg/m2]

0 8 2 22 1 13 9

0.0 0.4 0.2 1.6 0.1 0.7 0.6

26

1.7

3 17 100 60

0.2 1.0 6.4 5.0

15 10 0 2 12 12

40 26 0 5 32 32

0.6 0.4 0.0 0.1 0.5 0.5

25

66

1.0

–71

–186 10 250

–2.9 0.1 5.0

108 130

5.5 5.5

218 440

12.0 16.5

No intervention 267 m2 newly insulated, carrier panel for plaster, plastered 138 m2 new timber elements, timber cladding 191 m2 triple glazing wood and metal windows, 54 m2 balconies 28 m2 new concrete ceiling 69 m2 new roof superstructure, 132 m2 new roof 160 m2 flooring with underfloor, 225 m2 insulation on unheated areas Ground-source heat pump, distribution not new, plumbing, ventilation 12 m2 solar collectors Photovoltaic 15 kWp installed output 40

Total construction Reference value for construction εSPF Operation Thermal heat Hot water Ventilation 41 Lüftung 43 Lighting Operating facilities

Final energy [MJ/m2]

Qh = 59 MJ/m2, heat pump Qw = 50 MJ/m2, ⅓ heat pump, ⅔ solar collectors Central ventilation plant 42 Central ventilation plant 44 Standard value for pre-project according to SIA 2040, new lighting Standard value for pre-project according to SIA 2040, renewed 115 m2 photovoltaic installation on the roof 45

Own production Total operation Reference value for operation

3.9 2.0

Correction

Mobility 19 Estate type Building location Availability of season ticket Private car availability Parking spaces per household 46 Distance to shops in km Total Mobility Reference value for mobility Overall assessment Project value Target value for residential / conversion

factor

City core Well connected, public transport quality class B Swiss average

1.0 4.0 0.25

Swiss average 2 parking spaces for 6 households

0.65 0.3

Coop /  Migros, Meierhofplatz

0.75


68  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

The area of operation is crucial for the building’s excellent performance regarding target values. The extremely well insulated building envelope has reduced the previous heating demand by more than a factor of 5. The remaining heat demand is consistently met by renewable energies, which are harnessed locally on the property itself. The sunny location on the Hönggerberg is ideal for the use of solar energy. The fact that this energy type is used in this project for the production of electricity and heat shows the will to cover the building’s energy needs with as little reliance as possible on external sources. In the area of construction, the reference values for non-renewable primary energy are exceeded by more than 60 %, those for greenhouse gas emissions by around 20 %. The intervention in the existing building structure is mainly limited to the new cladding of the building envelope and the partial renovation of the building services. The high project values in the construction area are therefore surprising, at first glance. But considering that the new storey is a completely new construction, it is understandable that the project values are higher than the reference figures for conversions, and this fact can be significantly qualified: 20 % of the energy reference area of the building is accounted for by the new part. If the reference values for new construction and conversion from the SIA booklet 2040 ‹SIA path to energy efficiency› are weighted accordingly, we obtain values in the approximate area of those achieved at the ‹Segantinistrasse›. In the area of mobility, the good quality of the site is reflected in the project figures: the reference values are met. The low number of parking spaces – two parking spaces for six apartments (visitor parking spaces not included) makes a decisive contribution to this good result. The CCEM Retrofit Redevelopment method developed theoretically by Empa, FHNW and HSLU was applied here for the second time. 48 A new, more efficient construction process was tested, using prefabricated façade elements with integrated windows and ventilation ducts. The method is designed to shorten the construction time through standardisation and prefabrication and enables redevelopment to take place without the residents needing to leave the building. Despite a less than optimally structured building process, the potential of the method was demonstrated in this project.

8.2.3 Excursus: redevelopment as opposed to new construction The small multi-family house on the ‹Segantinistrasse› meets the target values easily. Especially with its greenhouse gas emissions, the building is at around 23 % below the target value. This observation can be generalized to some extent: redevelopments and alterations have an advantage from a total energy perspective. Building alterations, viewed from the perspective of the SIA booklet 2040 ‹SIA path to energy efficiency›, benefit from a considerably smaller use of embodied energy and lower emissions in the construction phase. A large part of the resource-intensive primary structure is already in place and no longer burdens the balance sheet. This is especially true for work under ground, which is not only cost- but also energyintensive. In addition – if the conversion can be done with reasonable intervention – a large part of the primary structure (ceiling, load-bearing interior and exterior walls, supporting columns) remains untouched. The two categories ‹building under ground› and ‹primary structure› make up around 35 % of embodied energy and 40 % of greenhouse gas emissions during construction, depending on the size of the building. For example, if during interior work (interior ceiling and wall coverings, floor structures including underlay) only half of the areas are renewed, a small apartment building – the building on ‹Segantinistrasse› is a typical example – can correspondingly halve the values a new building would produce. This applies even if the entire building envelope is newly insulated and clad, the windows are replaced and all the building services renewed. CCEM-Retrofit Advanced Energy Efficient Renovation of Buildings: http://www.fhnw.ch/habg/ivgi/forschung/ccem-retrofit

48 


69

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Figure 54: Calculation of embodied energy and greenhouse gas emissions of a small multi-family house in hybrid construction with 1000 m2 floor area (4 floors including basement, hybrid construction, 35 % window area), calculated with Grisli 

Comparison of the ecological impact of new construction and conversion New construction Conversion G’house gas emissions Embodied energy Embodied energy [MJ/m2] [kg/m2] [MJ/m2] Building under ground 13 1.3 Primary structure 24 2.4 Exterior walls / roof 17 1.0 Windows, balconies 18 1.2 Interior completion 20 2.1 Building services 21 1.3 Total 113 9.3

Figure 55: Embodied energy of a small multi-family house (1000 m2 floor area, hybrid construction). The grey-shaded sector does not normally apply for a conversion. In comparison to new construction (100 %), a comprehensive conversion only requires 60 % of the embodied energy.

Comparison of embodied energy for conversion / new construction Conversion / refurbishment

0 0 17 18 10 21 66

12 % 20 %

19 %

16 %

9%

15 %

  Building under ground   Primary structure   Int. completion ½

Figure 56: Greenhouse gas emissions of a small multi-family house (1000 m2 floor area, hybrid construction). The grey-shaded sector does not normally apply for a conversion. In comparison to new construction (100 %), a comprehensive conversion generates only 50 % of the greenhouse gas emissions in the construction phase.

G’house gas emissions [kg/m2]

9%

  Int. completion ½  Extension of exterior wall and ceiling

 Windows   Building services

Comparison of greenhouse gas emissions for conversion / new construction Conversion / refurbishment

14 %

14 %

13 %

11 %

26 % 11 %

  Building under ground   Primary structure   Int. completion ½

11 %

  Int. completion ½  Extension of exterior wall and ceiling

 Windows   Building services

0 0 1.0 1.2 1.1 1.3 4.6


70  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Various basic conditions were crucial for the decision ‹Conversion instead of a replacement new building› at the ‹Segantinistrasse›: The renovated building is the same size as the maximum allowed for a replacement building. As a new building would not have produced additional usage capacity, the most important reason for demolishing the existing building was eliminated. No underground work was necessary at the ‹Segantinistrasse›.  The existing building was in good condition and static reinforcement was not required, despite the additional floor. The heating demand was dramatically reduced by simple measures within the building envelope. In the case of a new building considerably more parking places would have had to be created at the ‹Segantinistrasse›. Since the parcel is not large, they would probably have been located underground, which would have been a burden on the new building not only from an energy, but also from a financial point of view.

Figure 57: The renovated multi-family house on the ‹Segantinistrasse› in Zurich with the addition of a floor in timber element construction. Photo: kämpfen für architektur ag

The decision ‹conversion or demolition / new construction› is not always easy. From an energy perspective a few general mnemonics can be given:  Redevelopment and conversion are worthwhile when a new building would not produce a significant enlargement of the building volume and useful area, when the existing building fabric allows for redevelopment without interference in the primary structure,  when the heating demand can be reduced with measures in the building envelope, and when the living conditions can be adapted to today’s quality requirements. All this applies to the multi-family house in the ‹Segantinistrasse›. As there are many buildings like this one in Switzerland, as mentioned above, a transfer of the knowledge gained and of the redevelopment measures selected is both possible and desirable.


