INSULATION | AIRTIGHTNESS | BUILDING SCIENCE | VENTILATION | GREEN MATERIALS
S U S TA I N A B L E B U I L D I N G
PITCH PERFECT Beguiling Dundee passive
Six build specs compared
3D printed buildings The future or a wasteful distraction?
Cambridge chooses passive house for King’s College students
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house puts wood into woodland
SAME HOUSE, DIFFERENT HOME.
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editor’s letter I
have to stop going down rabbit holes. Over recent weeks I’ve been digging deeper into two particularly labyrinthine tunnels – on building life cycle assessment and thermal comfort standards. Readers will have to wait till our autumn issue before we have something to report in the latter case, but suffice to say it raises some extremely important questions about how to reconcile the need for profound energy reductions against achieving healthy, comfortable conditions in buildings during winter and summer. Questions which the passive house standard may be best placed to answer. I have emerged into the daylight from the life cycle assessment rabbit hole – for now at least – and now comes the business of trying to work out what I’ve learned. The main findings from this experience are manifest in this latest issue of Passive House Plus, in the whole life carbon calculations and building models on six build specs that Tim Martel and Andy Simmonds of the AECB undertook for the Passive House Association of Ireland, working with PHAI board member John Morehead and myself. They’re also manifest in our collaboration with sustainable building consultant John Butler to calculate the embodied carbon of two of the case studies in this issue, and in our interpretation of the revised embodied carbon targets in the RIBA 2030 Climate Challenge. At first glance it looks like a terrible climbdown – RIBA’s 2030 embodied carbon targets for dwellings have risen from 300 to 625 kg CO2e/m2, after all. And the PHAI / AECB analysis came up with some stark findings: all of the six variants of build spec analysed, including a typical cavity wall spec, seem likely to meet the 2030 target – notwithstanding the fact that the analysis did not include certain elements of the spec, such as the building services, other than a heat pump. It will be important to consider the assumptions contained within the calculations,
ISSUE 38 for instance with regard to maintenance, replacements and repair, within the sixty-year life span assumed in the RIBA targets. And there is also a legitimate question to ask about whether targets should only be set on a cradle to grave basis. Of course, it’s critically important to think of emissions over the lifespan of a building, and at its end of life. But it’s incumbent upon us to focus on the here and now too, given how little wiggle room we have on emissions if we are to have any chance of preventing the worst outcomes in the climate emergency. So, we must focus on radically reducing the emissions we put into the atmosphere now. That starts by focusing on repurposing buildings instead of building new, where possible. Where we have to build we must try to build smaller, build in the right places, and then ensure that when we build and renovate, we balance minimisation of upfront emissions against minimisation of emissions throughout the building’s life – both for energy use and for maintaining the building – and that we place an emphasis on build quality, repairability and ultimately, de-constructability, to ensure the longest lifespan possible, and to enable future uses of a building’s constituent parts. It’s not easy sticking your neck out and setting targets. RIBA deserves great credit for taking the initiative by including embodied carbon targets in the 2030 Climate Challenge. And there’s a palpable sense of RIBA’s openness, transparency, and keenness to collaborate in advancing our shared understanding what we need to do on embodied carbon. But if the revised 2030 targets risk making business as usual look like sustainable virtue, RIBA has an obligation to act, and to set targets that will force the industry to up its game. Regards, The editor
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Dundee passive house Photo by David Barbour
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CONTENTS COVER STORY
INTERNATIONAL This issue features a new nursery school in Paris, built to the Passive House Institute’s low energy building standard.
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NEWS RIBA loosens its 2030 embodied carbon targets, the UK Passivhaus Awards winners are announced, and CO2 monitors become the new tool in the fight against Covid-19.
COMMENT In his latest column, Dr Marc Ó Riain takes a look back at the some of the first projects to address the phenomena of thermal bridging and thermal bypass in buildings; and Dr Peter Rickaby writes about why the Green Homes Grant scheme failed.
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CASE STUDIES King’s comfort Cambridge choses passive house comfort for Kings’ College students
Most people think of cold, cramped and poor-quality buildings when they think of student accommodation, but two new passive house residences at King’s College, Cambridge are rewriting the rulebook, with their focus on occupant comfort, architectural quality, and an enlightened, long-term view of construction costs.
