massive wood + urban infill + energy efficiency

AA E+E Environment and Energy Studies Programme Architectural Association School of Architecture Graduate School March Sustainable Environmental Design Dissertation Project 2009-11

Massive timber construction: An energy efficient urban infill in London

Fanor Serrano February 2011

Abstract The study explores the use of massive timber prefabrication in urban applications specifically small gaps referred as urban infill.

The project explores the specific characteristics of the prefabricated massive timber construction such as airtightness and thermal mass that can be incorporated in the environmental strategy for the energy efficiency of buildings in urban context.

The project also plots a framework in order to incorporate and extend the environmental good characteristics of the massive wood into a low impact way of producing buildings through extension of the building’s life span, low impact production processes and energy efficient operation.

2|P a g e

Acknowledgments I would like to express my gratitude to the tutors of the SED program; I would also like to acknowledge David Grindley architects and Antony Mc Guinness for helping me with information and access to their houses.

Finally special thanks to Colfuturo for the financial support.

3|P a g e

1 Contents Abstract ........................................................................................................................................................... 2 Acknowledgments ........................................................................................................................................... 3 2

Introduction ............................................................................................................................................. 6

3

Theoretical background ........................................................................................................................... 7 3.1

Urban infill and massive wood construction ......................................................................................... 7

3.2

Embodied energy and waste ................................................................................................................. 8

3.2.1

The construction industry environmental impact ............................................................................ 8

3.2.2

Massive wood construction and reduction of construction impact ............................................... 11

3.3

4

5

3.3.1

The use of energy in the UK the residential data ........................................................................... 20

3.3.2

Massive wood construction and the provision of thermal comfort ............................................... 21

Context and precedents ......................................................................................................................... 25 4.1

Context and climate ............................................................................................................................ 25

4.2

Precedents and fieldwork ................................................................................................................... 27

4.2.1

Calewen .......................................................................................................................................... 28

4.2.2

The office ........................................................................................................................................ 34

4.2.3

Stadthaus ........................................................................................................................................ 37

4.2.4

Acharacle primary school- Argyll, Scotland .................................................................................... 41

Analytic work ......................................................................................................................................... 44 5.1

Benchmark: ......................................................................................................................................... 44

5.2

Comfort ............................................................................................................................................... 44

5.3

Environmental strategies .................................................................................................................... 46

5.3.1

Winter: ............................................................................................................................................ 46

5.3.2

Summer: ......................................................................................................................................... 46

5.4

6

7

Use of energy ...................................................................................................................................... 20

Thermal analysis.................................................................................................................................. 46

5.4.1

Material characteristics .................................................................................................................. 46

5.4.2

Winter performance ....................................................................................................................... 51

5.4.3

Summer........................................................................................................................................... 59

Research outcomes and applicability ..................................................................................................... 63 6.1

Production and construction............................................................................................................... 63

6.2

Energy use ........................................................................................................................................... 66

6.3

Extended use of the building .............................................................................................................. 68

6.4

Demolition and material recycling ...................................................................................................... 69

Design application. ................................................................................................................................. 70

4|P a g e

7.1

Design Framework / brief ................................................................................................................... 70

7.1

Site ...................................................................................................................................................... 71

7.2

Building ............................................................................................................................................... 75

7.3

Parts .................................................................................................................................................... 78

7.3.1

Basic construction order ................................................................................................................. 78

7.3.2

Element sizing (fabrication – and offsite): ...................................................................................... 79

7.3.3

Module design and occupant use: .................................................................................................. 80

8

Conclusions ............................................................................................................................................ 98

9

References ............................................................................................................................................. 99

10 Appendix .............................................................................................................................................. 102

5|P a g e

2 Introduction This dissertation project started as a research on the possibilities and applications of massive wood construction under an environmental point of view. It was extended to its application in an urban context by the use of small sites or gaps of the city referred here as ‘urban infill’.

As possibilities to use neglected sites, urban infill projects are proposed also as an opportunity to densify the urban fabric without additional investment on infrastructure. Considering these conditions, massive wood technology can be considered adequate for different reasons. Some of them being: Less disruption to adjacent buildings because of the short time spent on site as well as together with its advantages in relation with off-site production. This can also be considered to be an important economical factor.

Less foundation required than other type of constructions due to its lightness; which also minimizes the disruption of adjacent buildings.

Simplicity of detailing, and possibility of being prefabricated and case- specifically produced.

Characteristics affecting the thermal performance of building like Air tightness and thermal storage capacity.

Under this premises, this report aims to concentrate on the environmental impact of wooden buildings in urban infill applications in relation with its main aspects: the construction environmental impact (waste and embodied energy) and the operational energy.

1. EMBODIED ENERGY AND WASTE: The construction industry is responsible for an enormous negative environmental impact represented by pollution waste and energy consumption, directly related to the materials commonly used. In this sense, the extended use of wood in construction has the potential to diminish such impact.

Even though, despite its inherent good environmental qualities, it’s potential in the reduction of the construction environmental impact can be diminished or improved depending on design factors.

In this sense, the first objective of this dissertation is to generate a framework for design within where this potential can be augmented, framework that would be tested in the design application component of this dissertation 2. OPERATIONAL ENERGY CONSUMPTION: In urban sites important factors of the passive solar design are affected because of its inherent restrictions: in urban conditions direct solar radiation is often obstructed in winter and unobstructed in summer.

Due to its prefabricated nature, the massive wood construction can provide airtight structures less dependent on solar gains in winter. As well, the thermal mass of the wood can make possible ventilation strategies for peak hot days in summer like the use of night ventilation.

Having this in consideration, the second objective of the study is to incorporate and test these characteristics (airtightness and thermal mass)of the massive wood technology through analytical tools as well as to propose an environmental strategy adequate for the material and for the urban application.

6|P a g e

3 Theoretical background 3.1 Urban infill and massive wood construction

Figure 3-1 Covent Garden urban gaps, London- Aerial view-image: Bing maps

The urban infill projects offers the possibility of a more dense and compact urban fabric using the existing voids in the city and therefore the creation of additional habitat; This Without the need of the investment in infrastructure network (ways, transport, sewage, etc) The use of sites closer or even part of the central areas of the city promotes living ways with less dependence of transportation due to the proximity to services.

But despite these advantages, the urban infill also faces some challenges: The available sites for urban infill have been usually neglected due to its difficult onsite logistics. The construction process itself represents a disruption of the life of the neighbours and the construction process, especially in the foundation stage, can affect adjacent structures.

For these reasons prefabrication in massive wood is an adequate technology to use in urban gaps because the material is lighter and requires fewer foundations and the time spent in the construction site, as well as the machinery needed is reduced by prefabricated construction.

7|P a g e

3.2 Embodied energy and waste 3.2.1 The construction industry environmental impact Studies on mass the balance of the materials used by the construction industry in the United Kingdom that measure waste, pollution and energy consumption of the construction industry (Griffiths, Kersey, & Smith, 2002) provide an insight on the weighting of different aspects of the construction and final disposal of buildings in the environmental impact of construction.

When waste is analysed, 38.9% is coming from quarry waste, 1.3% from material and product manufacture and the 59.8% from construction and demolition waste.

Even though this percentage is related to the high proportion of the use of quarry materials in relation with others, it also implies that the move towards materials like wood could have a positive impact because of its more efficient use of waste in production and higher recycling value.

The figures (See Figure 3-2) for energy consumption show that the energy used in the production of materials and products is the higher percentage: 50%. This followed by the energy used in transport of such materials: 21%. When, to this percentage is added the transport of waste from demolition and site activities, the total transport percentage represents 40% of the energy used.

From the pollution and emissions of greenhouse gasses (measured as CO2 equivalents), the higher percentage is, by far, related to mineral extraction product and material manufacture (71.2%), followed by construction and on site activity (14.5%). This leads again to a high potential of the wood construction in relation to the reduction of emissions in the productions stage.

The efficiency of the construction and material production processes is an additional problem. The data for the year 1998 shows that the addition of mass to the built environment in the UK can be estimated on 275 Mt; for this mass of buildings was required an input of 420Mt of material resources which means that in the process nearly a 35% of the resources were transformed in waste at some point. This waste implies additional energy input in its final transport and disposal among other environmental consequences.

The most important factors in reducing the waste from buildings are (in order of magnitude): the waste generated on site from demolition and construction processes, followed by the waste generated from production.

From the perspective of energy used, the reduction of energy consumption in the production stage possesses the larger potential; the production stage as well has the bigger potential for the reduction of the pollution.

8|P a g e

Transpor relating to construction site activity 828 11%

Transport of wastes from product and material manufacture 13 0%

Construction site activity 872 11% Transport of secondary and recycled materials 433 5%

Transport products and materials 1630 21%

Transport of construction and demolitioin waste 140 1.8%

Mineral extraction, product and material manufacture 3927 50%

Figure 3-2 Summary of energy consumption by the construction industry in kilo tonnes of oil equivalent (Ktoe) and percentage of total- After: (Griffiths, Kersey, & Smith, 2002)

9|P a g e

Figure 3-3 UK Mass balance – The grey areas represent mass (Mt), the yellow ones represent energy (Mtoe).After (Griffiths, Kersey, & Smith, 2002)

10 | P a g e

3.2.2 Massive wood construction and reduction of construction impact 3. 2 .2 . 1 M as s iv e w o od c on s t ru ct io n The massive wood construction is a construction technique based on the use of wood panels usually made of small planks of wood that are tied together either mechanically or glued.

The panel’s size is usually restricted by transportation or plant space limits.

One characteristic of this kind of panels is that the wood used in its production is of a lower structural grade than the one used in other wood construction applications and as the planks are tied together shorter elements can be used allowing the use of pieces of wood with knots usually unfeasible for structural applications.

An additional advantage of the massive wood construction and is its potential for 1 the use of local species, as TRADA affirms, The processing of the panels is done via computer numerical machines (CNC) and operations as routings and perforations are then possible (KLH UK) Once in the construction site, the panels arrives pre-cut and with openings and the prefabrication of big elements such as walls including insulation, waterproof layers and windows is also possible, (see Figure 3-6) When the panels are made by planks glued together the recycling value of the wood as bio-mass can be diminished as some adhesives require special furnaces to be burned, due to the toxic gasses product of the combustion process.

A technique of mechanically fixed planks without the use of nails or glue called Brettstapel, mentioned above by TRADA, has been used recently in Scotland (see case studies: Acharacle primary school) When using the Brettstapel technique, the planks made of softwood usually spruce are tied together by the use of hardwood dowels usually made of beech when the elements reach moisture equilibrium the dowels expand mechanically fixing the planks together (Bridgestock, Foster, & Henderson, 2010)(See Figure 3-5).

Variations of this principle use dowels not perpendicular but diagonal to the plans (See Figure 3-4), in order to avoid displacement of the planks cause by temperature variations (Bridgestock, Foster, & Henderson, 2010)

1

“Because of our relatively mild and wet climate, much home grown timber is too fast growing so inadequate for structural grades. (…) the Brettstapel method has raised heads here, is a possible future solution for using more locally sourced timber in structural applications” (TRADA, 2010)

11 | P a g e

Figure 3-4 Brettstapel panel - diagonal dowels (Sohm)

12 | P a g e

Figure 3-5 Brettstapel principle

Figure 3-6 Massive wood – Glued Cross laminated panels in factory (Thompson, 2009)

13 | P a g e

3. 2 .2 . 2 Be ne fi t s o f th e w o od c on s t ru c ti o n Timber construction has the potential of reducing the construction environmental impact. This by extending the efficiency on the reuse of waste, little embodied energy and cleaner processes in a field actually dominated by concrete and steel construction.

Because of its vegetal nature, wood stores solar energy and close to 50% of the wood’s mass is carbon absorbed by the plant in form of carbon dioxide trough photosynthesis. As CO2 stored by trees would only be released when the material is burned or decayed, the use of timber in building construction implies that the sequestered carbon will be out of the atmosphere as long as the building exists.

(Berge, 2009).

It is also important to mention that no fuel energy is needed and no pollution is released during the raw material production and the material itself and its waste are an energy source: the combustion value of wood exceeds the energy required to process the material (Berge, 2009) and the waste can be re-used as fuel in the production chain or recycled for another wood based materials like chip boards or fibber boards (Wegener & Zimmer, 2004). Additionally, the end of the life of the building the wood elements could be re-used or burned as source of energy.

In relation to the reuse of waste, some examples of manufactures in the production chain includes its use as bio-mass for the production of the energy used in the transformation of the wood into building elements (KLH UK) , also sold as raw material for boarding or bio mass pellets; others the use of wood shavings as insulation material (Baufritz UK ltd).

This could lead to a production chains with no external energy input (KLH UK) 3. 2 .2 . 3 Pr ef a b ri c at i o n Prefabrication has been characteristic of wood construction due to the material flexibility and when referring to prefabrication in wood, it does not mean standardized or mass produced identical elements (Davies, 2005).

Also, and opposing what is usually assumed, the efficiency of its production does not affect its possible high level of customization.

When talking about UK’s development in relation with prefabrication, the level of industrialization of Timber construction is high .The construction plans are processed in factory and adapted to fabrication that is usually CAD/CAM controlled whit a high level of accuracy.

Another important characteristic is that prefabrication can improve the quality of construction representing improvements in the thermal performance of buildings.

In relation to this, the good quality of joints between elements is a condition needed to minimize the air infiltration and thus the heat losses associated, which is a requirement fulfilled when using this type of elements.

3. 2 .2 . 4 Du r ab il it y and se cu r i ty A premature decay or demolition of a building implies the erection of a new one, and, evidently, a waste of resources (energy, materials, money, etc). Additionally, in the case of the wood, carbon stored is released as CO2 when the wood decays or is burned, condition that as analysed before would act against the benefits of the wood construction.

The CO2 sequestration values are calculated based in certain duration or building life span of 50 to 100 years (Berge, 2009), short life-spans mean lower rates of Carbon storage and also a risk of over exploitation of the resource as it has no time to re-grow. In this sense is important explore the aspects related to the durability of wood buildings.

14 | P a g e

Natural durability: As a natural material, the wood will decay. Its main risks are fungi and insects attacks. (Dinwoodie, 2000) The fungus attack occurs when the humidity content of the wood is above 20%.