71

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.3 Hughaus – a clever energy concept Example of the office / new construction building category Figure 58: The ‹Hughaus› with entrance area and main building in hybrid construction with prefabricated façade elements in timber construction and rearventilated cladding. Photo: Renggli AG, Sursee

Urban development / neighbourhood Hug AG has been producing bakery goods for over 130 years. The growing space requirements for jobs in the administration and for promotional purposes at the factory site are being met by a new building. The new office building is in close proximity to the production area, but is still in a near-natural environment: the area covers more than 10 000 m2 and comprises low-nutrient grassland and flowering meadows, interspersed with ponds. The austere, rectangular building stands out as a solitary building on the site, emphasising its special function. Project The building is large, with a length of 45 m and a width of 23.5 m. Thanks to a skylight in the roof above the stairwell of the building, the centre also receives sufficient daylight despite this remarkable building depth. The two floors of the office building can be seen from the entrance side. The ground floor is mainly reserved for contact with the public: this is where the company receives guests in the visitors’ centre and the ‹Chnusperladen›. An open staircase leads up to the office floor. 80 work places can be accommodated in the building. Thanks to the open and flexible office land-

scape, the rooms seem generous despite the relatively high density of work places. The basement, partially set into the ground, is mainly reserved for services, above all store rooms. The building has a classic hybrid design, mixing supporting columns, walls and ceilings of concrete and a nonbearing, prefabricated timber element construction on the façades. It was clear to the client at the outset that timber and local companies should be used for the construction process. Optimal management of resources is anchored as a principle in the corporate mission statement. Consequently, at least one Minergie standard was required for the building envelope, and as far as possible local energy sources were preferred. An exceptional energy concept was therefore implemented for this building. The office building uses the waste heat from the ovens and refrigerators in the nearby factory building (local heating network).


72  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.3.1 Construction, operation and mobility Construction The new office building is a simple cube and achieves a favourable compactness of 1.14 (total building envelope above and below ground divided by floor area). The large spans lead to a mixed design: the basement, storey ceilings, columns, stairs and wet areas are concreted. In contrast, the non-bearing walls are executed in timber frame construction. Swiss pine was chosen for the unpretentious façade cladding. In the basement, an outer concrete shell is used for the transition into the ground.

Figure 59: Cross-section through the façade

Inside the building there is a clear separation of systems: the piping is exposed, and there is little use of suspended ceilings. The horizontal pipes of the ventilation system thus remain accessible at all times for adjustments or cleaning.

Roof extension from the outside: Extensive green roof 80 mm Drainage fleece Roof sheeting Insulation 220 mm Flexible sheeting for waterproofing Reinforced concrete ceiling 360 mm Battens 30 mm / sound dampening insulation Acoustic board 25 mm

Ceiling: Covering 10 mm Anhydrite screed 70 mm Dividing layer Footfall sound insulation 20 mm Insulation 40 mm Reinforced concrete ceiling 360 mm Battens 30 mm / sound dampening insulation Acoustic board 25 mm

Exterior wall: Plasterboard 12.5 mm Vapour control layer OSB 15 mm Stud 220 mm / insulation OSB 15 mm Battens 50 mm Wooden façade 22 mm


73

Operation Through a mineral wool insulation of 220 mm on the façades the building achieves U-values of 0.19 W/m2K. In the year of construction, 2006, the heating demand of 138 MJ/m2 (standard air exchange) or 106 MJ/m2 (with actual air exchange) met the Minergie standard for the building envelope. The energy concept is based on locally available energy sources. 80 % of the heating demand is covered by the waste heat from the chillers of the nearby ‹tartelette› production facility. 20 % of the required heat production at peak times is provided by an existing oil heating system, however. The continued operation of this existing, unamortised investment may well make

Figure 60: Interior view of ‹Hughaus›. Photo Renggli AG, Sursee

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

sense for a limited period of time. The hot water, which is only available from a few taps in the building, is locally heated with electric boilers. The indoor cooling is achieved by ground water through the floor heating system and by a few additional cooling elements on the ceilings (‹silent cooling›).


74  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Mobility The office building is located on the premises of the bakery products manufacturer in Malters, about 300 m from the railway station. Nevertheless, a large proportion of the employees use their own car to come to work. On the site itself bikes are available, and these are in frequent use during the day. Malters is only moderately served by public transport (public transport-grade C). No special measures are being taken to support energy-efficient mobility behaviour. According to SIA 380/1 ‹Thermal energy in buildings›, a room height correction was included for excessively high rooms until 2007: rooms with a floor height > 3 m were allowed an addition to the energy reference area. In 2009 this room height correction was abolished.

49 

Figure 61: Location of the ‹Hughaus› in Malters. Public transport quality class C according to http://map.are.admin.ch

Footnotes for Figure 62, page 75.

Location Neumühlestrasse 4, Malters Client Hug AG Architecture Renggli AG, Sursee Construction engineer Berchtold + Eicher, Zug Timber construction engineer Makiol + Wiederkehr, Beinwil am See Building services Gloor + Sehringer GmbH, Reinach AG Timber construction Renggli AG, Sursee Construction costs BKP 1–9 CHF 6.5 million of which BKP 214 CHF 0.58 million Total property area SIA 416 ca. 4000 m2 Floor area SIA 416 3180 m2 Energy reference area SIA 416/1 2166 m2 (or 2809 m2 with height correction) 49 Building volume SIA 416 12 688 m3 Building envelope Figure SIA 416/1 1.45 (or 1.12 with height correction) 49 Compactness (entire building envelope in proportion to floor area) 1.14 Cubic metre price SIA 416 (BKP2) CHF 512.– Construction period March – December 2006

Electrical auxiliary energy for space heating and hot water; for heat pumps it is already included. Where the electricity requirement of the ventilation is stated in a Minergie certificate, these figures can be used in the first phase. Visitors’ parking spaces do not need to be included in the calculation.

41  43  46 


75

Figure 62: The system boundary is the entire building.

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.3.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› Calculation of primary non-renewable energy and greenhouse gas emissions of the Hug AG office building

Construction Building under ground Exterior walls Windows, balconies Ceilings, interior walls

1060 m2 floor slab, 320 m2 concrete wall against ground 720 m2 timber frame construction, timber boarding 150 m2 concrete base, interior thermal insulation 290 m2 triple glazing wood-metal windows, 48 m2 roof windows 2120 m2 concrete ceilings 58 concrete columns, 630 m2 concrete walls 1010 m2 concrete, flat roof construction 1600 m2 floor covering with underfloor, 680 m2 plasterwork Local heating network, electrical, plumbing, ventilation

Roof Interior completion Building services Total for construction Reference value for construction

Non-renewable

Greenhouse

primary energy

gas emissions

[MJ/m2]

[kg/m2]

13 4 1 10 18 3 20 16 25 110 130

1.2 0.4 0.2 0.7 1.7 0.3 1.5 1.2 1.6 8.6 10.0

εSPF [–] 1.0 0.9

Final energy

0 22

0 27

0.0 1.8

0.85

6 2

16 5

0.2 0.1

14

38

0.6

27

71

1.1

28

74

1.2

232 300

5.0 4.0

Total for mobility Reference value for mobility

246 230

12.8 11.5

Overall assessment Project value Target value for office /new construction

588 660

26.4 25.5

Operation Thermal heat

Hot water Auxiliary energy 41 Ventilation 43 Lighting Operating equipment

Qh = 106 MJ/m , of which 80 % is local heating and 20 % peak shaving with heating oil Qw = 5 MJ/m2, decentralised electric Standard value for pre-project according to SIA 2040 According to Minergie certificate (EBF adjusted) According to Minergie certificate (EBF adjusted) Standard value for pre-project according to SIA 2040 2

[MJ/m2]

Total for operation Reference value for operation Mobility

Correction factor

Building zone Building location

Small local working area Moderately connected, public transport quality class C Season ticket availability Swiss average Availability of bicycle Available parking Availability of parking 55 parking spaces for 80 employees spaces 46 Company car Electric car

0.4 0.0 0.22 1.0 0.69 5 % of journeys


76  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

The building, constructed in 2006, has been optimised for efficient operation. Optimisation with respect to energy consumption for construction or mobility was not yet an issue in the process. Nevertheless, the building reaches the target value for embodied energy without difficulty. The target for greenhouse gas emissions, on the other hand, is not met: the project value is around 3 % above the target value. Although most of the heating demand can be met with waste heat from the factory’s own production, the results in the field of operation are rather disappointing. Closer examination shows that in particular the peak

Figure 63: Presentation of various project values for the overall assessment, based on three different variants for peak shaving (replacement of the oil heating system). In addition, a variant is included with own electricity production and heating unchanged. The system boundary is formed in each case by the entire building.

shaving of 20 % of the heat demand by the existing oil heating system is a sensitive CO2 driver. If this oil heating, which was still in existence at the time of the new building project, could be replaced in future and peak shaving met by renewable energy sources, the target for greenhouse gas emissions could be met, as shown in figure 63.