Pitch perfect Beguiling Dundee passive house puts wood into woodland
An intriguing new passive house in Dundee takes the traditional ‘box’ form associated with the standard and turns it on its head, using a series of pitched roofs and different claddings to make it feel more like a traditional city terrace than a single dwelling – built with a heavy emphasis on carbon sequestering materials.
The climate emergency demands that we minimise the energy we use to operate buildings, as well as the energy we use to construct new buildings, where new buildings are needed. A Passive House Association of Ireland-commissioned analysis may start to shed some light on the embodied carbon impact that different build methods can have.
MARKETPLACE Keep up with the latest developments from some of the leading companies in sustainable building, including new product innovations, project updates and more.
Butterfly effect Sligo deep retrofit delivers warmth, light and sweeping mountain views
Complete with butterfly roofed extension, this fabricfirst renovation has turned a cold and uninspiring 1970s bungalow into a cosy A-rated modern home, with some clever design touches helping to open the house up to wide-angle views and dramatic coastal light.
INSIGHT Six of one An analysis of the embodied carbon from six ways of building a house
Above the curve Limerick passive house showcases precision timber engineering
Sometimes it takes the constraints of a challenging site to bring out the best possible design, and that was certainly the case for this Limerick City passive house, where the project team managed to deliver a unique, curving passive house in response to a tricky urban plot.
On the 3D printing of buildings
Building physics expert Toby Cambray finds himself unconvinced by the merits of a new home in the Netherlands that has been 3D printed with concrete.
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INTERNATIONAL PAS S I VE & EC O B U I LDS F R O M AROU ND THE WORLD IN BRIEF Building: 1,500 m2 nursery school Location: 13th arrondissement, Paris Building method: Timber frame with straw insulation Standard: PHI Low Energy Building Standard
I N T E R N AT I O N A L
Photos by Charly Broyez Planchers et toitures en CLT
Planchers et toitures en CLT
Murs à ossature bois & Isolation Paille et Laine de bois
Murs à ossature bois & Isolation Paille et Laine de bois
Planchers et toitures en CLT
Planchers et toitures en CLT
Murs à ossature bois & Isolation Paille et Laine de bois
Murs à ossature bois & Isolation Paille et Laine de bois
Voiles en Béton armé
LEFT Voiles en Béton armé
PRINCIPESSCHOOL, CONSTRUCTIFS BANK NURSERY OssaturePARIS Bois
Voiles en Béton armé
Axonométries de principe
he challenge for the designers of this new nursery school, set within Paris’s Left Bank, was to create a space that would be warm, light-filled and conducive to learning — but in a dense city centre environment that is overlooked by tall, monolithic apartment blocks of the 13th arrondissement. The building’s PRINCIPESdesigners, CONSTRUCTIFSLA Architectures, achieved their goal Axonométries de principe beautifully by breaking down the building into multiple volumes. PRINCIPES CONSTRUCTIFS Voiles en Béton armé Ossature Bois While not ideal for meeting the passive house standard — it means Axonométries de principe a larger surface area from which heat can escape, and more junctions that need to be sealed for airtightness — it does help to create a more human-centred building in the middle of an otherwise imposing streetscape. Another technique employed by the architects to bring light into the school was Le Corbusier’s beloved “architectural promenades”. These inner streets meander through the building, and with their PRINCIPES CONSTRUCTIFS glazed walls, open up the space and allow occupants to look out Axonométries de principe
through the classrooms to the courtyard beyond. Indeed, the school has been designed so that there is a view to the outside at almost every point. LA Architectures also placed a strong emphasis on natural materials here: the walls are of timber frame construction and insulated with straw, with floors and interior walls of cross-laminated timber. There is also a green roof, timber cladding, and a brickwork that was made in one of Paris’s last traditional old kilns. The building did not quite meet the passive house standard — at 28 kWh/m2/yr, its demand for space heating is outside the passive benchmark of 15 kWh/m2/yr — so instead it was certified to its less onerous cousin, the Passive House Institute’s low energy building standard (which only requires 30 kWh/m2/yr). But all in all, the thoughtful approach to materials, natural light and occupant comfort here must make this one of the most joyful places for children to learn in Paris’s busy urban centre.