The wood can be protected when designing the project in order to keep it protected: parts of the building must not remain wet and should be allowed to dry.

In massive systems the thick wood layer acts as regulator of the internal humidity as in its bigger volume can store it; this also gives to the massive buildings the 2 characteristic of regulate the internal humidity of the spaces .

In order to prevent the attack from insects, impregnation of the timber with pesticides is usually employed, but as this is not commendable from an environmental point of view. Alternatives as heat treatment (kiln dry) or impregnation with harmless chemicals as natural alcohols or oils are an option.

The principle is to create a layer of wood without nutrients appealing to the insects.

Fire security: In the UK as well as in other countries, doubts about the security of wood construction are related to fires in the past, which as consequence lead to ban multi-storey construction in wood in until recent times.

In the UK experimental research has been done through a laboratory-building called TIMBER FRAME 2000 (See Figure 3-7,Figure 3-8). The building was exposed to fire in different situations to assess the performance of the building and its elements (for instance all wood stairs). The data obtained proved that timber frame buildings can meet requirements of building regulations in the UK in terms of limiting the internal spread of fire and the structural integrity (TRADA in association with UK timber frame association, 2007) (Grantham & Enjily, 2003) which are the main criteria to assess the fire performance of a building’s safety to fire.

The structural integrity of the building during a completely developed fire (being important how much time can the building resist without collapsing), is a condition in which wooden structures performs very well. This due to the fact that the charred layer acts as an insulator and can delay the rise of temperature in the interior of the structural elements. In this sense, a common practice to achieve good structural resistance of elements under fire conditions is to increase it section.

The charring rate of the spruce is 0.76 mm/min (KLH UK) which means that 23mm of additional thickness in the exposed face of the elements can provide a resistance of 30 min under a developed fire. (TRADA in association with UK timber frame association, 2007) The surface spread of flame, or in other words how the fire is spread by the surfaces of the building is and aspect in which the wood performs badly because it’s flammable nature.

This condition is usually solved with the use of layers of plasterboard or the use of additives that can bring exposed elements of timber to levels that accomplish the existing building regulations. Additional studies and experimental work (Grantham & Enjily, 2003) affirm that resistance to fire accomplished by individual elements can be safely achieved on buildings.

Another solution to the surface spread problem is the use of water sprinklers that could bring additional protection, taking into account that in a room exists always the possibility of additional flammable elements (books, furniture, etc)

2

In layered construction systems as timber frame, special care is needed to prevent the vapour penetrating the walls from the inside towards the exterior causing interstitial condensation in the cold layers of the walls. This is called interstitial condensation and is a usually problem solved by the use of vapour barriers (Edwards, 2005).

15 | P a g e

Figure 3-7 Timber Frame 2000 Testing building.

Figure 3-8 Timber frame 2000 Testing building – controlled fire (Grantham & Enjily, 2003)

16 | P a g e

3. 2 .2 . 5 Ad ap t ab il i t y The life span of a building depends not only of the durability of its materials but also of the adaptability of the structure to changing requirements.

When referring to flexible housing author defines flexible in the following way: â€œâ€Śis housing that can adjust to changing needs and patterns, both social and technological. These changing needs may be personal (say an expanding family), practical (i.e. the onset of old age) or technological (i.e. the updating of old services).

The changing patterns might be demographic (say the rise of the single person household), economic (i.e. the rise of the rental market) or environmental (i.e. the need to update housing to respond to climate change). This definition is deliberately broad...� (Till & Schneider, Flexible Housing, 2007)

Figure 3-9 Adelaide Road- London GLC architects Nabeel Hamdi and Nick Wilkinson- (Till, Wigglesworth, & Schenider, Flexible housing)

The given opportunities for the building to change are thus expressed by the indeterminacy of the building at different scales: either the possibility to subdivide or expand the flats, or the possibility of use spaces for different uses to the provision of excess or un-built space (Till & Schneider, Flexible Housing, 2007) , but also considering questioning the sizing of spaces by deterministic assumptions on the function they are going to serve.

17 | P a g e

Another author (Berge, 2009) takes a similar approach and classifies the opportunities of the building to change in three main categories: Generality: or the possibility of the spaces to be used to different purposes. This means certain level of indetermination in the characteristics of the spaces.

Flexibility: or the possibility to change the internal layout along time.

Elasticity: or the possibility to grow or expand in an easy way.

The subject of flexibility has been explored by many architects, an example of this is the Adelaide road project in London, designed to allow different internal configurations, as the load bearing walls are provided with non structural soft zones allowing coupling and decoupling of spaces vertically and horizontally (see Figure 3-9).

The nature of changes within a building has been described as they occur at different frequencies for its different elements or layers. Certain parts of a building are meant to last more than others. (James & Brand, 1997) In this category, provision for the change in the layers that are mean to change at higher speeds should not affect or been affected by long lasting layers (see Figure 3-10).

A common situation in relation to layering and that brings into account prefabrication, is the constructive logic of the prefabricated elements. This is the case for example of prefabricated service pods that compromise the structure when put together on site leaving little possibilities of change without compromising the structure (Till & Schneider, Flexible Housing, 2007) this approach makes the internal layout inflexible and thus the building vulnerable to fast obsolescence.

Figure 3-10: The main layers of a building

source: (Berge, 2009) after (brand, 1994)

Recycling value: One of the most noticeable advantages of the wood against other forms of construction is the large range of possibilities of the material of being recycled. It can be done in different ways: the structural elements can be reused, considered as valuable recycled material, or in other cases, wood can also be reused as material for boards like chip board or as a source of energy (Wegener & Zimmer, 2004) (Berge, 2009).

18 | P a g e

The recycle value of elements in a building is strongly related to the purity of materials. In practice the separation of glued layers of different materials for recycling is not practical and usually more expensive that the recycled material. In this sense, raw materials fixed with mechanical connections are preferable; boards and elements composed in a high percentage of glue are contaminant waste (contrary to the raw wood) and require special furnaces for burning.

Allowing the reuse of elements is preferable because is the one that involves less additional processes and will imply bonding of the CO2 for larger periods. In this sense materials should be fixed together in a way that can be removed easily.

Obviously, pure raw pure wood has the best options for being re-used or recycled.

And special care is required in the provision of connections between elements that allows dismantling the elements according to the duration rates.

Adaptability of the comfort strategy: Additional to the above categories, is important to mention that the adaptation of buildings can also be promoted from a comfort / energy consumption point of view.

Buildings designed for specific use should allow changes in its environmental strategy if required; avoiding obsolescence if the change occurs. Changes in use often imply changes in the density of people in the spaces, different schedules, smaller or bigger dwellings etc.

This analysis is going to be addressed ahead (chapter 5.4.3.3), but it is worth mentioning that even when the environmental strategy is defined by an specific use, decisions taken in the design stage provide space or opportunity for the building to adopt a different strategy compatible with different uses in order to extend the life of the building before total obsolescence and demolition.

19 | P a g e

3.3 Use of energy 3.3.1 The use of energy in the UK the residential data According to the national statistics the energy use in the domestic sector in the UK is still dominated by the energy used on space heating (57%), followed by water heating (23%), lighting and appliances (15.9%) and cooking (2.9%).

When compared with previous decades the data shows a reduction in the energy used per household (more efficient homes) but an increment in the number of households (more consumption per person).

The main factor in the increase of energy consumption per person is the trend towards single person households. Two persons in a single household will require less energy than the same two persons in two different households, where the appliances and the consumption per person will be increased. Factors like the increment on the number of appliances per household and the increment in the number of lighting appliances have also helped to raise the consumption of energy per person (Department of trade and industry/national statistics, 2010).

2.50

Tonnes of oil equivalent

2.00

1.50

1.00

0.50

0.00 1960

1970

1980

household

1990

2000

2010

2020

person

Figure 3-11 Energy consumption per household and per person -after (Department of trade and industry/national statistics, 2010)

This trend toward small households is almost impossible to overcome trough regulations (Boardman, et al., 2005). This means that the houses need to be even more efficient, but also that a change in the behaviour of the user needs to be addressed to minimize the consumption.

The need for smaller households can be seen also as an opportunity. The flat typology is inherently more efficient in energy consumption due to its lower exposed envelope (YANNAS, 1994) and offers the possibility of promote some 20 | P a g e

communal services displacing it out of the households. The trend on the reduction on the energy used in cooking in the UK (Department of trade and industry/national statistics, 2010) can be indicative of a trend among the users in displacing activities out of the dwelling when this represents time economy.

The possibility of displacing services such as laundry spaces can turn around the situation of many flats when sharing services with other flats. This thought in a bigger scale, could lead to a higher level of energy efficiency. It is also worth considering that another advantage of the flat typology buildings is the possibility of higher efficiencies in energy in space and water heating trough the implementation of centralized systems (Boardman, et al., 2005) as well as the use of renewable sources of energy for water heating.

3.3.2 Massive wood construction and the provision of thermal comfort The purpose of this chapter is to show some distinct characteristics of the massive wood construction system that will be used within the environmental strategies in the provision of comfort by passive means in the architectural application stage.

3. 3 .2 . 1 Ai r t i gh t n es s a nd p re f a br ic a t io n The heat losses through infiltration can explain a large proportion of the heat losses in a building. Improving air tightness can be done without a high additional economical investment (Bell M. , 2006) 3

2

The 2005 Building Regulations establish a value of fabric permeability of 7m h/m @ 50 Pa (cubic meters per hour over square meter of space envelope at a pressure 3 2 of 50 Pa) The CIBSE in addition determines values of 5m h/m @ 50 Pa as “tight”, 3 2 and values of 3.5 m h/m @ 50Pa as “very tight” (CIBSE, 2006) The conversion of those values to infiltration rates at atmospheric pressure differ between building types and heights, meaning that air permeability established by regulations will imply in practice higher infiltration rates for a flat than for a two story house.

The building research establishment BRE in guidance for air tightness (Jaggs & Scivyer, 2006) recommends as strategy for achieving low infiltration rates the Definition of the primary air barrier from a design stage and the adequate detailing on possible gaps in the envelope Study and monitoring on different cases shows that the most common paths for infiltration are gaps around service penetrations through the external walls, floors and ceiling; poorly fitted and draught sealed doors, windows and loft hatch; junction between door/window frame and plasterboard dry lining; and gaps between the upper floor and the external walls. These leakage paths rendered the designed air barrier ineffective” (Bell, Johnson, Miles-Shenton, & Wingfiled, 2007) After comparing results achieved in the permeability test and strategy used, they also affirm that the most robust strategies are: a) Reduce the shape complexity of the primary air barrier. b) Design that ensure the continuity and detailing on site of the air barrier c) On site continuous feedback and guidance, also the author affirms that this is difficult to achieve unless is incorporated on the quality checks and standards used on site.

For these reasons prefabricated houses can achieve low values of air infiltration as the control of gaps between elements could been assessed on factory and quality checked (see Case studies Calewen and Acharacle primary school) When joints are necessary on site, its detailing should be simple.

21 | P a g e

In massive wood construction made of glued elements, the panels itself constitute the vapour barrier and an air tight barrier when the joints are carefully sealed (Ross, Downes, & Lawrence, 2009) and if exposed towards the interior the wood acts as a regulator of the water content of the air (Berge, 2009). In the Brettstapel solutions, because of its scope of plank shrinking along time, the air barrier should be completed by the use of other element different than the massive panels.

Nevertheless, very low air permeability has been achieved with this construction technique. (Bridgestock, Foster, & Henderson, 2010) Ventilation: The provision of ventilation for winter is part of the air tightness strategy.

In airtight buildings the amount of air entering the dwelling via infiltration is reduced below the minimum provision for human health. The need of purposeprovide apertures for ventilation is critical for occupants health and pollutant dissipation. Thus the provision of background ventilation is necessary; this is usually achieved by means of trickle ventilators.

Trickle ventilators reduce the incidence of odour problems and condensation without causing significant increase on energy consumption, but during periods of high pollutant generation the ventilation provided by the trickle ventilators is inadequate. (Edwards, 2005) The same author also affirms that passive stack ventilation (PSV) used in conjunction with the ventilators can provide adequate ventilation rates for the moments of high pollution (in residential use mainly water vapour) Comparison made between airtight and leaky dwellings in relation to the performance of PSV showed that in airtight buildings the ventilation rates achievements were low unless the windows were open (Edwards, 2005).This point out the need of bigger areas for ventilators providing different ventilation rates for different internal conditions.

Another observation made by Edwards was in relation with the risk of over ventilation and the need of some type of control for coupling and decoupling the PSV ducts. This can be done by the use of humidity sensible ceiling terminals activated by the same room humidity (these devices are mechanically activated by sensible materials and requires no energy to operate).

Other considerations that can be taken are: avoiding bending in the ducts, the use of duct diameters below 80mm for bathrooms and 125mm for kitchens and roof top terminals located at least 50 cm above the height of the roof ridge (Edwards, 2005).

3. 3 .2 . 2 In su l a ti on fr o m W as t e A good possibility provide by the wood is the insulation made of wood shavings or sand dust from the manufacturing processes, this has two impacts, re use of some of the waste and the provision of low cost insulation with all the good qualities of recycling value and low embodied energy attributed to the wood.

This provision of low const insulation implies that the limiting factor in the u-values of the walls is the thickness necessary and not the cost what limits the insulation levels.

The conductivity achieved depends on how compressed are the shavings, conductivities of 0.045 W/m K can be achieved (Berge, 2009) The use of external insulation is advisable as the wood panels provide thermal mass towards the interior, also because the external layer of insulation can contribute to the airtightness of the building (Szokolay & Zold, 1997)

22 | P a g e

3. 3 .2 . 3 Wo od ’ s th er m al m a ss The thermal inertia is defined as the “buildings overall capacity to store and release heat.” (Yannas, 2000) The same author affirms that buildings with low thermal inertia will tend to follow the fluctuation in internal temperature caused by solar radiation and internal heat gains, while buildings with high thermal inertia will tend to have more constant temperatures.