Project values of non-renewable primary energy and greenhouse gas emissions for the ‹Hughaus› from the overall assessment

Variant: project value with peak shaving by woodchips Variant: project value with peak shaving by pellets Variant: project value with peak shaving by a heat pump for ground water Variant: project value with own production of electricity: 200 m2 photovoltaic module Target value for office / new construction

This situation is specifically foreseen in the SIA booklet 2040 ‹SIA path to energy efficiency›: buildings qualify as SIA energy efficient when they are designed to achieve both target values through measures in the field of building services. Nevertheless, the route for a building from SIA energy efficiency-capable to energy efficiency-compliant needs to be mapped out. The figures for the variants in figure 63 show that if peak shaving is provided by woodchips, pellets or a heat pump, the goal can be reached. Alternatively, the large roof area of the building could be fitted with photovoltaic modules: some 200 m2 of photovoltaic panels with a capacity of about 20 kWp would be sufficient to lower the project value to the required level. Conscious use of resources is part of the company’s mission statement, as already mentioned. Local building materials were accordingly preferred: Hug decided on timber element construction for the external walls and cladding in wood. This and the fact that a simple, functional building form was chosen are reflected in the excellent values for the construction of the ‹Hughaus›. The actual value for greenhouse gas emissions in construction is around 13 % below the reference value. The particular emphasis on the exciting energy concept in publications on this building obscures the fact that its simplicity and economical use of materials are probably its greatest contribution to energy efficiency. Two small measures help to attain a more conscious use of mobility despite the unfavourable initial situation: there are bicycles available on the premises that

Non-renewable

Greenhouse

primary energy

gas emissions

[MJ/m2]

[kg/m2]

562 566 573 492 660

24.6 24.8 24.7 25.3 25.5

are enthusiastically used for the journey to lunch. For years, the company has also owned a small electric car. Despite these measures, the values in the area of mobility are clearly missed. However, the deficiency in mobility is compensated by the outstanding results in construction. In the area of operation, an effort in the area of building services seems an obvious measure to take: better peak shaving by the local heating system does not seem possible at present because the heat is dependent on the production programme and the production times. When no production takes place at the turn of the year and there is no waste heat, the offices are completely dependent on the oil heating system. Probably the peaks could be shaved without too much effort and without using fossil fuels – wood or pellets would be an obvious choice of alternative energy sources – or by the installation of photovoltaic panels on the roof. The Hug building is therefore ‹SIA energy efficiency-capable›.


77

8.3.3 Excursus: energy sources The influence of energy sources on the result in the area of operation is considerable, often greater than that of a low heating demand due to a better insulated building envelope (see Section 4.3.3). The following

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

summary illustrates this, based on the example of peak shaving of the heating demand of 20 MJ/m2 in the ‹Hughaus›.

Figure 64: Calculation of the non-renewable primary energy and greenhouse gas emissions of various energy sources. Performance ratio, primary energy factors and greenhouse gas emission coefficients are shown according to the booklet SIA 2040 ‹SIA path to energy efficiency›.

Resource expenditure for peak shaving of room heat using the ‹Hughaus› as an example

Figure 65: Non-renewable primary energy in MJ/m2 for peak shaving of 20 MJ/m2 shown for different energy sources

Non-renewable primary energy: comparison of different energy sources

Non-renewable

Greenhouse gas

primary energy

emissions

[MJ/m2]

[kg/m2]

27 8 5.6 13 1.6

1.8 1.0 0.3 0.2 0.08

With heating oil (perf. ratio η 0.9) With biogas in earth gas quality (perf. ratio η 0.9) With pellets (perf. ratio η 0.75) With ground water heat pump (COP ε 4.1) With woodchips (perf. ratio η 0.75)

25 20 15 10 5 0 Heating oil

Figure 66: Greenhouse gas emissions in kg/m2 for peak shaving of 20 MJ/m2 shown for different energy sources

Biogas

Pellets

Heat pump Ground water

Woodchips

Heat pump Ground water

Woodchips

Comparison of greenhouse gas emissions of different energy sources 1.60 1.20 0.80 0.40 0.00 Heating oil

Biogas

Pellets


78  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

There are considerable differences between the energy sources that could be used to meet the same heating demand. With non-renewable primary energy, the difference between oil heating and woodchip heating is a factor of 17, for greenhouse gas emissions the factor is 23. The figures for the heat pump, powered by the Swiss electricity mix, are particularly striking: electricity, in particular nuclear power, needs a great deal of energy for its generation, but emits relatively few greenhouse gases. The great importance of the choice of energy source and at the same time the significantly shorter lifetime of the building services compared to the building envelope can justify a staggered investment in the building envelope and building services for the purpose of compliance with the SIA efficiency path. Especially if an existing and still possibly not amortised heating system can be used, or if the financial situation requires it, then improvement of the building services can justifiably be postponed. The condition, though, is that retrofitting or modification of the building services will be part of the planning process for new

Figure 67: Interior view of ‹Hughaus›. Photo Renggli AG, Sursee

construction or conversion at a later date, so that the required measures can be easily implemented and will not fail due to inappropriate building design. A clear system separation between primary, secondary and tertiary structures, as was implemented in the ‹Hughaus›, should therefore always be sought. The fact that further operation of the oil heating system is possible in the ‹Hughaus›, but that the high greenhouse gas emissions of this system could be compensated by electricity production on the large roof area, is an example of the flexibility which is characteristic of SIA efficiency path thinking.


79

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.4 Eichmatt school – one big building instead of two small ones Example of the school / new construction building category Figure 68: The ‹Eichmatt› school building with its façade of prefabricated, non-load-bearing and highly insulated timber elements, with larch cladding on both sides. Photo: Hannes Henz

Urban development / neighbourhood The two communities of Cham and Hünenberg held a project competition in two stages with the requirement that the Minergie-P standard should be adhered to and the embodied energy optimised (SNARC 50). Already in the project competition, the approach of Bünzli  & Courvoisier clearly showed itself to be the most efficient. In the competition, but also in the project planning process, calculations of the embodied energy were carried out for important milestones and corresponding optimisation was achieved. The early orientation of the project planning to an energy-efficient approach facilitated the architecturally demanding implementation of the project. The measure with the greatest influence on sustainability had already been taken by the two communities of Cham and Hünenberg before the competition: the cooperation between the two communities led to the decision of residents to build a large school instead of two smaller ones on land jointly acquired. As regards urban development, the new school building is orientated towards the new Eichmattstrasse. Its distinctive, elongated volume gives the location and the building an identity which is appropriate for its public use. The new building uses the site skilfully, in that only two of its floors are seen from the west, where the playground and sports area are located, while three floors are visible from the public meeting zone in the east.

Project The new building is marked by the contrast between its outward appearance of compact volume and its division into various zones of use, determined by the multifaceted space allocation plan. Spacious entrance halls connect the entrances and provide access to the space units. Three small atria, open to the sky, serve as orientation points, provide extensive vistas and allow adequate daylight into the interior rooms, despite the considerable depth of the building. The approximately 110 m long and approximately 25 m wide building includes a lower and two upper floors. A special construction method was used: the walls and ceilings are in solid construction. The load transfer of the ceilings at the walls takes place through laminated wood and not concrete columns. This is a new design and shows an innovative use of timber in hybrid construction. The façade consists of precast, non-bearing and highly insulated timber elements with larch boarding on both sides. A ground-source heat pump in conjunction with floor heating provide the heating and cooling. All units are of the highest efficiency rating. The photovoltaic panels on the roof provide electricity to the grid; they are not allocated to the building. The building achieves a high Minergie P standard and has been awarded the ‹Gutes Innenraumklima› label (good indoor climate label). SIA documentation D0200 ‹SNARC – Systematik zur Beurteilung der Nachhaltigkeit von Architekturprojekten für den Bereich Umwelt›; 2004. http:// www.eco-bau.ch (System for assessing the environmental sustainability of architectural projects)

50 


80  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.4.1 Construction, operation and mobility Construction The compact, elongated building has a consistent rhythmic structure throughout. The arrangement of the windows overrides the rhythm of the supporting structure, so that the load-bearing supports are sometimes behind

windows, and sometimes embedded in the non-structural timber elements. The double gymnasium is spanned by glulam beams over the entire depth of the building.