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Cavity wall builds can meet RIBA carbon targets, new analysis suggests Words by Lenny Antonelli and Jeff Colley
detailed analysis of the embodied carbon of six common build types has indicated that dwellings built with businessas-usual build specs of cavity wall construction and strip foundations may be able to meet the revised embodied carbon targets for dwellings in RIBA’s 2030 Climate Challenge. The RIBA document has come under scrutiny recently after its 2030 embodied carbon target for dwellings was eased from 300 to 625 kilograms of CO2 equivalent per square metre (kgCO2e/m2). The analysis, published elsewhere in this issue of Passive House Plus, was commissioned by the Passive House Association of Ireland (PHAI) and undertaken by the Association for Environment Conscious Building (AECB). A house design for a social housing unit with 84 m2 gross internal area (GIA) provided by Cork City Council was analysed using six different variations of wall and foundation specs. The analysis also included specs for roof, intermediate floors, stud walls, windows, and an air-to-water heat pump, but excluded items such as fixed furniture and equipment, ventilation, heating and water distribution systems, tiling and staircase. The base case included two variations – a brick clad cavity wall, and a rendered block cavity wall, both on conventional strip foundations. The brick clad option totalled 526 kgCO2e/m2 GIA, indicating it would likely comply if the missing elements were included. The rendered cavity wall build and a single leaf 215 mm block with external insulation, both on conventional foundations, respectively totalled 496 and 492 kgCO2e/m2. Meanwhile a variant including cellulose-insulated timber frame with cement boards and insulated foundations integrating 50 per cent GGBS totalled 369 kgCO2e/m2. RIBA has defended its decision to make the embodied targets in its 2030 Climate Challenge significantly easier to achieve. The previous target of 500 kgCO2e/m2 for non-domestic buildings has also been replaced by two separate targets: 540 kgCO2e/m2 for schools and 750 kgCO2e/m2 for offices. The 2025 target for operational energy in dwellings has been tightened from 70 to 60 kWh/m2/ yr. However, it is the change to the embodied carbon target for domestic buildings that has raised most eyebrows.
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“Seeking radical, systemic change is one of the core values that brings us together as a network, ” Joe Giddings of the Architects’ Climate Action Network told the Architects’ Journal. “So many, including myself, were disappointed to see RIBA climbdown on their targets for 2030.” However, RIBA defended the changes, and said the new targets aligned it with similar benchmarks set by other organisations. “When we launched the 2030 Climate Challenge two years ago, we set initial targets, but were clear that these would evolve,” said RIBA president Alan Jones. “Since then, industry knowledge and data has significantly increased, and we have worked closely with key organisations such as LETI, IstructE, UKGBC and the Whole Life Carbon Network to ensure that our embodied carbon targets and approaches are aligned and consistent. “The embodied carbon targets have been refined based on more accurate benchmarks, but the 2030 targets for operational energy and potable water use remain unchanged, and some sector-specific 2025 targets for energy consumption have been tightened. “To successfully reduce the huge negative impact of construction, we must collaborate across the entire sector and, as architects specifically, change our approach to designing buildings. These targets are ambitious, but achievable. I urge all practices to sign-up to the challenge. We need to attempt to achieve these targets on our projects now.” The LETI (London Energy Transformation Initiative) has set it owns benchmarks for embodied carbon, and RIBA’s new targets coincide with a ‘B’ rating under LETI’s system, but LETI also assigns more ambitious A, A+ and A++ ratings for buildings that achieve under 450, 300 and 150 kgCO2e/m2 respectively. However, while LETI’s targets exclude the up-front carbon footprint of on-site renewable electricity generators, RIBA includes them, leading to questions about how comparable the two benchmarks are. Speaking to Passive House Plus, the passive house architect Mark Siddall, a technical advisor to both the AECB and the Passivhaus Trust, said he thinks the previous target of 300 kgCO2e/m2 was very onerous, given that it includes building life cycle stages A (product
stage and construction process) through to C (end of life). However, he questioned whether the embodied carbon of on-site renewable energy systems should be included in the target, as he said this would mean a theoretical dwelling with no “bolt on” renewable energy systems, and that only pays rudimentary attention to the embodied carbon of its building fabric, could produce a similar embodied carbon score to a dwelling with low embodied carbon fabric and a solar PV system. He gave the example of his Larch Corner passive house in Warwickshire, for which the solar PV system accounted for about one-quarter of the stage A embodied carbon score. He suggested that the embodied carbon of on-site “bolt on” renewables such as solar PV should be reported, but not included in the main target. The RIBA 2030 requirements require calculation of embodied carbon in accordance with the RICS guidance document, ‘Whole life carbon assessment for the built environment’, with analyses to include including a minimum of 95 per cent of the cost, and seven of eight building element groups, including substructure, superstructure, finishes, fixed