In the UK the summer temperatures are usually within the comfort range, and rarely rise above 30C. Nevertheless predictions for climate change (Hacker, Belcher, & Connell, 2005) affirm that peaks in summer temperature above 30C will be more common (under a medium – high emissions scenario) in 2050.

Those peak days when the external temperature exceeds the comfort threshold, the insulation of the closed fabric can restrict the access of heat into the building, but the internal heat gains can raise the temperature inside. Provision of thermal mass can store heat excess to be released later through night ventilation when external temperatures drop Massive wood buildings can offer mass to the building as it uses elements of thicknesses around 100mm. To have an idea of how much storage is possible in solid wood compared with concrete, its physical properties can be analysed according to terminology and calculations proposed for (Yannas, 2000) (See Table 10-2) The physical properties of the wood are extracted from technical information from a provider (KLH UK) Specific heat: 0.44Wh/Kg K 3 Density: 400Kg/m

The specific heat of the spruce panels is 0.44Wh/Kg K meaning that 0.44 Wh are required to raise the temperature of 1kg by 1 degree Kelvin this also represents the energy stored by the material.

3 The massive wood’s density is 400 kg/m . This means that in 1 cubic meter can be stored 400 times 0.44Wh for each degree of increment in the temperature.

This product (density * specific heat) is called volumetric heat capacity, that in this case is equivalent to 0.18 kWh/m3K When a square meter of wall with 10 cm thickness is analysed, for example 1m*1m*0.1m (0.1 m3 in volume), the heat storage per square meter (of 0.1m 2 thickness) is 0.02 KWh/m 3 The same calculation done for concrete with a 2100 Kg/m density and specific heat of 0.23 Wh/Kg K is equivalent to 0.05KWh/m2.

The heat capacity of a square meter (0.1 m thick) of concrete of such density is roughly 2.7 times the storage capacity of a square meter of wood with the same thickness; this means that 2.7 times more area of exposed thermal mass is required to achieve an equivalent thermal performance between the two materials (See Figure 3-12).

Commonly constructions in massive wood use the same massive material in partitions due to its load bearing function. On the contrary, concrete structures use lightweight partitions: this can equal the amount of thermal mass in both structures.

Another difference between wood and concrete is the time that takes to the heat to reach the internal layers of the material, as the conductivity of the wood is lower this time is longer(see Figure 10-1)

23 | P a g e

Storage in 1m2 (10cm thick) 0.60

0.50

KW h/m2 (of 10 cm thickness)

0.40

0.30

0.20

0.10

0.00

1

2

3

4

5

6

7

8

9

10

Massive wood KWh 0.02

0.04

0.05

0.07

0.09

0.11

0.12

0.14

0.16

0.18

CONCRETE KWh

0.05

0.10

0.14

0.19

0.24

0.29

0.34

0.39

0.43

0.48

brick work KWh

0.04

0.07

0.11

0.15

0.19

0.22

0.26

0.30

0.34

0.37

Temperature rise C Figure 3-12 Comparative of stored energy by increment of temperature –after (Yannas, 2000) (KLH UK)

24 | P a g e

4 Context and precedents 4.1 Context and climate Winter: UK climate is characterized by the variability of the cloud cover (Yannas) during the seasons as well as during days. During the winter period some overcast days have neglectible values of solar radiation alternated with sunny days with higer values (see Figure 4-4) Due to the frequence of overcast periods with low solar radiation , the control of losses trough the building fabric becomes more important than maximizing the area of windows for solar access. This specially from the windows that are the weaker point of the envelope.

Summer: In summer average days external temperatures are always on the lower side of the comfort band. This means that buildings can be easily cooled down through ventilation. When solar radiation and internal gains are properly adressed mechanical coolling is thus unnesesary (YANNAS, 1994). In special hot summer days, external temperatures raise above the comfort treshold making impossible the dissipation of heat trough ventilation. In such situations, strategies as night ventilation of well insulated buildings with thermal storage capacity can improve the comfort conditions.

Climate change predictions (Hacker, Belcher, & Connell, 2005) foresee a raise in the overal temperatures specially during the summer (see Figure 4-1), as well as the frequency occurence of hot peaks above 30C. (See Figure 4-3)

Temperature C

Even when during average days of the summer, day ventilation will provide an effective measure to disipate the unwanted heat the occurence of hot peak days will impose the use of night ventilation.

25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5

2005 C 2050 C 2100 C

J

F

M

A

M

J

J

A

S

O

N

D

Figure 4-1 Mean temperature London present and predictions for 2050 and 2100 meteonorm 6.0

25 | P a g e

°C

DRY BULB TEMPERATURE - London, [NoWhere]

1st January to 31st December

°C

40

40

30

30

20

20

10

10

0

0

-10

-10 14th

Jan

28th Feb

14th

28th Mar

14th

28th Apr

14th

28th May

14th

28th Jun

°C

14th

28th Jul

14th

28th Aug

14th

28th Sep

14th

28th Oct

14th

28th Nov

14th

28th Dec

14th

28th

DAILY CONDITIONS - 1st January (1)

W/ m²

Figure 4-2 London dry bulb temperatures- 2005 –Meteonorm 6.0

°C

40

1.0k

30

0.8k

20

DRY BULB TEMPERATURE - London,

1st January to 31st December

10

40

30

0.6k °C 0.4k

LEGEND

40

Temperature Rel.Humidity Wind Speed

Direct Solar Diffuse Solar Cloud Cover

0

0.2k

-10

2

4

6

8

10

12

14

16

18

20

22

24

30 0.0k

20

20

10

10

0

0

-10

-10 14th

Jan

28th Feb

14th

28th Mar

14th

28th Apr

14th

28th May

14th

28th Jun

°C

14th

28th Jul

14th

28th Aug

14th

28th Sep

14th

28th Oct

14th

28th Nov

14th

28th Dec

14th

28th

DAILY CONDITIONS - 1st January (1)

W/ m²

Figure 4-3 London dry bulb temperatures- Prediction for 2100 - Meteonorm 6.0 40

1.0k

30 January-total daily radiation on vertical plane -facing south

Wh/m2

4000 3500 3000 LEGEND 2500 Temperature 2000 Rel.Humidity Wind1500 Speed 1000 500 0

Direct Solar Diffuse Solar Cloud Cover

0.8k

20

0.6k

10

0.4k

0

0.2k

-10

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 DAY Figure 4-4 Daily solar radiation o a vertical plane (south) during the month of January – after Meteonorm 6.0

26 | P a g e

22

24

0.0k

4.2 Precedents and fieldwork The case studies were chosen intending to evidence the thermal performance associated with timber construction and prefabrication. Also, how performance could be affected by other factors related to the construction process.

For these reasons the cases are divided in two general groups; the first two cases where monitored while the others provide information related to construction and logistic issues.

The first monitored case study is Calewen house. Due to the existence of information about its good thermal performance and air tightness, the interest lies in the lack of information related with its summer performance. Monitoring was done during the hot days of July which offered the possibility of being compared with the second monitored case: the office in Milton Keynes built in massive wood construction.

The second group of case studies, as mentioned before, illustrate detailing and logistics in the construction process of massive wood construction.

27 | P a g e

4.2.1 Calewen

Figure 4-5 Calewen houses- Milton Keynes

Figure 4-6 Ground floor plan (YANNAS, 1994)

4. 2 .1 . 1 Bu il d i ng d es cr ip ti o n

28 | P a g e

Calewen is a group of semi-detached houses in Milton Keynes, UK. The houses are built in prefabricated super insulated panels (SIP) which is a type of construction with low energy consumption in space heating: 10KW hour/m2. The low consumption of the building seems to be associated with two factors: the insulation levels and the controled ventilation with an airtight envelope and mechanical ventilation system (pre-heating and heat recovery) (YANNAS, 1994).

The insulation of the envelope achieved levels of insulation for walls of u-value 0.2 W/m2 k, for the roof 0.11 W/m2 k, and triple glazed windows with u-values of 1.44 W/m2 k. A small window floor ratio is used 13%, providing a lower mean u-value for the house’s envelope with all the windows oriented east-west.

The houses are still mentioned among the most airtight buildings in the UK : their air permeability is 1.47 ac/h @50Pa (Bell, Johnson, Miles-Shenton, & Wingfiled, 2007). The ventilation is moderated by a mechanical system with heat recovery and air pre-heating.

The small amount of appertures as well as its orientation (west-east) implies modest solar gains in winter, and bigger solar gains in summer as the houses don’t provided (nor the users did) shading for the west windows.

A total of two houses were visited , its occupants interviewed, and the internal temperatures were measured in the two levels of one of the houses during 1 week on summer.

4. 2 .1 . 2 Inh a bi t a nt s i n te r vi ew : Winter: The inhabitants reported satisfactory internal conditions in winter. The occupant reported that one of the most noted advantages during winter was the quick response to the heating system. This due to the low thermal inertia of the building fabric (the only one massive element is the ground slab and is covered by a carpet) Despite the small amout of window area, the daylight levels were also perceived as satisfactory even for the occupant that works at home. Problems related with noise from the fans of the ventilation system were reported.

Summer: Conditions in the dwelling evidence contradictory reports for different houses. While one of the houses was running with Air conditioning system, the other was free running air with a high level of aceptance of the occupant. When asked about the reasons for instaling the AC appliance the user answered that the ventilation system provided by the house was not blowing enough fresh air, implying that the user was expecting that the mechanical ventilation acomplished the mission to provide fresh air in summer.

The ventilation of the free running house was done through opening of the windows in the ground floor towards the internal courtyard and in both sides in the first floor when occupied, but the windows are keept closed for security reasons when the house is left alone.

Durability and quality: Another important question made to the occupants was about the durability and quality of the construction. Occupants from both houses reported to be satisfied. A quick inspection of the building shows the houses are maintained in good conditions. The users report little and unexpensive maintenace such as the painting each 8 years and montly cleaning of the facade surfaces.

The noise of the fans providing the mechanical ventilation were reported as a source of anoyance.

29 | P a g e

4. 2 .1 . 3 M on i to r in g : The house chosen to be monitored was the one that runs without AC (6 to 19 July 2010) . This monitoring process was done at the same time that the secod case study, “The office”, was monitored measuring internal temperatures.

The monitored period presented average summer days with external temperatures peaks at 21- 26 centigrades, and a period of two hot peaks maximum external temperatures during the day of 28 and 31 centigrades.

Internal temperatures showed to be below the calculated comfort limit for summer during the average summeer day,s but during the two hottest days the internal temperatures raised to 32-34 Centigrades (See Figure 4-9,Figure 4-10) User operation during monitored period : During summer the mechanical ventilation is running all the time while day and night without preheating the air. When the house is not occupied the windows remained closed and the mechanical ventilation is still on. At night the occupants 3 sleep with the windows of the bedroom open .

The overheating presented on the house, together with the fact that the internal temperatures were consistently higher than those in the other monitored case “the office”, could be caused by several factors: The lack of solar control. The house is exposed to the solar radiation in the summer afternoons which raises the internal temperature as the house is very sensitive to heat gains (see Figure 4-7,Figure 4-8.)

The ventilation mode used by the occupants. During the hot days when the house is closed and the hot external air is dragged into the house by the mechanical ventilation system warms up the house; and good insulation levels keeps it warm.

As the windows are not provided with means of secure ventilation (other than opening the windows) the always running mechanical ventilation seems to the users as the only alternative.

The low thermal capacity of the structure (that provides the quick response to the heating system in winter) makes the house sensitive to the heat input by solar gains (not controlled) and the ones provided by ventilation in the hot days.

The occupation of the house is low (ussuallyone person in the day and two in the night ). More intense occupation rates could drive to higher temperatures

3

Transcription of the questionnaire answered by the occupant Tony Mc Guinness after the monitoring Did you open the windows in summer?

We usually sleep with the upstairs windows open on warm wind free summer nights.

Did you turn on the mechanical ventilation?

We leave the mechanical ventilation running all the time.

Did you turn on the heating in the night?

No, We turn the heating thermostat down to a lower level in the summer Did you close the house and turn on the mechanical ventilation?

If we leave the house for a long time we sometimes close all the windows, the mechanical ventilation is running all the time. (Mc Guiness, 2010)

30 | P a g e

Figure 4-7 Kitchen- sun patch summer afternoon

Figure 4-8 dining room – sun patch summer afternoon.

As a conclusion from this case study, it can be said that the quick response of the building fabric to the internal gains and the controled losses through ventilation and

31 | P a g e

through the building fabric explains the low heating energy consumption reported in winter.

The same characteristics can lead to overheating in summer as no solar control is provided. Mechanical ventilation is espected by the occuapnts to work all the time, not taking full advantage of the cooler exterior air when is present and dragging it into the interior hot air when is not wanted in the hot peak days.

Windows in the ground floor are not used by security reasons. If secure ventilation means existed, summer ventilation strategy would be improved.

As an important conclusion, and relevant to the house equipped with AC undesrtood by the user as an improvement of the mechanical ventilation performance, the mechanical ventilation system can create on the user the expectation of provision of comfort without interaction with the exterior.

Calewen and the office - Internal temperatures monitored during 6-8 July 2010 30.00 °C 29.00 °C 28.00 °C 27.00 °C 26.00 °C 25.00 °C 24.00 °C 23.00 °C 22.00 °C 21.00 °C 20.00 °C 19.00 °C 18.00 °C 17.00 °C 16.00 °C 15.00 °C 14.00 °C 13.00 °C 12.00 °C 11.00 °C 10.00 °C 00

06

12

18

CALEWEN GROOUND FLOOR

00

06

12

18

CALEWEN FIRST FLOOR

00

06

THE OFFICE

Figure 4-9 Internal Temperatures monitored- external temperatures after (Weather underground)

32 | P a g e

12

18

EXTERNAL

Calewen and the office ,Internal temperatures monitored during 6-19 JULY 2010 36.00 °C 35.00 °C 34.00 °C 33.00 °C 32.00 °C 31.00 °C 30.00 °C 29.00 °C 28.00 °C 27.00 °C 26.00 °C 25.00 °C 24.00 °C 23.00 °C 22.00 °C 21.00 °C 20.00 °C 19.00 °C 18.00 °C 17.00 °C 16.00 °C 15.00 °C 14.00 °C 13.00 °C 12.00 °C 11.00 °C 10.00 °C 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 CALEWEN GROOUND FLOOR

CALEWEN FIRST FLOOR

THE OFFICE

Series4

Figure 4-10 Internal Temperatures monitored- external temperatures after (Weather underground)

33 | P a g e

4.2.2 The office

Figure 4- The office, Milton Keynes –David Grindley architects

Figure 4-11 Axonometric view – Source: David Grindley architects

34 | P a g e

4. 2 .2 . 1 Bu il d i ng d es cr ip ti o n: ‘The office’ is an extension of a terraced house used as work space for an architecture practice. In this case, the building is also expected to be used in the future as a ‘granny extension’. The building, located in Milton Keynes, is made of massive glued spruce panels (cross laminated timber) that were cut to size and arrived to the site ready with openings.