Figure 69: The load transfer of the ceiling at the façade takes place through laminated timber columns. Photo: Hannes Henz

Figure 70: Cross-section through the façade

Ceiling: Anhydrite screed 60 mm Footfall sound insulation 20 mm Reinforced concrete 280 mm Perforated plaster panel, suspended 140 mm

Exterior wall: Boarding in oiled larch 20 mm Battens 41 mm Vapour barrier Three-layer panel 19 mm Cross bars 120 mm / insulation Cross bars 260 mm / insulation Cross bars 120 mm / insulation Wind proofing membrane Battens 30 mm Boarding in larch 20 mm

0 0.1

0.5

1m


81

Operation The heating demand of the new school building is extraordinarily low, at 39 MJ/m2. This is achieved by a thick insulation system on the façades (340 to 500 mm, U-values from 0.1 to 0.07 W/m2K) and on the roof. Due to this, the building also achieves the

high Minergie-P standard. The building is heated and cooled by a ground-source heat pump in conjunction with floor heating. A ventilation system with heat recovery ensures sufficient air exchange and minimal heat losses.

Energy flow diagram for the ‹Eichmatt› school building

Heat pump COP ε: 4.5 Electricity 37 000 kWh

165 000kWh

Room heating / ventilation 119 000 kWh

School Gym Flat caretaker

Geothermal probe ‹Cooling› 113 000 kWh

Hot water 46 000 kWh

Geothermal probe ‹Heating› 128 000 kWh

Figure 71: An electrically operated heat pump converts geothermal energy into usable heat for heating and domestic hot water. In summer, excess heat is returned to the ground. Source: Meierhans + Partner AG

Climate-friendly and energy-efficient construction with wood – Basic information and implementation


82  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Mobility The school’s location on the border between the two communities is developing, but is currently still a fringe area. It achieves the C grade for public transport. Mobility is less important for schools than for other building categories: students do not usually

Figure 72: Location of the school on land belonging to the communities of Cham and Hünenberg. Public transport quality class C according to http://map.are.admin.ch

Footnotes for Figure 73, page 83.

have motorised transport and come to school on foot or by bicycle. Teachers and parents who bring their children to school by car are responsible for most of the energy consumption for mobility where school buildings are concerned.

Location Chamerstrasse 11, Hünenberg Client Einwohnergemeinde Cham und Einwohnergemeinde Hünenberg Architecture Bünzli & Courvoisier, Zürich Construction management b + p baurealisation ag, Zürich Construction engineer Aerni + Aerni, Zürich Timber construction engineer Makiol + Wiederkehr, Beinwil am See Building services Meierhans + Partner AG, Schwerzenbach Timber construction ARGE Xaver Keiser Zimmerei, Zug, und Burkart AG Trilegno, Auw Construction costs BKP 1–9 CHF 29.2 million of which BKP 214 CHF 1.65 million Total property area SIA 416 19 079 m2 Floor area SIA 416 8580 m2 Energy reference area SIA 416/1 8119 m2 (or 11 000 m2 with height correction) 49 Building volume SIA 416 38 160 m3 Building envelope Figure SIA 416/1 1.10 (or 0.81 with height correction) 49 Compactness (entire building envelope in proportion to floor area) 1.15 Cubic metre price SIA 416 (BKP2) CHF 639.– Construction period February – October 2009

Where the electricity requirement of the ventilation is stated in a Minergie certificate, these figures can be used in the first phase. Visitors’ parking spaces do not need to be included in the calculation.

43  46 


83

Figure 73: The system boundary is the entire building.

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

8.4.2 Overall assessment according to booklet SIA 2040 ‹SIA path to energy efficiency› Calculation of primary non-renewable energy and greenhouse gas emissions of the ‹Eichmatt› school building

Construction Building under ground Exterior walls Windows, balconies Ceilings, interior walls

3640 m2 insulated floor slab, 757 m2 insulated concrete walls, 103 m2 roof under ground 2190 m2 timber element construction, timber boarding 1440 m2 triple glazing wood and metal windows 4740 m2 concrete ceilings 6920 m2 interior concrete walls 3280 m2 concrete, flat roof construction 7180 m2 floor covering with underfloor; parts without underfloor Ground-source heat pump, electrical, plumbing, ventilation

Roof Interior completion Building services Total for construction Ref. value for construction

εSPF Operation Thermal heat Qh = 39 MJ/m2, heat pump Hot water Qw = 14 MJ/m2, heat pump Ventilation 43 According to Minergie-P certificate Lighting According to Minergie-P certificate Operating equipment Compilation of actual equipment Total for operation Ref. value for construction Mobility

Non-renewable

Greenhouse

primary energy

gas emissions

[MJ/m2]

[kg/m2]

15

1.2

4 11 6 13 18 12 24 103 110

0.2 0.7 0.7 1.0 1.5 0.7 1.4 7.4 9.0

24 18 42 94 15 193 180

0.4 0.3 0.6 1.9 0.2 3.0 2.5

54 60

2.9 3.0

350 350

13.3 14.5

Final energy [MJ/m2]

4.3 2.0

9 7 16 36 6

Correction factor

Construction zone Building location

Not only a working area Moderately connected, public transport quality class C Season ticket availability Swiss average Bicycle parking availability Available Availability of parking 46

Ca. 1 parking space for 2 employees

Total for mobility Ref. value for mobility Overall assessment Project value Target for office / new const.

0,0 0,0 0.22 1.0 0.69


84  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

The school achieves the target values. It shows exceptionally good results in the area of construction, especially for greenhouse gas emissions. This is explained by the large, compact volume and the hybrid construction method selected. Compared to the other categories of buildings, the spaces in school buildings are often excessively high, and thus generate a small energy reference area in relation to their volume. Although the larger surface areas do involve higher energy expenditure in the construction phase, this is offset in typical school buildings by their typical largescale structure. In the area of operation the reference value is not achieved, despite the very high standard of the building envelope: the power consumption for ventilation, lighting, etc. remains high – as is typical for a school building. The photovoltaic system installed on the roof does not feed its yield into the school building and is therefore not counted. 20 Nevertheless, this electricityproducing facility does benefit both of the surrounding communities and could theoretically cover a large portion of the electricity needs of the school building. For mobility, the figures are below the reference values. This is not unusual for school buildings, as they are usually in the vicinity of residential areas and being important public buildings are often well connected to the public transport system. Moreover, mobility is generally less important for schools, because the energy demand for mobility for the overall surface area is distributed among relatively few teachers.

Figure 74: Calculation of the embodied energy and greenhouse gas emissions of different façade claddings. The claddings are each mounted with the rear ventilation level directly on the insulated timber element (without exterior insulating layer). As the weight of the cladding becomes greater, the amount of material needed for the substructures also increases. Manufacture including disposal, not amortised. Calculated with Grisli

3.4.3 Excursus: façades In almost all the projects presented here, wood was chosen not only for the supporting structure, but also for the outer cladding. External timber cladding for weather protection shows the best results in both green energy and greenhouse gas emissions compared with various other claddings. There are also many arguments for using wood as a substructure. A comparison of various claddings, based on the square metre of façade area, shows a wide range of resource intensity. The amortisation time for the various rearventilated façade claddings is always set at 40 years, according to the SIA booklet 2032 ‹Embodied energy of buildings› – in contrast to non-rear-ventilated systems, which are given an amortisation time of 30 years. Of course these are simplifications: wooden shuttering, especially if it is painted or stained, needs more maintenance work, if it is really to attain 40 years’ service, than claddings with higher weather resistance such as fibre cement sheeting, fibreglass reinforced concrete panels or metal façades.