FF&E, building services and associated refrigerant leakage. The exception is external works. Speaking to Passive House Plus, RIBA sustainable development advisor Jess Hrivnak said: “We appreciate many projects won’t be undertaking whole life carbon assessments as part of normal project programme. The intention is not that projects should do these retrospectively for the sole purpose of data collection.” Hrivnak said RIBA is interested in understanding if no whole life carbon assessment took place, why not. Or – if high level embodied carbon evaluation was undertaken – the scope and stage that any calculations were carried out. “It is just as important for us to understand the ‘why nots’ – the barriers and limitations – as it is to increase whole life carbon datasets of completed projects.” said Hrivnak, “It is only through collaborative data sharing, and being transparent about boundaries, that we can increase industry knowledge and collective improve the accuracy and precision of our predictions of the impact of the built environment.” •
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Erne Campus is world’s largest passive house premium building
outh West College’s new Erne Campus building in Enniskillen, Co Fermanagh, is the world’s largest, and the first educational building, to be certified to the passive house premium standard, the Passive House Institute has confirmed. The 8,200 m2 new build project is also the first building in the UK to achieve both passive house premium and BREEAM outstanding accreditations. Designed by Hamilton Architects and constructed by local firm Tracey Brothers Limited, the four-storey campus is fully funded by Northern Ireland’s Department for the Economy and will accommodate in excess of 800 full-time students, 2,000 part-time students and 120 staff when it opens in September. South West College chief executive, Michael McAlister, said: “From the earliest stages of planning, achieving sustainability and reaching the passive house premium standard has been central to the Erne Campus project. Achieving this accreditation is a significant milestone and one that we take great pride in. “Renewable energy and sustainability have been at the forefront of college delivery for several years, both in terms of the curriculum we offer to students and our own construction practices. The world-class Erne Campus will deliver a unique curriculum, education and a training programme specialising in
renewable energy and sustainability in a live working environment. We hope that in this way we can also advance sustainability in construction across these islands and beyond.” Meanwhile Tomás O’Leary, managing director of MosArt Architects and passive house consultant on the project, added: “I am delighted to announce the official certification of the recently completed Erne Campus at South West College, Enniskillen, as the world’s largest passive house ‘premium’ educational building. “The project sets a new standard for educational buildings across the globe in terms of energy efficiency, year-round comfort, and indoor air quality. It will act as a beacon and a source of inspiration for building designers everywhere in delivering on much-needed dramatic reductions in carbon emissions from the built environment.” Passive house ‘premium’ is an advanced version of the standard that requires buildings not only to meet the classic passive house standard for fabric efficiency and ventilation, but also to generate 120 kWh/m2/yr of renewable energy on site. •
Passive House Plus hosts online event
assive House Plus has hosted its first online event, a roundtable webinar on thermal breaks. The event, ‘Thermal breaks: freedom of architectural expression vs building physics’, was held on 8 June, and featured a number of the UK and Ireland’s leading experts on thermal bridging. Over 550 people registered for the event, which is available to view on the Passive House Plus YouTube channel. The event, which was sponsored by Farrat, kicked off with three PechuKucha style presentations: Passive House Plus columnist and Munster Technological University lecturer Dr Marc O’Riain traced the history of thermal bridging, before Enhabit associate director of building physics & PAS 2035 technical lead author Dr Sarah Price talked about thermal breaks in a retrofit context, and Elemental Solutions director Nick Grant drew from his experience on how to make a complicated subject like thermal bridging simple. The second session started with Bow Tie Construction director Rafael Delimata giving the contractor’s perspective, before PhD candidate Joe Pemberton & Will Swan of the University of Salford gave a joint presentation on the university’s research on thermal breaks, and Farrat commercial manager Chris Lister gave a presentation on the company’s proprietary thermal break solutions. The sessions were broken up by two roundtable panel discussions, which also included Pritchard Architecture RIBA client advisor and architect Ruth Butler, Build Collective director Tara Fraser, Wain Morehead Architects director John Morehead, Renfrewshire Council housing energy officer David Stevenson, and Architype technical associate Robert White. Passive House Plus surveyed the attendees after the event. Eighty five per cent of respondents said information from the event will probably or definitely influence decisions they take on construction projects. Passive House Plus ran the event as a pilot and is considering running further events in the future. To view a recording of the event, visit https:// bit.ly/3hjBMQl. • (below) A slide from Dr Sarah Price’s presentation indicates the significance of thermal bridging at windows in heat loss terms.