The panels are exposed to the interior with no additional finishing but fire retardant treatment. The insulation is external, a breathable natural rubber is used as water proof membrane and the exterior cladding is made of untreated lash.

The building has small opening towards the south and high windows are provided for daylight and ventilation. Additional secure lower apertures are provided for ventilation purposes.

Actually the building is occupied by 3 people working on computers in an office based schedule.

4. 2 .2 . 2 Occu p a n ts i n te r vi e w Interviews with the occupants reported their satisfaction with the building performance in thermal behaviour, daylight, fresh air provision etc. both in winter and summer.

And interesting point to highlight to mention is the ventilation strategy used in the summer. The interviewed occupant reported that by trying different strategies in the hot days the most effective proved to be closing windows during the day and providing ventilation during the night (Grindley, 2010).

This could be indicative of the role of the thermal mass provided by the exposed massive wood in the building allowing day storage of heat to be released at night.

4. 2 .2 . 3 M on i to r in g The building was monitored during the same period in which the Calewen house was monitored: between 6 and 19 of July.

Compared to the Calewen house thermal performance during the same period the building maintain temperatures 2 to 4 centigrade lower during the average days, and during the hot peaks of external temperatures, the internal temperature remained under 27 degrees.

The temperature also showed a more stable behaviour being less reactive to the external changes and internal heat inputs.

This behaviour of the building could be the result of several factors: Solar access: The building’s appertures are mainly towards the north. The ones facing south are very small.

Ventilation: The building has very controlable and secure means of ventilation, making possible to ventilate when the building is unoccupied (in the nights) without compromising its security.

The ventilations provided for ventilation are distributed both horizontaly and vertically, thus taking advantage of the difference of wind pressure and the stack effect in the interior.

Thermal mass: The monitored temperatures showed that the buiding has some thermal storage capacity by its reaction to internal and external heat inputs.

This is indicative of the possibility through the combination of strategies to cope with hot days in a wooden structure. It also provides insights of the possible use of the thermal mass in the massive wood buildings without the need of additional elements as brick, concrete or phase change materials.

35 | P a g e

This is relevant in the scenario of weather with higher temperatures and more frequent hot peaks due to the climate change phenomena. Also in the scenario of possible changes of use trough the building’s life.

Figure 4-12 Internal view- exposed timber panels-upper and lower ventilation openings

Figure 4-13 Ventilation opening with security louvers ventilation when unoccupied

36 | P a g e

4.2.3 Stadthaus

Figure 4-14 Stadhaus, London (Thompson, 2009)

Stadthaus is a 9 storey building located in London. The structure is made completely of massive timber (cross laminated panels) whit the exception of the ground floor which is built in concrete structure.

The building proves the possibility of use of massive timber in multi-storey applications (above 6 storeys) while complies whit the building regulations in matters of structural behaviour, fire security and noise insulation. The fire resistance is achieved through additional layers of plaster and the sound is achieved through additional layers on the slabs (see Figure 4-14) The construction process is well documented and shows the advantages of prefabricated construction: structural panels reached the construction site with precise measures and window and service openings (See Figure 4-18) . The erection of the structure required only four people; there was no need for a tower crane and the panels were lifted using a mobile crane. The material requires little storage space on site (Thompson, 2009).

Time savings were also recorded, as the building was also studied to be built on concrete. The time used finishing the building (49 weeks) was lower than the programmed for the concrete alternative (72 weeks) of which only 27 days were used erecting the structure. This also was object of comparison for the weight of the 37 | P a g e

structure; the lower density of the wood (480 kg/m3) compared to concrete 3 (2400kg/m ) results in a reduction of the weight of the structure of 75% on the total weight of the structure (wood 300tonnes and concrete 1200tonnes) (See Figure 4-15) The environmental strategy of the project focuses on the reduction of carbon emissions associated whit its construction, and the low embodied energy of the structure.

Due to the volume of wood used in its structure, this building compensates the CO2 emitted in the transport of the material from Austria leaving a positive balance of 187 ton of Carbon sequestrated. The energy used in the production of the panels is produced in the factory through waste from the wood. Nevertheless no figures have been published on efficiency on energy consumption (Thompson, 2009).

The panels are recyclable as material or as biomass in the production of energy. The adhesive used (polyurethane) in the production of the panels requires no special burning process, nevertheless it is not the most common in the production of cross laminated timber that usually contains formaldehyde and other toxic chemicals.

(Thompson, 2009) The structural design on the building requires that all internal partitions work as load bearing elements (See Figure 4-17), solution that diminishes the adaptability to changes of the building; due to the impossibility of changes in the internal layout.

Nevertheless this is not an unavoidable characteristic of the construction technique but a lack of integration of this parameter in the design process.

The thermal mass available on the massive timber is covered by plaster boards and thus not used. This highlights the convenience of a different approach to fire spread such as sprinkles or fire retardant impregnation.

Figure 4-15 2009)

38 | P a g e

Comparative weight of concrete and massive wood structure (Thompson,

Figure 4-16 Typical details – external wall and lift-flat wall

Figure 4-17 Typical plan- Structural wood panels shaded green

39 | P a g e

Figure 4-18 Wood panels and connectors

40 | P a g e

4.2.4 Acharacle primary school - Argyll, Scotland

Figure 4-19 Acharacle primary school, Argyll, Scotland (TRADA, 2010)

The Acharacle primary school is made completely of massive wood making it the first building in Brettstapel technology in the UK (Bridgestock, Foster, & Henderson, 2010) The prefabricated panels were supplied by a German factory due to the fact that there are not suppliers of Brettstapel in the UK; nevertheless the potential for the use of local wood is acknowledged (TRADA, 2010) The panels are composed by the structural massive panel and 280mm of wood fibre insulation, to guarantee air tightness. Additional timber sheathing is provided both sides of the insulation; the external finish is untreated wood cladding (Figure 4-22,Figure 4-20) The measurements made for air tightness resulted in a very low tested air permeability of 0.27m3/m2/hr@50Pa. The sealing of gaps where carefully assessed through design and services were placed far from the exterior envelope (TRADA, 2 2 2010). The U-values of walls and roof are 0.128W/m k and for floors 0.098 W/m k making the project’s very thick walls (around 38 cm) The massive wood is exposed towards the interior (Figure 4-21) while the insulation is external. The fire structural resistance relies on the charring rate of the wood, and a sprinkler system provides additional safety limiting the flame spread by the wood

41 | P a g e

Figure 4-20 prefabricated panel

Figure 4-21 Interior view

42 | P a g e

Figure 4-22 Envelope detail

43 | P a g e

5 Analytic work Due to the obstruction of solar radiation in urban sites, a bigger reliance on internal gains and control of the heat losses, both, through the building fabric and ventilation, become more important and thus the base of this research project’s environmental strategy.

The urban infill typology results in compact shapes as well as in low ratios of exposed areas. The proposed construction, prefabricated massive wood technology provides good levels of insulation and air tightness. The analytic work is proposed in order to test this strategy.

5.1 Benchmark: The criterion to assess the performance of the proposal is based on the review of information related to cases using a similar strategy based on air tightness. This strategy is related to the lower consumption cases in the index on energy consumption of dwellings in the UK by 1994. (YANNAS, 1994) The lowest recorded cases were detached and semi-detached houses, among them, Calewen. (See case studies) whose energy consumption is around 10KWh / m2 per year.

This is indicative for multi-storey compact dwelling types of similar air tightness and insulation levels; this performance should be improved.

Another standard with a similar approach is the Passivhaus that relies on low values of air infiltration: control of heat losses through the building fabric, heating provided by pre-heated ventilation (mechanical) and heat recovery. The bench mark value for the energy consumption of the Passivhaus standard is 15 KWh/m2 per year or less.

This is related to the impossibility of providing heating via pre-heating ventilation for higher consumptions. (PassivHaus Institut Darmstadt) This standard has been tested in its adaptation to the UK weather with modifications as controlled natural ventilation and summer solar control ( (Ford, Schiano-Phan, & Zhongcheng, 2007) Then, values below 10KWh/m2 per year are the expected performance under optimum conditions, and values below 15KWh/m2 per year are expected from low occupancies or higher comfort expectations of the occupants.

5.2 Comfort The comfort threshold is calculated based on the formula Tn = 17.8 + 0.31 • Tm (Auliciems & Szokolay, 2007) that takes into account adaptation to seasonal variations of external temperature. Based on this criteria comfort bands are calculated with different weather files for actual conditions and future climate change scenarios (data from Meteonorm 6.0), taking into account the effect of the change of the climate in the perception of comfort of the users (See Figure 5-1).

The resulting comfort band is used to assess the thermal simulations as trigger for o the heating loads that in the actual weather scenario the limit is 18C . The upper o. limit for cooling is 28 C This value is used to assess the behaviour of the building in hot periods as the use of cooling appliances is not contemplated. Additional to this comfort band, the occurrences of hotter days on summer are understood as tolerable under the criteria of adaptive opportunity.

It is worth highlighting that dwellings offer more adaptive opportunities than other spaces taking into consideration the possibility to change level of clothing and level of activity, the availability of cold and hot drinks, plus the control over aspects of the building as ventilation and shading (CIBSE, 2006) Those adaptive opportunities can be of a personal nature or provided by the building, and can together extend the upper limit of the comfort band up to 8C. (Baker, REVIVAL technical monogram 2:Adaptive thermal comfort and controls for building refurbishment) 44 | P a g e

2010 35.0 34.0 33.0 32.0 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0

J

F

M

A

neutral

M

J

upper

J

A

S

lower

O

N

D

external mean

2050 35.0 34.0 33.0 32.0 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0

J

F

M

A

neutral

M

J

upper

J

A

S

lower

O

N

D

external mean

2100 35.0 34.0 33.0 32.0 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0

J

F neutral

M

A

M upper

J

J

A

lower

S

O

N

D

external mean

Figure 5-1 Comfort band and external mean temperatures - after (Auliciems & Szokolay, 2007) and meteonorm 6.0

45 | P a g e

5.3 Environmental strategies 5.3.1 Winter: Due to the nature of dense urban context the main challenge in the provision of heating by passive means is the absence of solar gains. Two main causes are related with heat losses in a building, and will be addressed in the design of the project: Ventilation and infiltration: The aim is to minimize the uncontrolled occurrence of infiltration through the building fabric as the ventilation is necessary for the occupants.

Control over the infiltration rates could be very effective on the reduction of heating loads but poses a challenge for the provision of natural ventilation.

The losses through the buildings envelope: In this case the area of exposed envelope and the conductivity of the envelope itself are the main factors to take into consideration.

Exposure: urban sites, flat typology, sharing slabs and in attached configurations; resulting in very compact shapes.

Envelope conductivity: The mayor opportunity to envelope improving is the window insulation.

5.3.2 Summer: Ventilation: In summer external temperatures are usually in or below the comfort range, thus there are in most of the day’s potential for dissipating heat by ventilation.

Shading: The solar radiation can raise the internal temperature when coinciding with peaks of internal gains, thus the provision of shading is advisable.

Thermal mass: When the external temperatures are above the comfort limit it is recommended to close the dwelling allowing the minimum ventilation and relying on the thermal mass to sink the heat excess until the external temperature drops and the heat could be dissipated through ventilation.

5.4 Thermal analysis 5.4.1 Material characteristics Test description: The test is done to compare the thermal behaviour of the massive timber with other types of construction.

Four models were tested as a mean for comparison: a light weight structure equivalent to timber frame construction, massive timber construction with and without plaster boards on the walls, and finally a cavity wall construction.

To make the massive timber and cavity wall constructions comparable, the internal partitions on the massive timber model are assumed as massive (as occurs in the Stadthaus case) while in the cavity wall one the internal partitions are modelled in plaster.

46 | P a g e

Model description: U-value of walls is 0.35Wkm2 the window u-value is 2.2 Wkm2 the infiltration rate is 0.25Ach, the ventilation is equivalent to 30m3 per person.

The floor area of the dwelling is 75 m2, the volume 225 m3 and the exposed area of the envelope is equivalent to the 40% of the floor area.

The thermostat is set to 18 C for heating and 28C for cooling.

The variable parameters are the type of construction and the WFR. Shading is applied to the windows during the summer period.

Timber frame:  External walls (from inside to outside): Plasterboard, insulation, sheathing panel.  The interior partitions: Plasterboard air gap and plasterboard.  The slabs (from ceiling to floor): Plasterboard, air gap, wood panel, screed, and wood finish.

Massive wood panels, plastered faces (as Stadthaus): 4  External walls (from inside to outside): plasterboard, massive wood panel , insulation (no cladding is contemplated).  Interior partitions: plasterboard, massive timber panel and plasterboard.  The slabs (from ceiling to floor): plasterboard, air gap, massive wood panel, screed, and wood finish.

Massive wood panels exposed faces:  External walls (from inside to outside): massive wood panel, insulation (no cladding is contemplated).  Internal partitions: exposed massive timber panels.  Slabs (ceiling to floor: of massive wood panel, insulation, and wood finish.

Medium weight Cavity wall:  External walls (from inside to outside): rendering, brick, insulation, cavity, insulation.  Internal partitions: plasterboard, air gap, and plasterboard.  The slabs (from ceiling to floor): concrete, screed, and wood finish.