Embodied energy and greenhouse gas emissions of six different façade claddings

Timber boarding on timber substructure Fibre cement, small format, on timber substructure Carrier panel for plaster, plastered, on timber substructure Glass-fibre-reinforced concrete panels on metal substructure Titanium zinc sheeting on timber boarding, timber substructure Aluminium composite metal façade on special light metal substructure

Cladding Substructure Total Cladding Substructure Total Cladding Substructure Total Cladding Substructure Total Cladding Substructure Total Cladding Substructure Total

Embodied energy [MJ/m2] 41 60 101 85 60 145 185 60 245 255 120 375 417 60 477 660 255 915

Greenhouse gas emissions [kg/m2] 3.4 3.3 6.7 8.5 4.6 13.1 8.9 4.6 13.5 15.2 8.6 23.8 25.3 4.6 29.9 43.5 19.2 62.7


85

Figure 75: Embodied energy (non-renewable primary energy) in MJ/m2 for different claddings including substructure, calculated with Grisli

Comparison of embodied energy of façade claddings 900 800 700 600 500 400 300 200 100 0 Wood boarding Fibre cement Coreboard, slates plastered  Substructure

Figure 76: Greenhouse gas emissions in kg/m2 for different claddings including substructure, calculated with Grisli

Glass-fibrereinforced concrete panels

Titanium zinc sheeting on timber

Aluminimum composite panels

Glass-fibrereinforced concrete panels

Titanium zinc sheeting on timber

Aluminimum composite panels

 Cladding

Comparison of greenhouse gas emissions of façade claddings 60 50 40 30 20 10 0 Wood boarding Fibre cement Coreboard, slates plastered  Substructure

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

 Cladding

The differences in values for façade cladding, related to the building component, may be as high as 5 to 10 % for construction, depending on the building size and the ratio of façade to windows. Taking the example of the ‹Eichmatt› school, the results in the construction

phase would be about 5 % worse for embodied energy and greenhouse gas emissions if aluminium composite panels were used instead of larch boarding for the façade cladding.


86  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

9

Implementation of energy generation and smart building services

9.1

Primary energy demand and greenhouse gas emissions

Resource-saving and environmentally friendly buildings are not only the result of energy-optimised building standards, but frequently also of active energy generation on site. The ‹Grünmatt› estate (see Section 8.1) and the administration building of the Hug Bakery (see Section 8.3) show how the requirements of 2000-watt properties can be fulfilled through an integrated approach. In the first case, the waste heat of nearby industrial and service companies is used, in the second the manufacturing facility provides sufficient energy for heating. But there are other suitable ways to provide heat locally apart from the waste heat potential which is often underused, namely solar energy, geothermal energy (ground-source heat pump) and renewable fuel wood. Half the heat that is produced domestically from renewable energy supplies comes from Switzerland’s native forests. In 2010, a total of 7 TWh of heat were produced. Compared to fossil fuels, or to the sun and ambient heat, wood used for heating involves an exceptionally low percentage of non-renewable primary energy, which makes it a suitable heat source for sustainable buildings. It is not only building materials that pollute the pool of finite resources: energy systems should also be evaluated in terms of primary energy demand and greenhouse gas emissions. Neutral or low-emission energy sources such as wind, solar and biomass themselves burden the environment, at the latest in the active production and conversion stages, through furnace systems, heat pumps or solar panels, and thus have an

Figure 77: Source: Primary energy factors of energy systems V2.2, ESU 2011

impact on the climate. According to the SIA booklet 2032 ‹Embodied energy of buildings›, energy systems must be assessed not only in terms of nonrenewable energy demand but also greenhouse gas emissions. For energy wood, this is achieved by calculating the cumulated energy demand for harvesting in the forest, transport and processing into a usable form. Primary energy factors set the energy content of fuel against the total energy required for the processing chain (see figure 77). Since the process for the production of wood pellets, for example, is more complex than that for chopped woodchips or wood, its primary energy factor is higher. Similarly, specific greenhouse gas emission coefficients specify the ratio between final energy consumed and greenhouse gases emitted during the production process, including combustion in the central heating plant. 51 The primary energy factors and the greenhouse gas emission coefficients of the energy systems are scientifically determined (‹Primary energy factors of energy systems, Version 2.2, April 2011›, ESU Services) and are part of the ‹LCA data in the construction sector›, which are continuously updated by the Coordination Conference of Federal Construction and Properties Services (KBOB) (cf. Section 3.4.1).

51 

Primary energy factors and greenhouse gas coefficients at the output of the energy converter Energy source Primary energy factor (non-renewable) [–] Heating oil (extra light) 1.23 Natural gas 1.11 Ground-source heat pump waste water (COP 3.4) 1.00 District heating (waste-to-energy plant) 0.05 District heating (wood) 0.10 Wood (firewood) 0.05 Wood (woodchips) 0.06 Wood (pellets) 0.21 Biogas 0.37 Solar collectors (room heating and warm water) * 0.24 Geothermal energy (COP 3.9) * 0.70 Ambient air (COP 2.8) * 0.95 * Energy measured at the output of the energy converter

Greenhouse gas emission coefficient [kg/MJ] 0.083 0.066 0.022 0.001 0.013 0.004 0.003 0.01 0.045 0.011 0.016 0.018


87

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

9.2 Wood heating: a broad range of applications The choice of fuel must be matched to operational requirements. Woodchips and wood pellets are suitable for automatic combustion plants with high power requirements (see figure 79). The latter are also a suitable variant for smaller apartment buildings. The use of firewood heating systems, however, remains limited to use in detached houses. These systems – from central heating systems to stoves – are fed by hand and filling the furnace once per day is sufficient. If they are also combined with an energy storage device, they provide a flexible complement to the primary heat source. Such a combined energy concept is used for the compact Nyffeler detached house in Hüttwilen, which was built by the Bauatelier Metzler to the passive house standard: the major portion of heat energy is supplied by a small heat pump with an output of only 500 W. In addition, there is a wood storage heater with an output of between 1 to 5 kW, which can be immediately

put into operation in transitional periods or as required (see figure 45). Theoretically the boiler or the water heating system could be supplied as well. To keep the building services simple in the Nyffeler home, this option is not being used. But in this two-storey residential house, the storage variant could in future be expanded without difficulty by means of a satellite. The loadbearing timber project implemented by the Bauatelier Metzler meets the highest energy efficiency standards. The heating demand of the Nyffeler home corresponds to a 2-litre house, calculated in fuel oil equivalents per square metre. This economical level is comparable to the ‹Eichmatt› school building (cf. Section 8.4).

Figure 78: Storage heating stove as a supplement for energy-efficient homes: interior view of the Nyffeler detached house Photo: Bauatelier Metzler

Figure 79: Selection of fuel types versus output requirement of the wood heating system

System variant Automatic boiler

Manually loaded boiler

Stove (storage heater)

Pellets Small and larger residential buildings (detached, multifamily); composite systems and district central heating plants Rare; small homes (detached houses)

Firewood Not available

Additional heating; small homes (detached houses) with good insulation

Most frequent use

Small homes (detached, multi-family)

Woodchips Large apartment buildings (multi-family houses); composite systems and district central heating plants Not available

Not available


88  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

9.3

Biomass: energy in the high temperature range

Wood heaters and combustion plants each offer efficient operation for various load requirements. Wood burners, which are suitable for the supply of low-energy homes and therefore have a low power rating (up to 10 kW), are certifiable as Minergie modules in their own right. An important reason to switch to wood heating is, however, heat supply in the high temperature range, and often heating replacement in existing buildings whose envelope may not be significantly changed for historic preservation or other architectural reasons. The Zurich Zurlinden building cooperative (BGZ), known hitherto as the pioneer of multi-story, 2000-watt-compatible housing developments using loadbearing timber, is proving in a current renovation project that the choice of the high-temperature variant ‹wood› can also be economically advantageous. The Sihlweid high-rise apartments, located in the Leimbach district in the south of Zurich, are being converted and refurbished. To enable the heating circuit and the radiators to be retained in the 170 apartments, the natural gas connection is being cut off and replaced by a new wood heating system. Combustion of pellets will continue to provide the necessary high flow temperatures for the heating of homes and hot water. The new pellet combustion system will supply not only the two high-rise buildings, but also the immediate neighbourhood, a shopping centre and an indoor pool. The renovation of the two 33-year-old high-rise buildings will last until 2013, after which the target values of the 2000-watt efficiency path (cf. Section 4) will be met. In addition to the replacement heating system,

9.4

the energy efficiency of the building envelope needs to be improved. The two towers will each receive a surrounding solar facade which will produce 48 000 kWh of electricity per building. This amount will cover about half of the total demand. The wood-burning district heating network in turn benefits from the fact that storage capacity is available and the original fuel oil tanks in the basement of the tall buildings can be converted. Wood-fired heating only comes into question for a redevelopment if there is sufficient space for the wood. Two years ago, the non-profit Winterthur housing cooperative (GWG) decided to replace its oil heating for environmental reasons. However, this could only be implemented because the tank room in the basement of the GWG estate, consisting of 24 homes, is large enough to store wood pellets and is also directly next to the old and new boiler room, which minimises the conveyor distance and thus the chance of disruption. The new wood heater has been operating faultlessly since its inception. To increase operational efficiency, it is combined with a solar thermal system, which provides hot water. The cooperative administration has, however, noted a slightly higher operating expenditure for heating with wood pellets than with oil. Very often such systems are therefore operated under contract by specialist companies or energy suppliers.