(above) Pictured at the new £30 million Erne Campus in Enniskillen are (left to right) South West College’s chief executive Michael McAlister, Northern Ireland economy minister Diane Dodds, and MosArt managing director Tomás O’Leary.
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Photo by Peter Cook/Passive House Institute
Passive house turns 30
Passive House Plus editor to speak at TEDx
he passive house standard is celebrating its 30th birthday this year. The world’s first passive houses were built in Darmstadt, Germany in 1991. They were designed by Swedish engineer Bo Anderson and the physicist Wolfgang Feist, who went on to establish the Passive House Institute, and who still lives in one of the Darmstadt passive houses today. In the autumn of 1990, diggers rolled into action and work began on a building site that had been allocated for "experimental construction" by the city of Darmstadt. The new homeowners moved into the terrace of four passive dwellings the following year. "Of course, I’m happy about this development: seeing the progress from the first experimental residential building to the projects and districts worldwide designed to the passive
house standard,” said Wolfgang Feist, on celebrating the standard’s 30th birthday. But he warned that, “without significantly greater commitment on the part of the governments, there will be very little progress in energy efficient construction of buildings.” He added: “The building sector must make a larger contribution. Many national construction standards still permit energy consumption that is much too high.” This year also marks both the 25th anniversary of the Passive House Institute and of the International Passive House Conference. For more information see www.passivehouseconference.org. • (above) The world’s first passive house scheme was built in Darmstadt in 1991.
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assive House Plus editor Jeff Colley will be speaking at the TEDx Tralee event on 15 October. With a working title of “Virtuous luxury: how green buildings can improve your life”, Jeff will be presenting the counter-intuitive case that, in the case of buildings, taking radical climate action can enhance rather than compromise quality of life. Sustainability will also be represented at the event by sustainable designer Chris Barrett, who will be drawing from his experience in biologically-inspired product design, integrating reclaimed and natural materials, and traditional musician Breanndán Ó Beaghlaoich, who will speak about the importance of enabling indigenous peoples to live off the land in their area in order to maintain their cultures. Other presenters at the event, to be held in the Siamsa Tíre Theatre in Tralee, Ireland, will include disability perception advocate Alan Carrigan; public relations consultant Anthony Garvey; human resource consultant Caroline McHenry; beauty therapist Christine Duff; motivational speaker Ciara McCullough; entrepreneur Colm O’Brien; social entrepreneur Edel Lawlor; television producer Grett O’Connor; life coach Jennifer Maher; artist and writer Kate Moore; philanthropist Ken Gibson; sports coaching developer Liam Moggan; writer, consultant, communicator, artist and advocate Nadia Ramoutar; and online educator Stephen Treacy. TEDx is a grassroots initiative, created in the spirit of TED’s overall mission to research and discover “ideas worth spreading.” For more information visit www. tedxtralee.ie. •
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Agar Grove, Larch Corner & Cranmer Road win at Passivhaus Awards
he redevelopment of Agar Grove by Camden Council in London was the winner of the large project award at this year’s UK Passivhaus Awards, which were held on 30 June. The 38-unit, seven-storey London apartment block was designed by the architecture practices Hawkins\Brown and Mae, with Architype providing passive house design. The scheme features a 50-50 mix of private and affordable housing. Agar Grove was featured in issue 31 of Passive House Plus, in which it was described as a “a model for sustainable urban regeneration and for creating liveable spaces at the
heart of our cities”. Larch Corner passive house in Warwickshire, designed by the architect Mark Siddall, won in the small projects category at this year’s awards. The house features a cross-laminated timber structure that is insulated with wood fibre insulation, and the Passivhaus Trust dubbed the 162m2 dwelling a “timber triumph”. Meanwhile, two new student accommodation buildings on Cranmer Road in Cambridge won in the people’s choice category. The King’s College scheme, also in cross-laminated timber, is featured in this
issue of Passive House Plus. It was designed by Allies and Morrison with Max Fordham providing passive house consultancy. All projects must be passive house certified in order to enter the awards. This year’s event was held online and coincided with London Climate Action Week. Winners were announced at the awards ceremony after all finalists presented their projects to an audience of almost 300 people. • (above) The 2021 UK Passivhaus Awards winners included (clockwise from bottom left) Agar Grove in the large project category; Larch Corner in the small projects category, and Cranmer Road student accommodation buildings in the people’s choice category.