4

The Thermal properties of the massive timber are modelled in TAS EDSL with information for density and specific heat provided by (KLH UK), as seen on chapter 3.3.2.3 47 | P a g e

12.00 11.00 10.00 9.00 KWh/m2

8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 WFR 15 %

WFR 20%

WFR 25%

WFR 30%

timber frame Heating Plastered Cross laminated panels Heating Medium weight (brick concrete) Heating Exposed cross laminated panels Heating timber frame Cooling Exposed cross laminated panels Cooling Figure 5-2 Heating and cooling loads for different constructions - TAS EDSL

Test results: The Test compares the impact of the construction materials in the heating and cooling loads for the building (See Figure 5-2).

The exposed massive wood and the Cavity wall performed in a similar way and showed some reductions (around 19%) on heating loads in relation to the timber frame construction; this effect was much lower when the massive wood was covered by plaster (see Figure 5-2). o The higher cooling loads (thermostat set on 28C ) resulting in the timber frame structure occurred mostly on sunny days in winter and in the peak hot days in summer.

The result suggests that massive wood buildings can cope with more heat stimulus for instance higher fenestration areas or higher internal gains than the light weight buildings and that those results are comparable to those of medium weight construction when extra area is provided by the massive internal partitions.

The same models were tested free running to compare internal temperatures.

During winter in sunny days the massive constructions prevented overheating (as o shading is not applied at this period of the time temperature rises to 28C in lightweight model) (See Figure 5-4), and during cloudy days, the massive constructions presented slightly higher temperatures product of the release of the stored energy (Figure 5-3). This cumulative effect explains the lower overall heating loads in the massive constructions.

During summer, in average days, when the external temperatures were lower than the internal, the temperatures in the interior of the spaces presents no difference o except for slightly higher (by around 1C ) temperatures at night (Figure 5-5), when the external are above the comfort band the building is closed (simulating user control) ;the massive constructions shown lower temperatures(See Figure 5-6)

48 | P a g e

Winter January 17 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3

1

0.75

0.5

0.25

0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Cloud Cover (0-1)

CLT EXPOSED

CLT AS STADHAUS

MEDUM WEIGHT

TIMBER FRAME

External Temperature (°C)

Figure 5-3 Winter Overcast day - free running temperatures –TAS EDSL/METEONORM 6.0

winter January 27th 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3

1

0.75

0.5

0.25

0

Cloud Cover (0-1)

Massive wood (Exposed)

Massive wood (covered)

Cavity wall (medium weight)

Timber frame (light wieght)

External Temperature (°C)

Figure 5-4 winter sunny day - free running temperatures –TAS EDSL/METEONORM 6.0

49 | P a g e

Summer July 15th

ventilation

30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

1

0.75

0.5

0.25

0 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Cloud Cover (0-1)

Massive wood (Exposed)

Massive wood (covered)

Cavity wall (medium weight)

Timber frame (light wieght)

External Temperature (°C)

Figure 5-5 summer average day - free running temperatures –TAS EDSL/METEONORM 6.0

Summer July 21th 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

1

0.75

0.5 Internal gains 0.25

0 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Cloud Cover (0-1)

CLT EXPOSED

CLT AS STADHAUS

MEDUM WEIGHT

TIMBER FRAME

External Temperature (°C)

Figure 5-6 summer hot peak day - free running temperatures –TAS EDSL/METEONORM 6.0

50 | P a g e

5.4.2 Winter performance The main energy consumption objective during winter is the reduction of heating loads while maintaining the conditions of comfort at the interior of the dwelling.

5. 4 .2 . 1 A i r t igh t ne s s: Test description: a model is tested for different values for infiltration; ventilation rates are kept fixed along with the other characteristics of the model.

The definitions of airtight buildings from CIBSE are used (CIBSE, 2006) The simulations are done in the thermal simulation software EDSL TAS ver. 9.1.3.1 Model description: The exposed area is 70% of the floor area.

The ventilation is calculated as 30 m3 per hour per person of occupation.

The internal gains summed up 4840KW/h per year for the whole zone tested.

The U values of the constructions are for walls 0.35 and for windows 2.2 (no floors or roof constructions used) o The thermostat is set on 18 C for heating.

The variable parameter is the infiltration rate expressed in ac/h is calculated from the air permeability definitions on the CIBSE guide and the case study The Acharacle School (experimental value for conversion to normal atmosphere pressure for multistorey constructions 2-6 storey). A table with the conversions used in the test is plotted below (see Table 5-1) Infiltration rates in air changes per hour are calculated for a space of 75 m2 in floor area, a volume of 225 m3 and an envelope of 187m2 and used as the variable parameter.

Table 5-1 infiltration rates calculated in Air changes per hour. After values from (CIBSE, 2006)and (TRADA, 2010)

Envelope area Volume Conversion factor for 2-6 storey (divisor)

10

part L 2005 cibse guide Atight cibse guide A very tight Acharacle school

7 5 3 0.27

m3h at 50Pa m3h at 50Pa m3hat 50Pa m3h at 50Pa m3h at 50Pa

17.30

Infiltration rate ac/h

Rounded value for test: infiltration rate ac/h

1870

108.09

0.48

0.50

1309

75.66

0.34

0.35

935

54.05

0.24

0.25

561

32.43

0.14

0.15

50.49

2.92

0.01

0.01

Note: the envelope value includes all the areas of the perimeter of the heated zone, exposed or not.

51 | P a g e

m2 m3

Air permeability m3/h @ normal pressure

Air permeability m3/h @ 50Pa part L 2002

187.00 225.00

Test results: The results are plotted as percentage of reduction in the heating loads, against the loads resulting from the part L 2005 requirement (See Figure 5-7) The heating loads resulting from the base case are considerably low as consequence of the compact configuration.

The result of reducing infiltration rates from the base case (part L 2005) to the “very airtight” definition (Cibse) result in a reduction in heating loads of the 50%.

Further reduction based on the Acharacle School reported a reduction of the 78% on the heating loads.

Nevertheless is important to mention that the reduction of infiltration rates below the ventilation requirement for the occupants requires special care for the provision of ventilation.

27.00

0.9 0.8

78.05% 22.00

21.83

0.7 0.6

17.00

50.45%

15.40

0.5 0.4

11.37

12.00

0.3

26.17% 7.63

7.00

0.2 0.1

0.00%

3.38

2.00

0 0.5 ach

0.35ach

0.25 ach

0.15 ach

0.01 ach

part L 2002 part L 2005 cibse guide A- cibse guide A- Acharacle (10 m3h @ 50 (7 m3h @ 50 tight very tight (0.27 m3h @ Pa) Pa) (5 m3h @ 50 (3 m3h @ 50 50 Pa) Pa) Pa) heating loads

reduction from part L 2005 %

Figure 5-7 Result from thermal simulation – TAS Edsl version 9.1.3.1

5. 4 .2 . 2 Fa b ri c in su l a ti o n - Ex p os ed bu il d in g e nv el op e a nd w i nd ow t o fl oo r r a t i o: Test description: An array of different combinations of window to floor ratio and ratio of building exposed area over floor area (exposure) is tested for heating loads.

This to identify the possible performance of the building under different configurations and also to figure out whether the solar gains or the overall fabric thermal resistance was dominant factor reducing the heating loads.

The set of values used for the exposure are derived from the compact shapes associated to multi-storey flat typology construction.

52 | P a g e

Model description: The ventilation is calculated as 30 m3 per hour per person of occupation and the infiltration rate is 0.25ac/h The internal gains summed up 4890 KW/h per year for the whole zone tested.

The U values of the constructions are for walls 0.35 and for windows 2.2 (no floors or roof constructions used) The floor area is 75m2 in all cases.

The thermostat is set on 18 Co for heating.

The exposed area /floor area ratio and the window area/floor ratio are the variable parameters (See Figure 5-8)

Figure 5-8 Above: Plan view of the tested models: All models have the same floor area, the red line represents exposed walls the blue one partitions and the grey line represents not exposed/ buffered surfaces. Bottom: Axonometric view zoned areas (in color) for different window to floor ratio and grey areas not zoned.

Results: The result chart (see Table 5-2 heating loads for different exposed envelope/floor ratio and window to floor ratio- building regulations +airtight envelope 0.25 ach) is coloured by ranges of energy consumption: The blue colour shows values over 15 kW h/m2, the purple values between 15 KWh/m2 and 10 KWh/m2, and values below that range are not coloured.

The models were tested based on building regulation insulation values, but with an improved control of infiltration (infiltration rates 0.25 ach). In unobstructed conditions the resulting heating loads proved to be very low (below 20 KWhm2 in all cases) and depending on how compact or obstructed the scheme is, further envelope improvements seems to be unnecessary. Nevertheless those values are tested in an ideal unobstructed scenario: the lack of solar gains due to orientation and obstruction could lead to the need of additional fabric improvement.

53 | P a g e

The results consistently showed reductions of the heating loads for the lower amounts of fenestration even if this implies lesser solar gains. The size of the windows then should be selected based on the provision of daylight.

Further improvement to the thermal resistance of the building envelope and control of the exposed areas are advisable for situations where the solar gains are reduced.

Table 5-2 heating loads for different exposed envelope/floor ratio and window to floor ratio- building regulations +airtight envelope 0.25 ach

WFR 15% WFR 20% WFR 25% WFR 30%

6.8 7.9 9.2 10.4 11.9 8.3 9.4 10.6 11.9 13.4 9.8 10.9 12.2 13.4 14.9 10.8 12.6 13.9 15.1 16.6 exp 40% exp 50% exp 60% exp 70% exp 80%

14.6 16.0 17.5 19.2 exp 100%

5. 4 .2 . 3 Fa b ri c in su l a ti o n -W i nd ow imp r ov em e nt A second run is done with the previous configuration but improving the thermal resistance of the windows by the use of night shutters; as the windows are the most conductive elements on the envelope it’s improving is more effective than the wall improvement (see Figure 5-3) Table 5-3 heating loads for different exposures and WFR building regulations +airtight envelope 0.25 ach after window improvement-(night shutters)

WFR 15% WFR 20% WFR 25% WFR 30%

4.2 5.0 5.9 6.3 exp 40%

4.3 4.9 5.6 6.4 exp 50%

54 | P a g e

5.4 6.0 6.7 7.5 exp 60%

6.5 7.1 7.7 8.5 exp 70%

7.9 8.4 9.0 9.8 exp 80%

10.5 10.9 11.5 12.2 exp 100%

5. 4 .2 . 4 Fa b ri c in su l a ti o n - W al l i ns u l at i on : The test compares wall thickness, U-value, and heating loads obtained in thermal simulation.

The construction used is composed by internal layer of massive wood and external insulation made of wood shavings the conductivity (0.45 W/m K). Values used are proposed (Berge, 2009) from data obtained from a manufacturer Baufritz for the thermal simulation a progression of u-values is used the tested u-values are from 2 2 0.4W/M k to 0.10 W/M k(See Table 10-1).

The results show a consistent reduction of the heating loads proportional to the reduction of the u-value, but the thickness necessary to achieve lower u-values increases at higher rates after u-values around 0.25 W/M2k, making constructions of lower u-values unpractical (See Figure 5-9Figure 5-10)

2

2

0.30 W/m k

0.25 W/m k

2

0.24 W/m k

0.27 m

2

2

0.20 W/m k

2

0.15 W/m k

0.32 m

0.1 W/m

0.4m

0.53 m

Figure 5-9 Plans-Wall thickness and u-value- After (Berge, 2009)

0.6

16

0.55

14 0.53

0.5 0.45 0.4

0.4 0.35

0.35

8 0.3

0.3 0.25 0.2

0.24 0.21

0.23

0.32

6

0.27 0.25

4

0.2 0.15

0.15 0.1 Heating loads (KWh M2)

2 0.1

WALL THICKNESS (m)

0

U VALUE (W/m2 k)

Figure 5-10 Wall insulation, thickness and U-value-After TAS EDSL- (Berge, 2009)

55 | P a g e

10

0.4

KWh /m2 per year

12 meters or W/m2 k

2

0.35 W/m k 2 k W/m k 2k 0.23 W/m

5. 4 .2 . 5 Or ie n t at i on : Test description: The effect of the change in orientation in the heating loads was tested for two different levels of fenestration (WFR 15% and WFR 25%) The results are plotted both in terms of annual heating loads per square meter, and as variation percentage in relation to the south orientation.

This test is done to figure out the effect of the orientation or the solar obstruction in the heating loads achieved in previous test.

Model description: 2 The area of the model is 75m The exposed area is 60% of the floor area (See Figure 5-11) The ventilation is calculated as 30 m3 per hour per person of occupation.

The internal gains summed up 4840KW/h per year for the whole zone tested.

The U values of the constructions are for walls 0.35 and for windows 2.2 (no floors or roof constructions used) o The thermostat is set on 18 C Results: The resulting heating loads are increased by non south orientations by different percentages depending on the WFR: the higher the WFR the more sensitive is the building to the reduction of the solar gains.

Nevertheless the range of performances achieved after the reduction of the infiltration and window improvement (Figure 5-12and Figure 5-13) mean that the heating loads could been kept below 20 KWh/m2 in north orientations when the WFR is kept below 25% and the exposure/floor ratio is also kept close to 100%.

WFR 25% WFR 15%

W f r 2 5

Figure 5-11 Model- Zoned areas in colour- TAS EDSL

% W f r 1 5 %

56 | P a g e

N 20.00 15.00 W

E

10.00 5.00 0.00

SW

SE

S heating load for WFR 25% (KWh/m2 per year) heating load for WFR 15% (KWh/m2 per year) Figure 5-12 Increment on heating loads due to orientation for different window to floor ratio configurations – Heating loads KWh/m2- After TAS EDSL

75.44%

80.00% 70.00% 60.00%

53.19%

48.73%

50.00% 40.00%

38.50%

35.76%

25.95%

30.00%

25.72%

20.00% 18.21%

2.89%

W

SW

0.00%

10.00% 0.00%

S

heating load variation WFR 25% (%)

SE

E

N

heating load variation WFR 15% (%)

Figure 5-13 Increment on heating loads due to orientation for different window to floor ratio configurations – percentage of increment in relation to south orientation (%)- After TAS EDSL

57 | P a g e

5. 4 .2 . 6 Th e r mo s t at se tu p Test description: In order to assess the impact of the occupant expectations of comfort and setup of the thermostat, different thermostat limit temperatures are tested and the resulting heating loads compared. The base case is 18C. Model description: 2 The area of the model is 75m The exposed area is 100% of the floor area.