Wood-fired heating under contract

In the immediate vicinity of the Sihlweid high-rise buildings there is another large housing estate owned by the Zurlinden cooperative: six years ago, the ‹VistaVerde› estate, with 117 apartments, was constructed to the Minergie standard (see figure 80). The power supply comes from the locally available resources: the ‹duo› of sun and wood. The solar collector system on the 225 m2 of roof area produces 107 MWh of heat per year, representing about a quarter of the demand for hot water production. The estate is mainly heated by

a 350 kW woodchip system. There is an additional gas boiler to shave the peak loads and as a supplement in the summer. The heating system is operated on a heating contract: the timber construction company which supplies the fuel is responsible for running and maintaining the system. Incidentally, there is a requirement that the fuel must come from the neighbouring forest.


89

Figure 80: View of the ‹VistaVerde› estate, which has been heated with woodchips for six years. The hot water is generated by solar panels, and an additional gas boiler provides peak shaving. The heating system is operated on a contract basis. Photo: Holzenergie Schweiz. Figure 81: Feeding a silo with woodchips at the ‹VistaVerde› estate. Photo: Holzenergie Schweiz.

Regional electricity and natural gas utilities have begun to expand their activities to include the contracting of wood burning heating installations. For investors, this is often a welcome low-risk offer, because the contractor builds and funds such systems and in return is paid for heat generation and supply. New projects are being implemented in the Swiss Central Plateau: the Solothurn power company AEK is gradually developing a woodchip heating network in the existing ‹Leuenfeld› complex in Oensingen. About five million francs are

9.5

being invested to convert the energy supply for approximately 250 housing units from an oil-fired system to a woodchip plant. When the system is complete, the output of the AEK heating network will be approximately 2500 kW. The community of Oensingen is also involved in the extensive wood heating network – as a future timber supplier.

Renewable energy in networked systems

The city of Winterthur exemplifies the importance of securing the supply chain to operate a heating system. In the urban area there are half a dozen different large combustion plants with outputs between 69 kW and 900 kW; these supply a number of large residential and commercial buildings with heat for heating and hot water. The wood required comes only from the city’s own forests. The largest plant supplies three commercial buildings and approximately 700 homes in the Gern neighbourhood. The cooperative project, the ‹Wyden woodchip central heating plant with local heating network› is also structurally innovative. For the first time the operations centre, which went online in the autumn of 2011, has been sited underground, below a newly built school house. For efficiency reasons, it is a bivalent system: the connected public buildings and the adjacent residential district are supplied with thermal energy, of which 70 % is produced from wood and 30 % from natural gas. The latter provides peak shaving and covers reduced demand in summer. There is a clear trend towards better exploitation of locally available wood energy potential, mainly in large joint projects and networked

Figure 82: Source: Holzenergie Schweiz

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

Air quality requirements of wood heating systems Boiler variant Power range Carbon monoxide Firewood up to 300 kW 600 mg/m3 Chips up to 300 kW 300 mg/m3 Pellets up to 300 kW 250 mg/m3

supply systems: even today, the largest share of wood energy is burnt in automatic woodfired systems with an output of 50 kW. Large systems have recently seen an increase almost 30 %. New heating networks are in demand in both rural and urban residential areas. Ecologically and economically large systems make perfect sense: the dust collection technology of large furnaces is mature and has fewer specific particulate emissions than heating systems in individual buildings (see figure 82). The other advantage of a composite system is heat recovery, because the exhaust gases from damp fuel (water content greater than 45 %) can be used for condensation. Low return temperatures (below 50 °C) and a broad temperature spread allow the moist exhaust gases to be used for preheating the return flow. The use of exhaust emissions increases energy yield by 20 %, thus reducing fuel requirements and boiler output.

Hydrocarbons 20 mg/m3 15 mg/m3 10 mg/m3

Particulate matter Efficiency 50 mg/m3 83 % 60 mg/m3 85 % 40 mg/m3 85 %


90  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

9.6 Polyvalent supply concepts Networked supply systems often use several energy sources, because this can enhance the operating efficiency of the composite system. A typical example is the combination of wood-fired systems that provide the bulk of the energy required using fossil fuel boilers which shave peak loads during the heating season and secure low-load operation in the summer. The fact that the additional heating demand can be met with renewable energies is demonstrated by the Blaufuhren district heating network in the Emmentaler community of Sumiswald. The use of wood energy is supplemented by a solar energy system, which won the Solar Prize 2011, awarded by the Solar Agency Switzerland. The project is implemented on a self-help basis: 24 residential properties are now connected to the network, of which the householders have also become joint owners. The 200-kW wood burning system supplies the

base load demand in winter, for which purpose the central storage unit is stocked with a volume of 7000 litres. Outside the heating season the central heating plant operates for only two hours a day, however, so as not to compete with the additional solar thermal system. Not only is the 75 m2 roof area of the central heating plant covered with solar collectors, but also the other single-family homes connected to the network have decentralised plants to supply themselves with solar heat. The district heating solution is designed to provide private homeowners with an ecological substitute for their previous oil or electric heaters. The network was initiated two years ago, and the final stage is not yet in sight. Property owners who would like to be connected are required to install their own solar heating system (cf. figure 83 and figure 84).

Figure 83: Interior and exterior view of the central heating plant of the Blaufuhren wood district heating network with solar thermal installation Photos: Sommerheizungen

Figure 84: District heating network plan so far with individual connections in the residential quarter of Wasen BE. Source: Sommerheizungen

District heating network plan in the residential quarter of Wasen

  Already connected

  Connection by ca. 2014

  Connection by ca. 2018


91

A considerably more complex network of energy suppliers and consumers will in future be implemented in the Zurich Friesenberg district. Here too, the energy use of wood plays an important role: in a few years, energy with a high heat level will be generated from biomass and made available primarily to the extended Triemli city hospital, which is expected to fulfil the targets of the 2000-watt society. Because hospitals require a great deal of energy and also different heat levels – from hot water (160 °C) for hygienic requirements to low-temperature heat (38 °C) for heating patients’ rooms – a great deal of heating energy is produced on site by the hospital itself. As a first priority apart from the new woodchip plant, a geothermal probe will be needed, to be used with the help of heat pumps. Any

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

surplus will be consistently used as waste heat. But the city hospital is not only internally networked: the new energy centre with its woodchip plant will one day be connected to the waste heat network and a storage reservoir, from which the adjacent residential district around the newly reconstructed ‹Grünmatt› estate will be supplied (see Section 8.1.1, figure 42).

10 Energy figures as measures of energy reduction To reduce energy consumption after the energy crisis in the 1970s, an initial measure was the stipulation of maximum thermal transmittance values (U-values) for exterior building components in construction regulations. The

U-values were continually adjusted downwards over the years to reduce energy losses from buildings.

10.1 Transmission heat losses of buildings Another step was the calculation of the transmission heat loss of buildings. All energy losses from external components were added together, which enabled the entire building to be characterised for the first time. With the progressive improvement of the thermal standards of the building envelope it became evident that other factors are decisive for the total energy demand of a building, such as ventilation heat losses. In a well insulated house the losses that are caused by the change of air necessary for hygienic reasons are larger than the transmission heat losses through the building envelope. This development was taken into account with the establishment of low-and especially ‹nearly zero-energy buildings›, which are currently being constructed, for example, to the MuKEn or Minergie P standards. As a targeted improvement measure, low-energy buildings normally have a ventilation system with heat recovery, and in the case of nearly zero-energy buildings this is compulsory. Such a system reduces ventilation heat losses and provides additional user comfort through a guaranteed supply of fresh air. Airtight construction,

which is now taken for granted, resulted from these considerations; it not only reduces heating demand, but also lessens the chances of structural damage. Further information about this topic can be found in Section 4.1.2.