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Growing use of CO2 monitors to slow Covid spread While the Irish government is delivering CO2 monitors to schools to help prevent the spread of Covid-19, and some European regions have mandated the use of such monitors in all buildings open to the public, the UK has yet to introduce such measures and has removed the requirement for mask-wearing in schools. By Kate de Selincourt
he Irish government is to provide CO2 monitors to all primary and secondary schools, and will support schools that need to upgrade their ventilation to help protect against airborne transmission of Covid. The announcement came as the US Centres for Disease Control (CDC) published research suggesting that increasing ventilation may reduce Covid infection in schools by as much as 35 per cent. Meanwhile, the UK government is under increasing criticism for failing to implement equivalent mitigation measures, and for actually removing the requirement to wear masks in schools in England, at a time when incidence of the highly infectious Covid Delta variant was rising more quickly among school age children than any other age group. The importance of ventilation and maskwearing in limiting Covid transmission in schools was highlighted by the findings from a US study. One hundred and seventy US schools responded to a survey about mask wearing, ventilation and air cleaning practices, and responses were compared against the official records for school Covid outbreaks, and against the community Covid incidence rates locally at that time. Around half the schools reported that steps had been taken to increase ventilation, and in these schools, there were 35 per cent fewer outbreaks. Air cleaning (for example via HEPA filtration) appeared to reduce the risk still further, to 48 per cent below the ‘no measures’ level, but numbers here were quite small, so this result is less clear. Mask wearing also showed a strong protective effect, with schools that required staff to wear masks reporting 37 per cent fewer outbreaks. The effect of mask wearing by children did not appear as strong. However, these schools were all primary age or kindergarten, and younger children may be expected find it hard to wear a mask effectively and consistently. i Irish schools In May, Ireland’s Department of Education announced that “to support schools... to
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identify rooms which may have inadequate ventilation and to optimise comfort levels” it would provide CO2 monitoring units over the coming months. These monitors are expected to flag when CO2 levels rise to anything above 800 parts per million (ppm), though the recommended “action level” is higher at 1,400 - 1,500 ppm. The use of CO2 monitors is seen as a simple way of showing how well a space is ventilated. Lack of fresh air ventilation in buildings is associated with increased spread of Covid-19 and super-spreader events. The department has advised schools to check that its ventilation is adequate, and if it is not, it will offer support to install or upgrade equipment. “Schools that identify inadequate ventilation in a room can utilise their minor work grant (for minor improvements) or apply for emergency works grant assistance to address ventilation enhancements on a permanent basis,” it said. A spokesperson for the department told Passive House Plus that it was finalising a traffic light type system “with the expectation of having three or four settings from 800 ppm upwards”. The accompanying guidance advises schools to increase ventilation in a room if CO2 levels rise above 1,400 ppm. This is the “action level” also recommended by the UK’s Scientific Advisory Group on Epidemics (SAGE). The Irish education department also cites SAGE advice that “A consistent CO2 value < 800 ppm (absolute value) is likely to indicate that a space is well ventilated, but does not mean that an environment is risk free of COVID-19 risks”. The move by the Irish government follows advice earlier in the year from the country’s Expert Group on the Role of Ventilation in Reducing Transmission of Covid-19. The group’s report recommended that schools should receive clear advice on ventilation, and that CO2 monitoring equipment should be made available. John Wenger, professor of chemistry at University College Cork and chair of the expert group, welcomed the announcement. He told Passive House Plus in an email: “I am delighted that the Department of Education