The ventilation is calculated as 30 m3 per hour per person of occupation.

The internal gains summed up 4840KW/h per year for the whole zone tested.

The U values of the constructions are for walls 0.35 and for windows 2.2 (no floors or roof constructions used) and no night shutters are used. o o The thermostat is set on 18 C for heating in the base case and is increased by 1C up o to 21C Test results: The result show increment on the heating loads; the results are plotted as percentage of increment against the base case (18Cc) (see Figure 5-14) showing that increments on the temperature of use on the dwelling can double the energy consumption.

109.49% 110.00%

35.00

32.25

30.00

90.00%

25.91 25.00 68.30%

20.31

20.00 15.39

70.00% 50.00%

15.00 31.94%

30.00%

10.00

10.00%

5.00 0.00% 0.00

-10.00% 18.00 19.00 heating loads KWh/m2

20.00 21.00 percentage of increment against 18C

Figure 5-14 Increment of heating loads due to thermostat setup –After TAS EDSL

58 | P a g e

5.4.3 Summer 5. 4 .3 . 1 Sh ad in g Test description: the model is tested with and without window shading on summer with the thermostat is off The internal temperatures are plotted along with the cloud cover and the external temperature.

Model description: 2 The area of the model is 75m The internal gains summed up 4600KW/h per year for the whole zone tested.

Test Results: In the absence on shading the internal temperatures reach peaks o. above the 28C Those peaks are inexistent when the windows are shaded.

33

100.00%

32 31

90.00%

30 29

80.00%

28 27

70.00%

26 25

60.00%

24 23

50.00%

22 21

40.00%

20 19

30.00%

18 17

20.00%

16 15

10.00%

14 13 12

0.00%

1

7 13 19 1

7 13 19 1

Cloud Cover (0-1)

7 13 19 1

7 13 19 1

External Temperature (째C)

7 13 19 1 shade on

7 13 19 shade off

Figure 5-15 Effect of shading in internal temperatures in summer -after TAS EDSL, Meteonorm 6.0

59 | P a g e

5. 4 .3 . 2 Ven t il at i on

Test description: The model from previous test is tested for different modes of ventilation, single side with and without vertical distribution of openings an different proportions of opening areas in relation to the floor area (see Figure 5-17).

Results: For the hot peak days in summer the resulting internal temperatures in the simulations were 3Co bellow the external temperatures when shading and ventilation were provided.

The vertical distribution of the apertures produced a significant improvement in the internal temperatures on average days (around 1Co).

Little difference was obtained on the increasing of the openable area above 3% of the floor area and the most noticeable difference was caused by the vertical distribution of the apertures.

32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

1

7

13

19

1

7

13

19

1

7

13

19

1

7

13

19

1

7

13

19

1

7

External Temperature (째C)

total aperture area 3%-upper and lower appertures

total aperture area 5%-upper and lower appertures

total aperture area 3%-single apperture

total aperture area 7%-upper and lower appertures

Figure 5-16 Summer ventilation-After: TAS EDSL

60 | P a g e

13

19

Figure 5-17 Single side ventilation- zoned areas in colour

5. 4 .3 . 3 D if fe r en t u s e - oc cu p a n cy c on d i ti o ns – b u il d i ng ad ap t ab il i t y

Test description: To define strategy to provide adaptability for the spaces the previous model is tested exploring the conditions of the previous residential case under higher occupancies in office schedules.

2 The internal loads used are proposed by CIBSE for office densities of 10m per person (CIBSE, 2006) Different ventilation strategies and opening areas are tested.

Results: Two levels of adaptation of the building seem to be possible: The reuse of the building as it is, for which the openable area was improved to 5% of the floor area and night ventilation strategy was tested.

The retrofitting of the building towards an open plan, for which the use of stacks was tested to assess the amount of areas that should be provided as a prevision measure, as result 5% of the floor area for stack sectional area and equivalent area of openings for inlets As result can be concluded that a 5% area of openings and the equivalent area of vertical stack (for instance on stairs shaft) could provide adaptability to the building for different uses, as offices, even thought in the peak days the comfort band should be expanded by the provision of adaptive opportunities as the temperatures reached 30Co (see Figure 5-18)

61 | P a g e

33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 1 4 7 10 13 16 19 22 1 4 7 10 13 16 19 22 1 4 7 10 13 16 19 22 1 4 7 10 13 16 19 22 External Temp(°C) case 1 without night ventilation 3% apperture case 2 without night ventilation 5% apperture case 3 night ventilation 5% aperture case 4 with stack area 5% and apperture area 5% and night ventilation case 5 with stack area 5% and apperture area 5% and night ventilation + additional thermal mass (partitions)

Figure 5-18 Day ventilation, night ventilation and use of stacks –after TAS EDSL – Meteonorm 6.0

Figure 5-19 Model single side ventilation + stack – zoned areas in colour

62 | P a g e

6 Research outcomes and applicability The massive wood construction has the potential for the reduction of the environmental impact associated with the construction of the human habitat.

As stated before, this impact is not only associated to the consumption of energy or CO2 emissions but also with waste production during all the stages of life of the construction of the building.

As this study explores the effect of the use of this material along the life of building, I propose the following structure as a tool for the classification related to different stages of the buildings and their life. It as well, will be the structure for this chapter and as a brief in the design application of this dissertation (see Figure 6-1).

Figure 6-1 Building life stages

6.1 Production and construction As seen on chapter (3.2.1) the impact done in the production stage of materials and on site was the bigger in terms of energy use and pollution done by the construction industry in the UK as well as the demolition and production wastes were the main concern from the waste perspective Is in the possibility for waste reduction and in the possibility to produce energy out of such waste that the use of wood can help to improve the actual inefficient use of resources.

As an example of this potential the mass/energy balance is calculated for a slab and wall component based on information of embodied energy, caloric values (Berge, 2009) and waste production from wood processes (Wegener & Zimmer, 2004), as the graphic shows the waste can be reduced to minimum values and no additional energy is required to process the wood(Figure 6-2).

The wood after the buildings life can be reused or transformed in energy; if this is done there is no waste associated with demolition (Figure 6-3).

63 | P a g e

Figure 6-2 Mass balance for massive wood elements- after (Berge, 2009) (Wegener & Zimmer, 2004) the grey areas represent mass and the yellow ones energy; the bl ue framed areas represent waste (for data see Table 10-3).

64 | P a g e

Figure 6-3 Caloric value and mass of elements in Figure 6-2 (Berge, 2009) (Wegener & Zimmer, 2004) the grey areas represent mass and the yellow ones energy, the blue framed areas represent waste- If recycled wood produces no waste of demolition (for data see Table 10-3)

65 | P a g e

6.2 Energy use This project looks after the reduction of heating loads in winter and the provision of comfortable temperatures on summer, as discomfort could trigger the use of air conditioning (see precedents Calewen 4.2.1.2).

Basically, the environmental strategy used is seeking for the reduction of losses through infiltration and building fabric as the high possibility of obstructed sites makes the solar gains unreliable.

Due to the high variability of the urban gaps object of this study especially in terms of solar access two scenarios are tested one completely unobstructed facing south and one in a north orientation both with a exposed area of 100% the floor area.

As the occupant behaviour plays a major role in the energy consumption both scenarios include a test for higher thermostat setup temperatures and lower occupancy.

Factors involved in the environmental strategy were tested independently in the analytic work section. Accumulative results of the environmental strategy for heating loads reduction in winter are plotted here. .

Table 6-1 Best case scenario – Openings facing south-Different configurations-after TAS EDSL, Meteonorm 6.0

CASE 4

CASE 5

CASE 6

CASE 7

Window insulation (night shutters 40mm)

Wall insulation

Reducing comfort band (thermostat 20)

Reducing comfort band (thermos tat 21)

Reducti on of internal gains

0.35

0.35

0.2

0.2

0.2

0.2

2.0

0.9

0.6

0.6

0.6

0.6

0.6

0.35

0.15

0.15

0.15

0.15

0.15

0.15

0.15

18

18

18

18

18

20

21

20

Internal gains (KWh per year)

5000

5000

5000

5000

5000

5000

5000

2800

Internal gains (KWh/ m2per year)

66.67

66.67

66.67

66.67

66.67

66.67

66.67

37.33

heating loads (KWh/m2 per year )

13.1

8.0

4.4

3.7

2.0

4.3

5.8

10.3

Description Walls (U-value) Windows (U-Value) Infiltration (ach) Thermostat set up temperature (C)

CASE 0

CASE 1

CASE 2

CASE 3

Base case

Improve d airtightn ess

Window insulation (night shutters 20mm)

0.35

0.35

2.0

66 | P a g e

Table 6-2 Worst case scenario –Openings facing North Different configurations -after TAS EDSL, Meteonorm 6.0

CASE 0

Description Walls (U-value) Windows (UValue) Infiltration (ach) Thermostat set up temperature (C) Internal gains (KWh per year) Internal gains (KWh/ m2per year) heating loads (KWh/m2 per year )

CASE 1

Base case 0.35

Improved airtightness 0.35

CASE 2 Window insulation (night shutters 20mm) 0.35

CASE 3 Window insulation (night shutters 40mm) 0.35

CASE 4

Wall insulation 0.2

CASE 5 Reducing comfort band (thermostat 20) 0.2

CASE 6 Reducing comfort band (thermostat 21) 0.2

2.0 0.35

2.0 0.15

0.9 0.15

0.6 0.15

0.6 0.15

0.6 0.15

0.6 0.15

0.6 0.15

18

18

18

18

18

20

21

20

5000

5000

5000

5000

5000

5000

5000

2800

66.67

66.67

66.67

66.67

66.67

66.67

66.67

37.33

22.6

15.1

9.9

8.7

5.7

10.4

Reducti on of internal gains 0.2

13.2 24.5

Results show that in unobstructed conditions some improvements are at first sight unnecessary. For instance in the best case scenario (See Table 6-1) the base case start at an energy consumption of 13 KWh/m2 and just after airtight measures heating loads of 8KWh/m2 are obtained.

When the same conditions were tested in a north orientation (little solar gains) the Resulting heating loads were higher (see Table 6-2), but also within the range below 10KWh/m2 just after the improvement of the window insulation.

It is important to mention that those initial results are calculated taking into account a thermostat setup of 18Co. Even if this temperature setup could be adequate for an occupant using the adaptive opportunities to extend its range of comfort, factors as illness, age, behaviour or changes in the occupancy patterns can modify this assumption and thus the heating load results.

Another important consideration is the availability of low cost insulation from the wood shavings. As well, the possibility of its use only limited by the space lost due to the wall thickness. This improvement could contribute making the performance more robust to lack of internal and external gains, without a significant increment of embodied energy by the use of excessive insulation or additional cost.

This result proves the feasibility of the use air tight well insulated structures for different orientation and levels of obstruction when the some attention is given to keep the building expose area close to 100% of the floor area.

67 | P a g e

CASE 7

In summer: The environmental strategy to provide comfort relies on ventilation for most of the time as the external temperatures are lower than the comfort band.

During the peak hot days, with external temperatures above the comfort band, the thermal mass should be used sinking heat during the heat period and releasing it when the external temperature drops.

In the thermal simulations the proposed strategy (product of the combined effect of shading, vertically distributed ventilation and thermal mass provided by the exposed massive wood) prove to be effective for a residential use.

The vertical and horizontal distribution of the apertures proved to be effective enhancing the ventilation. Also, the recommendation of keeping the depth of the space below two times the maximum height of the window.

In the respect of the use of the thermal mass provided by the massive wood two major considerations must be taken: In the first place, the fact that heat storage capacity of the wood is lower than the one of materials as brick or concrete, therefore more area of exposed mass should be used. This is compatible with the extended use of the internal partitions as structural elements and thus massive ones.

In the second place the exposure of the thermal mass. As the thermal simulations showed, the common practice of plastering the massive wood panels diminishes the effect of the thermal mass.

6.3 Extended use of the building The life span of the buildings can be extended if measures are taken in the design stage. This in order to extend the possibilities of the building of to be re-used in the future under different conditions (occupant, market, function, climate etc) As the massive wood construction uses walls as structural loading members, risk exists in the inflexible internal layouts (see case study Stadhaus). Nevertheless this is not an inevitable situation; the use of load bearing walls is not restrictive of flexible internal layouts. This same structural principle gives to the faรงade a structural condition and thus a long durability implying the need of providing a level of indeterminacy to the windows in distribution and size.

For example, the provision of non function-specific windows will increase the opportunities of the spaces to be used for different functions and the possibilities of change in the internal layout. Other measures for adaptability are: the provision of free spaces as a possibility to grow, and the concentration of services in ducts avoiding interference between structure and pipes.

When the change of use and higher levels of occupation are contemplated, the main problem contemplated is the overheating in summer. Providing effective means for shading and ventilation proved to be adequate for achieving comfortable internal temperatures.

In the analytic work section (5.4.3.2) the test showed that well distributed windows, both vertically and horizontally, together with the 5% of the floor area as provision

68 | P a g e

for ventilation openings provided the necessary cooling in most days. Additional measures as the use of stacks to enhance the ventilation were modelled and proved lower temperatures and better performance in the hot peak days (see chapter 5.4.3.3).

To provide those stacks it is needed a prevision of 5% of the floor area in conjunction with an equivalent area of opening in faรงade. These tacks require area that; whether it is practical issue or not, its use depends of each specific project.

6.4 Demolition and material recycling The massive wood construction technique uses mechanical connections between elements meaning that elements can be disassembled without destroying them.

The use of non glued wood (Brettstapel) can also improve its recycling value without compromising air tightness (as has been tested on the Acharacle School case).

Even when the massive wood elements do not need to follow a modular approach in terms of sizes (the panels can be very big and be cut in any size), when used along with other wooden materials some modularity is advisable as board materials are done in modules related to the timber frame. Most common distances between studs (40cm or 60cm) the use of this standard sizes also improves the chances of reuse.