92  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

10.2  The energy performance certificate based on the SIA booklet 2031 ‹Energy certification for buildings› The energy indicators which are specified in the building energy certificate (GEA) are the specific heating demand or specific final energy demand, based on the energy reference area. The heating demand represents an energy balance sheet with gains and losses, as shown in figure 85. It allows comparison and calculation of transmission and ventilation heat losses and

Figure 85: The heating demand shows the difference between gains and losses. Source: HFA

energy gains through solar radiation or internal loads. The heating demand is the amount of energy needed to keep the building at the desired internal temperature in the heating season.

Energy balance with gains and losses Losses

Gains

Ventilation / Transmission Internal / Solar

Heating demand

– 60

– 50

– 40

– 30

– 20

– 10

As shown in the preceding chapters, the heating demand is a subset of operation, according to the SIA booklet 2040 ‹SIA path to energy efficiency›. Unlike this booklet, however, the building energy certificate in accordance with the SIA booklet 2031 ‹Energy certification for buildings› deals with total primary energy (renewable and non renewable). The two should not be confused, but the latter holistic perspective, as described in Section 4.3.4, means that e. g. biomass as a fuel shows different results, because the energy content of the energy source is included in the calculation. However, the building energy certificate (GEA) also emphasises the method by which the energy for the reported heating demand, as well as lighting and operating equipment, is produced. The energy demand of each of the energy sources is also converted into primary energy demand, which represents the amount of energy needed by upstream process chains outside the system boundary during the generation, conversion and distribution of the energy source. This is based on the final energy demand, which comprises the amount of energy that reaches the end consumer, and thus takes into account the efficiency of the building services system (net energy delivered). The final energy level is the figure used to characterise the energy quality of a building required by the directive 2002/91/eg. 52 By multiplying the final energy demand for each energy source by the corresponding primary energy factor, we

0

10

20

30

40

obtain the primary energy demand or the net primary energy supplied; this is not explicitly required by the above directive, but will certainly be approved. This annual primary energy consumption, together with CO2 emissions, represents the last and most significant level of key energy figures, due to the inclusion of primary energy sources such as wind, solar, gas, etc. and conversion losses. Based on the annual primary energy consumption, the share of renewable primary energy which is produced by wind, solar, biomass etc. will be shown separately as a percentage. For the ‹Segantinistrasse› property (see Section 8.2) the building energy certificate (GEA) of the Swiss Association for tested quality homes VGQ is shown as an example. The VGQ-GEA is based on the SIA information sheet for 2031 ‹Energy certificate for buildings› (2009 edition). Directive 2002 ⁄ 91⁄eg of the European Parliament and the Council of 16 December 2002 on the overall energy efficiency of buildings

52  


93

Calculated energy certificate

VGQ-GEA 12000

1954

Energy renovation in year: 2009

Address:

Segantinistrasse 200, CH-Zürich

Energy reference area AE in m2:

If applicable per zone in m2:

657

Calculated energy demand

-

The annual energy demand was calculated using the standard values. Climate station: Zurich

Very energy-efficient Sehr energieeffizient

A

B

C

Primary energy PrimärenergieKennwert specific value

Heizwärmebedarf Heating demand

A

A

abbr. Production system

0% 100 %

D

E

F

300 %

G

21 050

MJ

12 167 13 718

13 718

H+WW

MJ

eE,V

MJ

15

Annual energy consumption as primary energy in GJ: 2

Annual energy consumption per AE in MJ/m :

98

17

% of SV1

Heating energy demand QH in MJ/m2:

59

37

% of LV2

Annual greenhouse gas emissions in tons:

0.93 5

% of SV1

2

Annual greenhouse gas emissions per AE in kg/m :

1.42

2

Heat in MJ/m :

2

33

Electricity in MJ/m :

71

Weber Energie und Bauphysik, Bern

Bern, 2012-19-03

16 425

Photovoltaic system

E4

MJ

-46 358

Wind generator

E5

MJ

0

Net energy supplied

EP

MJ

21 707

Primary energy factor

fp,j

-

Net primary energy supplied

Ep

MJ

AE

2

m

ep

MJ/m2

2.97 64 471 64 471 657

%

Greenhouse gas emission coefficient

kCO2

kg/MJ

Net greenhouse gas emissions

MCO2

t

mCO2

17 0.043 0.93

0.93 1.42

%

14.9

15

GJ

9.6

9.6

RCO2,09

%

Renewable primary energy share

fren EP,ren

Renewable primary energy

570

1.42

kg/m

Greenhouse gas emission specific value

Signature

98

2 eP,std,2009 MJ/m

RP,2009

Greenhouse gas emission figure

The correctness of this information is confirmed by: Heinz Weber Name of the company:

7 884

MJ

Primary energy specific value

Annual own energy production from renewable sources:

0 8 988

MJ

Limit value 1

0

eE,L

Energy index

64

0

eAp,std

Energy reference area

A

Greenhouse gas emission class:

2

9 939 21 050

WW

Production system

Lighting

Renewable primary energy in %:

Place, date:

MJ

Production system

Operating equipment

Less Wenigenergy-efficient energieeffizient

1

H

Ventilation

200 %

unit

Electricity CH-Mix

multi-family house

Year of construction:

Weighted total demand

Building / Building part / Utilisation unit:

Total auxiliary energy

This energy certificate was created in accordance with the booklet SIA 2031:2009

Energy demand

Figure 86: The VGQ’s building energy certificate. The clear layout and easily understandable calculations quickly show the energy efficiency of a building, which also allows a later success check in the operation phase. The energy index is the demand for heating or the final energy demand. Source: VGQ

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

2

5

Standard value Limit value according to SIA 380/1

VGQ-GEA-12000

page 1 of 2

VGQ-GEA-12000

page 2 of 2

In figure 87 the characteristic values are summarised for the four properties from Section 3, in accordance with the VGQ’s building energy certificate. Figure 87: Values per square metre of energy reference area and year. Calculated according to the data sheet SIA 2031, 2009 edition ‹Energy certificate for buildings›. To facilitate comparison with values based on the data sheet SIA 2040 ‹SIA path to energy efficiency›, the demand for lighting and operating equipment has been calculated in accordance with the assumptions in Section 8, and for electricity according to the Swiss consumer mix. For the mixed-use property ‹Hughaus› the default values were determined proportionally to the surface areas.

Characteristic values and classification of the four buildings from Section 3 ‹Grünmatt› estate ‹Segantinistrasse› ‹Hughaus› office apartment building building 98 251 Primary energy consumption [MJ/m2] 143 Proportion of renewable primary energy Standard value according to SIA 2031 Primary energy characteristic value

[%]

Heating demand QH

15

‹Eichmatt› school 212

15

12

15

[MJ/m2] 570

570

464

340

[%]

17 (A)

54 (B)

62 (B)

[MJ/m2] 101

59

106

39

Standard value according to SIA 2031 Heating demand characteristic value

[MJ/m2] 116

160

128

124

[%]

37 (A)

83 (B)

31 (A)

Greenhouse gas emissions

[kg/m2] 2.07

1.42

5.01

3.08

Greenhouse gas emission characteristic value

[%]

5 (A)

22 (A)

18 (A)

25 (A)

87 (B)

7 (A)


94  Climate-friendly and energy-efficient construction with wood – Basic information and implementation

The primary energy characteristics of the four buildings are, considering the total primary energy (renewable and non renewable), in classes A and B. To make the data better comparable with the overall assessment according to SIA data sheet 2040 ‹SIA path to energy efficiency›, the same figures as in Section 3 were applied to the ‹Grünmatt› estate regarding the energy requirement for circulation in the environmental energy network and waste heat utilisation. For the ‹Hughaus› the use of district heating is therefore disregarded. Due to the very low energy requirements for heating and the use of solar energy the ‹Segantinistrasse› building achieves the best value. The heating demand characteristic value for the ‹Segantinistrasse› and ‹Eichmatt› properties is in the A class. Both properties reach the Minergie-P standard, which is also reflected in the building energy performance certificate. The ‹Grünmatt› and ‹Hughaus› properties have a heating demand of 80 to 90 % of the default (limit value according to the SIA standard 380/1 ‹Thermal energy in building construction›) and are thus in the B class. The four properties also achieve very good results for greenhouse gas emission characteristic values. They are all in the A class. The ‹Grünmatt›, ‹Segantinistra-

Figure 88: CO2 reduction effects due to timber growth, calculated on the basis of the CO2-Bank Switzerland, and, as complementary information, the absolute greenhouse gas emissions generated by the construction and operation of the reference properties covered in this issue.

sse› and ‹Eichmatt› properties all have heat pumps and solar systems. The ‹Hughaus› building uses the waste heat from the refrigeration of the tartlet production to cover heating demand, which is not recognized in the calculations, as in Section 8. Excursus CO2-reduction: Simple approach for a clear picture Based on the amount of wood used for construction, the CO2 reduction during the growth phase of timber can be calculated as explained in Chapter 1.2. In figure 55 this effect is estimated for the properties described in Section 3. For size comparison, these values are set against the absolute greenhouse gas emissions caused by construction and the annual greenhouse gas emissions during operation. It should be noted that, following leaflet SIA 2032 ‹Embodied energy of buildings›, the cumulated quantity of greenhouse gases (CO2, methane, nitrous oxide and other gases affecting the climate) are expressed as CO2 equivalent emission amounts (see section 7.2).