In a last instance, the wood can be re-used as a raw material or burned as an energy source. But designing for reuse is advisable as the longer lasting of the elements will ensure longer periods of carbon sequestration.

69 | P a g e

7 Design application.

The design application component of this dissertation explores the massive wood prefabrication as a feasible and adequate approach to its use in infill projects in urban contexts.

It aims to explore the relation between the selected material and the environmental consequences of its use as an input to the design process.

As the approach to the project was made through the design of its parts and its prefabrication processes and standards, the architectural project is now going to be explained with the same logic: from the general conception to the parts.

7.1 Design Framework / brief The proposed used for the project in the beginning was residential; even though in the frame of this study, and as a condition for the flexibility of the resulting scheme, the process was approached without use determinations as a way to expand the possibilities of the building to face changes along the time. (Nevertheless this was done while accomplishing the requirements for the proposed residential use.)

The following chart summarizes the findings of the study as they could be applied to a design project

Non glued massive wood Insulation from wood shavings Prefabrication and gap control for airtightness Mechanical connections between elements.

WINTER : Compact shape: (exposed area 100% of floor area or less ) Airtightness: air permeability of 3m3h/m2@50Pa + (PSV) + trickle ventilators.

Fabric insulation: Movable window insulation and wall u-values 0.2Wkm2 Window to floor ratio 20% -25% SUMMER: Shading : Retractable.

Ventilation: 5% of floor area vertically and horizontally distributed.

Thermal mass: Exposed to space

70 | P a g e

Flexibility : variable layout Elasticity: Area growing opportunity Indeterminacy: multi-purpose spaces.

Ventilation for higher occupancy on summer: Apertures sized for higher occupancy – aperture 5% of floor area.

Possibility of ventilation by stack.

Raw materials Mechanical connections between elements.

Layering: according to change rates.

and Ventilation.

7.1 Site The selected design application is located in Covent Garden in central London. It is a dense area with constructions of 4 to 6 storeys and narrow streets. The site’s dimension is 5 meters depth and gives little possibilities of volumetric exploration as the rational use of the available space takes priority.

The adjacent way, Mercer Street, is a narrow (7 meters wide) street with offices, retail and housing. The site is located two blocks away from Covent Garden tube station. Besides this and because of its touristic and commercial character, good transportation network characterises the area. (Buses, tube, bikes).

Figure 7-1 Site -view from mercer street

71 | P a g e

Figure 7-2 Localization

Figure 7-3 Aerial picture of site – Bing maps

72 | P a g e

Figure 7-4 Site solar access- winter - Ecotect

Figure 7-5 Site solar access – summer-Ecotect

73 | P a g e

Figure 7-6 Variation of shading requirements for different surfaces of the building -After Ecotect

74 | P a g e

The site has a T shape and the longest wing is oriented towards the southwest and the short one towards the south east. The solar access graphics above show that the lower portions of the site are obstructed during winter most of the day, while during summer days the higher solar angles allow portions of the site to be exposed to solar radiation.

7.2 Building The volume of the building follows the shape of the site and uses the blind walls of the adjacent buildings as support to occupy the site without blocking the neighbour’s access to light and sun.

The services are placed on the back against the same blind walls, acting as a continuous duct for services. This is complimented with the raised floor of the building’s floors, allowing different internal layouts and flexibility on the services location as the provision of continuous space for services. The stairs are proposed in the intersection of the wings of the T and extra space for circulation is provided to allow to the portions of the building to be join without compromising the vertical circulation (See Figure 7-7) The structure is formed by massive wood panels, the facade has a structural function, special care has been taken in the arrangement of elements in order to allow connexion between adjacent spaces (See Figure 7-8) The exposed area of the building’s envelope is kept about 100% of the floor area, with the exception of the flat E in top floor with higher exposure (See Figure 10-2).

Nevertheless, as is located in the unobstructed portion of the scheme, (obstruction o angle 15 ) it can take advantage of the solar gains.

Figure 7-7 Schematic plan.-Grey areas are habitable spaces, blue areas are vertical voids, green areas are service ducts the central blank area is used for vertical circulation.

75 | P a g e

Figure 7-8 Proposed structure- Interconnectivity between spaces Table 7-1 Flat areas and exposure ratio

Floor 1

floor area

flat A flat B flat C flat D flat E flat F

72.00 60.04 47.25 47.25

Floor 2

exposed area

66.15 32.21 26.90 30.67

floor area

76.44 36.73 38.41 47.25

Floor 3

exposed area

floor area

exposed area

floor area

66.15 32.29 65.31 77.92 65.25 60.04

76 | P a g e

Floor 4

50.45 32.26

84.57 60.04

exposed area

FLAT exposed area /floor area

FLAT Area

0.89 148.44 0.67 96.77 1.08 85.66 1.15 94.50 160.27 1.41 149.82 92.39 1.04 120.08 695.27 Total area

Figure 7-9 Proposed Plans

77 | P a g e

7.3 Parts 7.3.1 Basic construction order The ‘basic construction’ order is the result of the analysis of the actual use of massive wood construction in the various cases studied and the recommendations extracted from the theoretical and analytic work.

In this sense the ‘basic constructive’ logic aims to: a) Keep a simple primary air barrier that can be done/checked /repaired/inspected at the end of the construction sequence or during the use of the building. b) Provide a continuous insulation layer avoiding thermal bridging and to expose internally the thermal mass provided by the wood. c) Compliance with additional requirements like sound insulation, and provision for services without covering the thermal mass.

Figure 7-10 Typical facade section

78 | P a g e

7.3.2 Element sizing (fabrication – and offsite): The prefabrication and offsite production are part of the environmental strategy of the project, as it is linked to the joint quality necessary for the achievement of air tightness and low waste volumes.

The elements in massive wood can be cut to fit size for different cases with no impact on the production time, but as mentioned before, some modularity is amendable for material optimum use. For this reason, the design is of the building is based on smaller parts designed or ruled by the criteria exposed in the design brief.

The sizing of elements in the facade obeys to different criteria: a)

the modules are sized accordingly to the modular sizes used in commercial boarding products (multiples of 40cm-60cm) b) The windows are sized to keep a window to floor ratio between 20% and 25% as the maximum distance from a window is maintained below 5m. c) The area and location of windows is arranged in a way that the spaces can be subdivided down to small sizes (for instance 1.6m for a small bathroom) and still being able to have a window of their own while bigger spaces will have more windows.

Following the above mentioned criteria, slabs and walls should be prefabricated in 5 sizes limited by the logistics of urban transportation The window size and shape is done to enhance the daylight provision by the use of high windows that obstruct the lesser amount of sky component (See Figure 7-11).

Figure 7-11 Modules for prefabrication 5

A typical truck can carry sizes up to 3m height * 2m width *6m length.

79 | P a g e

Figure 7-12 Constructive breakdown

7.3.3 Module design and occupant use: The elements are also designed to provide to the users control in his relation with the external environment. They are also essential part of the energy efficiency measures of the project’s design.

It is important to mention that the element design is related to the environmental strategies for winter and summer.

80 | P a g e

7. 3 .3 . 1 Wi nt e r:

General strategy: The winter strategy relies on airtightness, controlled ventilation, compact shape and fabric insulation, including movable insulation for the windows.

Mechanical ventilation is avoided as noise was reported as a problem by the inhabitants of the case studies.

Figure 7-13 Winter Airtightness primary and secondary air barrier - ventilation

Ventilation: As the strategy for winter relies on airtightness, the provision of fresh air for the inhabitants should be provided by background ventilation. This should be done by the use of trickle ventilators (see Figure 7-13).

The requirement for its provision is between 6000 mm2 and 8000mm2 depending on the space covered.

81 | P a g e

The dissipation of specially polluted spaces (as bathrooms or kitchens) could be problematic and the trickle ventilators would not sufficient. For this reason, the use of passive stack ventilation ducts is proposed.

Fabric insulation: The window to floor ratio proposed 20-25% was chosen as a provision for daylight even when lower amounts of fenestration showed better energy performances.

Because the solar access is restricted in the winter, the fenestration area is not differenced between north and south orientations, as conditions for solar access in winter are similar for different orientations excepting the unobstructed upper floors.

The movable insulation or night shutters provided can help to overcome this contradiction between the better performance of lower areas of fenestration and the need of daylight, allowing increasing the level of insulation for spaces when not used during the night, or when the requirement for daylight allows smaller apertures. These proposed elements allow different aperture configurations conciliating the regular indeterminacy of the spaces with the provision of the possibility of fine- tuning to the occupants.

Figure 7-14

Daylight: The basic recommendations in relation between the height of the windows and the depth of the space (Baker & Steemers, DAYLIGHT DESIGN OF 82 | P a g e

BUILDINGS , 2002) are followed. The space never exceeds 2 times the distance to the window.

The layout of the proposed windows is proposed to be vertically arranged. This because of two reasons: the need of vertical continuous elements (as the facade has a structural function) and the distribution of the window area in a way that much of the area remains higher than the working plane.

The values required for dwellings were tested for both: unobstructed conditions and o for an obstruction angle of 45 . In both cases the requirements for dwellings were exceeded.

The benchmark used is: Dwellings requirement- general rooms: average DF 1.5% and minimum DF 0.5% Dwellings Requirement- Kitchen: Average DF 2.0 and minimum DF 0.6% (Baker & Steemers, 2002) The building was expected to provide values above the minimum values required for dwellings to make possible low artificial use of lighting in another uses.

Nevertheless this is difficult to achieve due to the obstruction of the surroundings in the lower floors which reduce the portion of visible sky. In order to overcome this, double height areas are proposed as a way to provide zones of better daylight in the lower floors allowing mixed use dwellings (See Figure 7-9,Figure 7-17) The benchmark used is: Offices requirement: Average DF 3% and minimum DF 1.0% (Baker & Steemers, 2002)

Figure 7-15 Daylight factor in overcast CIE sky-single storey space – windows transmittance 0.69 walls reflectance0.6 – unobstructed site- Average DF 2.78% -After Radiance

83 | P a g e

Figure 7-16 Daylight factor in overcast CIE sky -single storey space – windows transmittance 0.69 walls reflectance0.6 –site with obstruction angle 45o Average DF 1.78% -After Radiance

Figure 7-17 Daylight factor in overcast CIE sky – double height – windows transmittance 0.69 walls reflectance0.6 –site with obstruction angle 45 o Average DF 2.9%-After Radiance

84 | P a g e

7. 3 .3 . 2 Su mm e r: General strategy: The summer strategy relies on shading and ventilation for the average summer days (See Figure 7-18). In peak hot days additional to shading, thermal mass as heat sinks during the day and night ventilation (see Figure 7-19).

Figure 7-18 Average summer day strategy

85 | P a g e

Figure 7-19 Summer hot day strategy

Shading: As the orientation is one of the factors that vary between projects, and even between different portions of the same project, the purpose is to design shading elements that respond and at the same time are effective and adequate for the project’s location and orientation.

The proposed shading devise to be used is retractable, and thus designed to cap the solar radiation related to the solar geometry of the summer period.

To optimise this task, the software used is Grasshopper plug-in used along with 6 rhinoceros. The methodology used for the design of the “script" is based on the one proposed by Szokolay (Szokolay S. V., Introduction to architectural science: The Basis of Sustainable Design, 2008) and requires the previous identification of the critical shadow angles (horizontal and vertical) in a sun path diagram according to 7 the buildings orientation and shading requirements .

6

This software allows to generate geometry from a group of commands and parameters and to modify such parameters affecting the resulting geometry output.

7

“Shadow angles express the sun's position in relation to a building face of Given orientation (...)

Horizontal shadow angle (HSA) is the difference in azimuth between the sun's position and the orientation of the building face considered.

HSA = AZI – ORI The vertical shadow angle (VSA) is measured on a plane perpendicular to the building face(...)the VSA is the same as the solar altitude angle VSA =ALT”

86 | P a g e

The VSA and the HSA are then used as input parameters to build the geometry for the shading devices in relation to the size of the surface to shade (see Figure 7-20 and Figure 7-21) The same performance can be achieved with the use of several smaller elements obstructing the same angles (see Figure 7-20 and Figure 7-21) and allowing the design of thinner shading devices.

Is important to say that in some orientations (for example in west facades in the afternoons) the sun is located perpendicular to the face to shade; a fin perpendicular to the face will tend to be infinite when obstructing the specified angle. For this reason the vertical fins proposed are tilted allowing the protection from sun positions perpendicular to the facade to shade (see Figure 7-22).

Figure 7-20 SECTION Shading design – Overhang (single and multiple elements)

Figure 7-21 PLAN Shading design – Overhang (single and multiple elements)

Another aim of the “script” was to allow variations on the position of the fins to create a less monotonous effect on the interior. As well, zones or spots with bigger gaps between fins without increasing the thickness of the whole shading device but the desired zone. This is done by the use of attractors or points (see Figure 7-23).

The distance between each fin of the array and the attractor affects the size of the gap (see “x” in Figure 7-22) between fins.

(Szokolay S. V., Solar geometry, 2007)

87 | P a g e

Figure 7-22 PLAN vertical fins “tilted” in different angles and resulting different values for “x”

Figure 7-23 Diagram for variations the vertical fins, as the distance between the fins and the light areas “attractors” is lower the value for X (see Figure 7-23) increases creating “Peep holes” on the shade.

As the geometry is generated along a vector correspondent with the HSA, the variations of the geometry did not affect the performance of the shade. This allows the proposed conceptual design to be adapted to different shading requirements as shade thickness, number of cells, HSA, VSA; and to be produced by computer numerical control machines (CNC). Nevertheless in order to minimize waste and simplify the assemblage, the design concept seeks to develop a way to produce complex shapes by the use of simple elements.

It is important to mention that in some orientations or obstruction conditions, one of the solar angles does not need to be shaded. For example: when a building is obstructing the late afternoon light in a west orientation, the only component to be obstructed is the vertical VSA. In these situations the unused elements could be sized to its minimum size, just to have a function as structure for the shading device. The strategy can also be inverted in certain cases so the tilted elements are the overhangs obstructing the VSA.