CO2 reduction effects and absolute greenhouse gas emissions CO2 reduction due to timber Greenhouse gas emisisions caused by construction growth [t CO2] ‹Grünmatt› estate 184 554 ‹Segantinistrasse› apartment 39 122 building ‹Hughaus› office building 78 724 ‹Eichmatt› school building 378 2230

For the ‹Grünmatt› estate, the greenhouse gas emissions caused by construction were reduced by around 33 %, due to forest growth corresponding to the timber used in construction. This reduced amount corresponds to the greenhouse gas emissions over an operating period of 92 years. In the ‹Hughaus› and ‹Eichmatt› properties, the supporting structure is largely made of concrete. This means that CO2 reduction due to the use of wood is lower. Nevertheless, the CO2 reduction due to the timber external walls and façades is still equivalent to 10 – 17 % of the absolute greenhouse gas emissions generated by the construction

Greenhouse gas emissions in operation [t CO2 per year] 2.00 0.07 10.8 24.4

process. The ‹Segantinistrasse› apartment building in Zurich is a fifties building in solid construction. The facade elements for the rehabilitation of the building envelope and the new attic storey in timber construction are responsible for a CO2 reduction of 39 tons. This represents approximately one third of the greenhouse gas emissions caused by the construction.


95

Climate-friendly and energy-efficient construction with wood – Basic information and implementation

11 Outlook

The vision shared by politics, voters 53 and scientists is a way into the future which stabilises our climate emissions at a climate-compatible level. According to the Energy Science Centre (ESC) at the ETH Zurich, this means that towards the end of the 21 Century the primary energy demand should be between 4 and 6 kW per person. The exact value depends, among other things, on developments in energy efficiency as well as on the proportion of electricity produced from CO2free primary energy (renewable primary energy). 54 The use of Swiss wood already makes a significant contribution to reaching this goal. This is because, apart from the advantages mentioned in this publication, Swiss timber also brings the added benefit of very short transport routes. With its innovative strength, the Swiss timber industry is well on the way to establishing itself as an important branch of a regional and global ‹ecoeconomy›. This new global field of economic activity and work offers a large ‹bouquet› of possibilities and is supported by intensive research and development. Environment This publication shows that one of the questions that need to be asked first and foremost in the context of sustainable construction regards expected changes in the environment. System boundaries must be open and (later) networking and adaptation must be possible, particularly because the answer to the question of how the environment will change is often unclear. Building with wood offers a high degree of flexibility. For example, large spans (and correspondingly flexible spaces) can be implemented and the conversion of wooden structures is also simple. In the context of the conversion of existing buildings, the low weight of the building material makes adding floors in wood possible, and it is self-explanatory that renovating the energy systems of old building envelopes with prefabricated wall elements is a rapidly growing application of timber construction, 55 which is remarkably efficient in this sphere. It is well known that material efficiency can be improved either by using less raw material for the final product, or by reducing the amount of material used in the production process. Both of these criteria are fulfilled by wood: it is a lightweight material that leads to streamlined and efficient structures, and its ease of processing minimises the use of resources in production. In addition, waste material from the manufacturing process can be immediately used for heating.

the roadmap for global climate policy that the Climate Conference in Durban produced in December 2011. This is not an argument for a lack of ambition in climate policy, though – because delaying measures to curb the greenhouse effect will exacerbate rather than ease it. In Switzerland, according to the revised federal law on the reduction of CO2 emissions, which passed the final votes in the councils in the winter session of 2011, greenhouse gas emissions should be reduced overall by 20 percent of 1990 levels by 2020. 56 The revised CO2 Act provides that the reduction should take place domestically, and should include the environmental performance of wood used in construction. Article 14 explicitly states: ‹The performance of the sinks of timber used in construction is allowable.› As is shown in the present publication, there are instruments containing target or limit values for reaching the specified climate policy goals within Switzerland’s building stock, or for achieving even higher goals. For example, the SIA prescribes maximum values for embodied energy and greenhouse gas emissions in its booklet SIA 2040 ‹SIA path to energy efficiency›. Such target values are basically still voluntary, and the next few years will show how successful the implementation of the various non-binding guidelines has been. However, as explicitly mentioned in federal law, voluntary measures should also contribute to reductions. Even if the currently available tools and calculation aids may yield impractical results under certain conditions and in some situations, this does not diminish the value of the approach. The tools and instruments will be refined and improved with experience. During the application of measures and the implementation of climate-friendly and energy efficient buildings, the holistic approach underlying the search for solutions will necessarily dictate the following guiding principle: the details of every solution have an effect on the whole and must be carefully considered and intelligently applied. As shown in this publication, the façade system selected for a school building, for example, can save about 120 tonnes of CO2-eqiv. Over 40 years if wood is used instead of aluminium. This difference is approximately equivalent to the CO2 emissions of an individual over 20 years. At least in the regions of Switzerland where there have already been votes on this subject, as in the city of Zurich. There the majority of voters at the end of 2008 were in favour of adopting the vision of the 2000-watt society in the municipal code.

53  

Unlike the 2000-watt society, the ESC does not suggest an upper limit for primary energy, but for CO2 emissions. This CO2 target, which according to the ESC should not be exceeded by individuals, is one ton of CO2, which in the long term will only be achievable through extensive use of solar energy.

54  

Statutory and voluntary guidelines Greenhouse gas emissions, particularly CO2 emissions, which are due to the use of fossil fuels should be reduced internationally in order to help limit the global temperature increase to less than two degrees Celsius. This goal is scarcely achievable according to

An example is the current research project TES-EnergyFaçade of the Technical University of Munich.

55  

Federal law on the reduction of CO2 emissions of 23 December 2011

56  


Imprint Lignatec Technical information on wood from Lignum Publisher Lignum, Swiss Timber Industry, Zurich Christoph Starck, managing director Coordination Olin Bartlomé, dipl. Holzing. FH, Lignum, Zurich Figure credits Figure 15: Hannes Henz, Zurich / Lignum; figure 16: EM2N Architekten, Zurich / Lignum; All other figures without indication of source within the publication originate from the authors and Lignum. Pre-press BN Graphics, Zurich Administration / distribution Andreas Hartmann, Lignum, Zurich Print Kalt-Zehnder-Druck AG, Zug Translation Nick Bell, Hirzel

The Lignatec series provides information on technical issues regarding the use of wood as a construction and raw material. Lignatec is intended for planners, engineers, architects and manufacturers and processors of wood. Lignatec is increasingly being used at all levels of education and training. A loose-leaf binder can be obtained from Lignum. Members of Lignum will receive a copy of each Lignatec publication free of charge. Further copies for members CHF 15.– Single copies for non-members CHF 35.– Loose-leaf binder (empty) CHF 10.– These prices are subject to change. The copyright of this publication is owned by Lignum, Swiss Timber Industry, Zurich. Reproduction is permitted only with the express written permission of the publisher. Disclaimer This publication was produced with the utmost care and to the best of the publisher’s and authors’ knowledge and judgement. They are not liable for any damage or loss which may occur through its use or application. LIGNUM Holzwirtschaft Schweiz Mühlebachstrasse 8, 8008 Zurich Tel. 044 267 47 77 Fax 044 267 47 87 info@lignum.ch www.lignum.ch Lignatec 25 and 26/2012 Climate-friendly and energy-efficient construction with wood – Basic information and implementation First published June 2012 English edition: 2000 copies ISSN 1421-0320


Climate-friendly and energy-efficient construction with wood – Basic information and implementation