88 | P a g e

Figure 7-24 Internal view of shaded windows

89 | P a g e

90 | P a g e

Ventilation: The basic principle for the design of the ventilation is the vertical and horizontal distribution of the apertures, in order to take advantage of the differences of pressure along the facade.

The aperture areas are sized to be equivalent to a 5% of the floor area for a module of depth 5m (that is the maximum single sided depth of plan in the scheme).

The upper apertures are designed to provide ventilation directly towards the exposed thermal mass in the ceiling.

Thermal mass: The massive wood panels are exposed towards the interior of the space facing walls and ceilings. In order to accomplish sound requirements and provision of services on a raised floor, the panels are covered in the floor. This position was found preferable as is probable that the occupants will anyway cover it with furniture.

91 | P a g e

Figure 7-25 Proposal from mercer stree

92 | P a g e

Figure 7-26 Proposal Communal terrace

93 | P a g e

Figure 7-27 Proposal View from Shelton St- Mercer St corner

94 | P a g e

Figure 7-28 Facade different stages

95 | P a g e

Figure 7-29 Proposed plans

96 | P a g e

Figure 7-30 proposed plans

97 | P a g e

8 Conclusions The use of massive timber provides an opportunity in the reduction of the environmental impact in the construction in the UK. As mentioned throughout this report, some of its benefits are derived from a cleaner production as well as from its easy re-use and recycling; also, from the possibility of producing energy out of its waste.

The use of wood can be extended towards any kind of building. This due to the fact that apparent limitations in height related to its structural behaviour or in relation with fire security can be solved.

The way in which massive wood structures are produced and prefabricated result as a positive input when used: the building will present low levels of air infiltration, which are an important effect in the reduction of heat losses. It also implies dramatic reductions on energy consumption (75% for the lowest infiltration rates measures) in relation to the building regulations specification. Because it is possible to insulate the walls with the use of wood shavings, the specification of optimum insulation levels is restricted by the available space and not by the cost of the material or of the control of the embodied energy of the building.

The use the above mentioned characteristics together with its application in compact buildings constructed in urban infill, (which in this case is a site in central London) makes possible low energy consumptions when related to heating even on obstructed or north oriented sites. It also makes possible to rely mostly on the internal gains from occupants and appliances. Nevertheless, this bigger reliance on internal gains due to the variable nature of occupants, requires a robust passive heating strategy; is here where the “free“ additional levels of insulation can overcome differences in the use patterns.

The massive nature of the timber helps to provide good internal conditions in the building by regulating humidity and temperature variations. This is very useful in the hot days in summer when the thermal mass can act as a heat sink during the day and dissipated through night ventilation. These combined characteristics can extend as well the adaptability of the building to a climate change scenario.

In relation with all of the above, the main intension of the design application was to frame the design process within an environmental strategy taking into consideration: from the material selection to the provisions for durability and recycling. Thus, the selection of the site acted as testing ground, implying that the applicability of the design strategy of this report can take place in the site chose or in other any urban infill site.

One of the main exploration held during the design process was the incorporation of the production logic of the material into the design, and as a tool to explore two ways of prefabricated production: first, by taking advantage of its regularity and existing modular production, and the second, (used for the shading design) allowing to site specific parameters generate changes in the design.

This results in a very modular regular shape, with a changing appearance due to the dynamic characteristic of the adaptable skin of the building.

Finally, I will like to mention that one of the interesting aspects of the process was how these intentions affected the design process itself. It helped it to evolve (at least as design intention) from a deterministic approach, based on the solution of short term problems, towards an approach based on providing possibilities for things to happen to the building in a uncertain future.

98 | P a g e

9 References Auliciems, A., & Szokolay, S. V. (2007). Thermal comfort. Queensland: PLEA: Passive and Low Energy Architecture International.

Baker, N. REVIVAL technical monogram 2:Adaptive thermal comfort and controls for building refurbishment. Revival.

Baker, N., & Steemers, K. (2002). DAYLIGHT DESIGN OF BUILDINGS . London: James and James (science publishers).

Baufritz UK ltd. (n.d.). Baufritz. Retrieved from http://www.baufritz.co.uk/why_ecology.asp#diagram Bell, M. (2006). Airtightness of buildings. Towards higher performance. Interim Report to Communities and Local Government Building.

Bell, M., Johnson, D., Miles-Shenton, D., & Wingfiled, J. (2007). Airtightness of UK dwellings: some recent measurements. RICS COBRA conference at Leeds Metropolitan University. Leeds: RICS Foundation.

Berge, B. (2009). The ecology of building materials. Oxford: Elsevier.

Boardman, B., Darby, S., Killip, G., Hinnells, M., Jardine, C., Palmer, J., et al. (2005).

40% house. Oxford: Environmental change institute university of oxford.

Bridgestock, M., Foster, S., & Henderson, J. (2010, December). Brettstapel Construction. Retrieved January 20, 2011, from http://www.brettstapel.org/Brettstapel/Home.html CIBSE. (2006). Guide A: Environmental Design . London: Chartered Institution of Building Services.

CIBSE. (2006). Guide A: Environmental Design. London: Chartered Institution of Building Services Engineers.

Davies, C. (2005). The Prefabricated Home. London: Reaktion books.

Department of trade and industry/national statistics. (2010). Energy consumption in the united kingdom (updated data tables 2010 update). Retrieved July 31, 2010, from Department of energy and cimate change.: http://www.decc.gov.uk/publications/basket.aspx?filetype=4&filepath=Statistics/p ublications/ecuk/269-ecuk-domestic-2010.xls&minwidth=true Dinwoodie, J. (2000). Timber, its nature and behaviour. Abingdong, Oxon: Taylor & Francis .

Edwards, R. (2005). Handbook of domestic ventilation. Oxford: Elsevier.

Ford, B., Schiano-Phan, R., & Zhongcheng, D. (2007). The passivhaus standard in european warm climates:Design guidelines for comfortable low energy homes.

European Commission project Passive-on.

Grantham, R., & Enjily, V. (2003). Multi-storey timber frame buildings: a design guide. London: BRE bookshop.

99 | P a g e

Griffiths, P. J., Kersey, J. R., & Smith, R. A. (2002). The construction industry mass balance:Resource use, wastes and emissions. Viridis.

Grindley, R. (2010, July 3). Architect - David Grindley architects. (F. Serrano, Interviewer) Hacker, J., Belcher, S., & Connell, R. (2005). BEATING THE HEAT: Keeping UK buildings cool in a warming climate. Oxford: UKCIP. Jaggs, M., & Scivyer, C. (2006). Achieving airtightness:general principles.

Garston,Watford: BRE press.

James, M., & Brand, S. (Directors). (1997). How buildings learn [Motion Picture].

KLH UK. (n.d.). KLH UK. Retrieved January 20, 2011, from http://www.klhuk.com Mc Guiness, T. (2010, August 10). (F. Serrano, Interviewer) PassivHaus Institut Darmstadt. (n.d.). Passivhaus primer. Retrieved September 2010, from http://www.passivhaus.org.uk/filelibrary/BRE-PassivHaus-Primer.pdf Ross, P., Downes, G., & Lawrence, A. (2009). Timber in contemporary architecture: a designer's guide. High wycombe: TRADA technology ltd.

Sohm. (n.d.). Sohm. Retrieved 12 2010, from http://www.sohmholzbau.at/uploads/DD.pdf Szokolay, S. V. (2007). Solar geometry. Brisbane: PLEA: Passive and Low Energy Architecture International.

Szokolay, S. V. (2008). Introduction to architectural science: The Basis of Sustainable Design. Oxford: Elsevier .

Szokolay, S., & Zold, A. (1997). Thermal insualtion. Queensland: PLEA: Passive and Low Energy Architecture International.

Thompson, H. (2009). A process revealed. London: Andrew waught ,Karl Heinz Weiss, Matthew Wells.

Till, J., & Schneider, T. (2007). Flexible Housing. Oxford: Elsevier.

Till, J., Wigglesworth, S., & Schenider, T. (n.d.). Flexible housing. Retrieved 12 10, 2010, from http://afewthoughts.co.uk/flexiblehousing/about.php TRADA in association with UK timber frame association. (2007). Fire performance of timber frame dwellings,Wood information sheet. High Wycombe: TRADA Technology Ltd. TRADA. (2010). Timber Solution / Massive timber construction without glue Brettstapel. High Wycombe: TRADA Technology .

Weather underground. (n.d.). Retrieved July 2010, from http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IBUCKING 30

100 | P a g e

Wegener, G., & Zimmer, B. (2004). Building with wood is building for the future. In T. Herzog, Timber construction manual. (pp. 47-49). Basel: Birkhauser.

Yannas, S. (2000). Designing for summer comfort: Heat gain control and passive cooling of buildings.

YANNAS, S. (1994). Solar energy and housing design. London: Architectural association publications.

101 | P a g e

10 Appendix

Table 10-1 Different wall construction u-value calculation

thermal resistance

thickness

thermal conducti vity

R

L

λ

m2 K/W

m

W/m K

layer

description

massive wood

Rsi

0.125

R1

1.000

0.130

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

1.111

0.050

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

ΣR

2.487

U-value total thickness

0.40

Rsi

0.125

R1

1.000

0.130

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

1.444

0.065

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

rinsed slightly compressed wood shavings (Berge, 2009) plywood

0.21

ΣR

2.820

U-value total thickness

0.35 0.23

102 | P a g e

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

Rsi

0.125

R1

0.923

0.120

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

2.000

0.090

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

ΣR

3.299

U-value total thickness

0.30

Rsi

0.125

R1

0.923

0.120

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

2.667

0.120

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

0.24

ΣR

3.966

U-value total thickness

0.25

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

0.27

Rsi

0.125

R1

0.923

0.120

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

3.778

0.170

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

ΣR

5.077

U-value total thickness

0.20 0.32

103 | P a g e

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

Rsi

0.125

R1

0.923

0.120

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

5.556

0.250

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

ΣR

6.854

U-value total thickness

0.15

Rsi

0.125

R1

0.923

0.120

0.13

Inside surface resistance SOLID TIMBER (structural wall)

R2

0.077

0.010

0.13

BOARDING

R3

8.444

0.380

0.045

INSULATION

R4

0.154

0.020

0.13

Rso

0.020

BOARDING Outside surface resistance

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

0.40

ΣR

9.743

U-value total thickness

0.10 0.53

104 | P a g e

massive wood rinsed slightly compressed wood shavings (Berge, 2009) plywood

10-2 Thermal storage for different materials - after (Yannas, 2000) (KLH UK)

volume of 1m2 (m3)

thickness (m) wall properties

0.10

0.1

massive wood (spruce cross laminated)

conductivity

density Volumetric heat capacity

rate of heat flow energy required to raise temperature 1k in 1 kg of material (also sotrage) energy required to raise temperature 1k in 1 kg of material (also sotrage) mass per unit of volume density * specific heat

heat storage per m2

volumetric heat capacity * volume

Specific heat capacity J/(kg K)

Specific heat capacity Wh Kg K

THERMAL DIFFUSIVITY TRANSLATED TO TIME for the wall thickness

ratio of thermal conductivity to volumetric heat capacity (depth change of temperature penetrate over time ) T=DEPTH SQ /DIFFUSIVITY

0.1

CONCRETE

0.1

BRICKWORK

0.44

Wh Kg K

0.23

Wh Kg K

0.22

Wh Kg K

400

kg/m3

2100

kg/m3

1700

kg/m3

0.18

KWh m3 k

0.48

KWh m3 k

0.37

KWh m3 k

2.0E-07

288.44

M2/S

seconds

W/(m K)

0.10

J/(kg K)

KWh k

1.4

volume (of 1m2)

1600

0.018

105 | P a g e

0.10

thickness (m)

W/(m K)

13.68

THERMAL EFFUSIVITY

volume (of 1m2)

0.13

49230.77

How easy heat is absorbed at the surface of material

thickness (m)

0.84

J/(kg K)

0.048

8.1E-07

12420.00

KWh k

M2/s

seconds

W/(m K)

J/(kg K)

0.037

6.2E-07

16028.57

KWh k

M2/s

seconds

hours

3.45

hours

4.45

hours

Ws0.5M2k

0.82

Ws0.5M2k

0.56

Ws0.5M2k

T=DEPTH (2) /DIFFUSIVITY 35.00 30.00

TIME (HOURS)

25.00 20.00 15.00 10.00 5.00 0.00

0.025

0.05

0.075

0.1

0.125

0.15

CLP

0.85

3.42

7.69

13.68

21.37

30.77

CONCRETE

0.22

0.86

1.94

3.45

5.39

7.76

BRICK

0.28

1.11

2.5

4.45

6.96

10.02

THICKNESS (M) Figure 10-1 Thickness versus time required to temperature in the interior of the element after (Yannas, 2000)

106 | P a g e

Figure 10-2 Floor area - exposed area 107 | P a g e

Table 10-3 Embodied energy and mass for components in Figures 6.2 and 6.3

h

w

d

density kg/m3

m3

weight kg

waste produced (from trunk1.4kg for each kg )

wall

2.85

0.8

0.13

0.2964

480

142.272

199.2

slab

5

0.8

0.13

0.52

480

249.6

349.4

boading

3

0.8

0.02

0.048

500

24

0.0

415.872

*boarding usually produced out of waste

use of waste : h insulation

w 3

d 0.8

density kg/m3

m3 0.15

0.36

weight kg 80

28.8

total mass used KG

415.9

total waste Kg

548.6

source (Wegener & Zimmer, 2004)

calorific value of waste MJ per kg

17.0

source (Berge 2009)

Total calorific value of waste produced Mj

9326.6

total used + waste

964.5

resulting waste for biomass or boarding products (after insulation use) calorific value of waste per kg ( MJ per Kg) embodied energy of laminated product (kiln dryed and saw MJ per Kg)

519.8

kg

17.0

MJ/Kg

21.0

MJ/Kg

total embodied energy structure MJ

8733.3

MJ

total calorific value of waste Mj

8837.0

MJ

surplus energy

103.6

MJ

used mass on energy

513.7

Kg

6.1

Kg

7069.824

MJ

Surplus mass caloric value of building at demolition stage

108 | P a g e

source (Wegener & Zimmer, 2004) source (Berge 2009) source (Berge 2009)