CO2 monitors in the classroom Cath Jones teaches in a typical English rural primary school – a Victorian stone building with high ceilings, and high windows, but no mechanical ventilation. To help prevent the spread of Covid-19, her school took matters into its own hands and bought a CO2 monitor. “After a conversation with friends about Covid and airborne transmission last autumn, I broached the idea of using a CO2 monitor with a colleague. He was fascinated by the idea and did some research of his own. “The school discussed the idea and the finance officer was asked to look into it. They found a relatively cheap monitor – quite basic. And we put it in the classroom. We set a level based on our reading around – though this was really used just as an indicator, we knew the monitor would not be that accurate. The upper limit we set was very rarely reached, in fact. “The windows were always open a little, but the kids in class were very observant, and when levels rose they would say ‘Sir, sir it’s going up’, and the windows would be opened more widely . “If levels hit our limit we had a ‘purge’: everyone would go outside for five minutes with all doors and windows thrown open, and return when CO2 levels in the classroom had gone back down close to ambient. “The class teacher was very happy, as social distancing is very difficult for us. The classrooms in our school are small: we were supposed to be maintaining two metre distancing but we physically could not do it. There are generally four adults in the classroom (as extra support for pupils) so the teacher felt this was a valuable additional protection measure.” The children (aged around eight to ten) really liked it, and took ownership, Cath found. “If a different teacher came in – for example, I take that class on one afternoon a week — the kids would point rising levels out to the visitor: ‘Miss Jones, do you think we should open the windows?’ It gave them a bit of responsibility, to check the levels, they really took to it.” Achieving this level of ventilation came at the cost of thermal comfort. “We were all in thermals until the end of May. It was perishing.” But Cath and her colleagues are sanguine about this, especially in view of the fact that Covid transmission in her school has, so far, not been reported at all.
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(DoE) in Ireland has responded positively to the recommendations contained in our reports. “The Group had a good level of engagement with the DoE, and are very pleased with the updated guidance on ventilation and especially the provision of CO2 monitors to schools.” He added that his personal advice is always to keep indoor CO2 levels below 800 ppm and to open more doors and windows to reach this level. But he added that it may not always be possible to achieve this, or achieve it comfortably, in a naturally ventilated building. The Teachers Union of Ireland also welcomed the move, but pointed out that the need for such measures had been clear to them and their members as early as the start of the academic year (September 2020). Summarising the results of a teacher survey, the union said last autumn: “Ventilation problems will now become critical as we move towards colder weather. Many schools, particularly those based in older buildings, will require new ventilation solutions and there will also be a need for monitors to signify when air exchange is required.” Hospitality Meanwhile, updated Covid guidance for the hospitality and leisure industries was also released in Ireland at the start of June by Fáilte Ireland, the national tourist board. As with the guidance for schools, businesses are advised what steps should be taken to increase ventilation. However, unlike in schools, and the hospitality sector in some other European nations (see ‘Scores on the doors’) Fáilte Ireland stopped short of recommending CO2 monitors. There is also considerable emphasis on cleaning regime. University College Dublin immunologist Dr Gerald Barry welcomed the new guidance. However, he told the Irish Times that he felt there was still insufficient emphasis on air movement, which he believes is “far more important in mitigation than Perspex screens or hand sanitiser”. UK guidance In the UK, the Delta variant of Covid was increasing faster in school age children than any other group at the time of writing, in mid-June. However, the government recently reversed its requirement for secondary school children in England to wear masks in school, and is not offering support either for CO2 monitors or for upgrading inadequate ventilation, despite numerous calls for it to do so. The UK’s Department for Education makes similar recommendations to those in Ireland on window opening and maximising fresh air flow though mechanical systems. However, although its advice refers to CIBSE guidance (which suggests CO2 levels be brought below 1,400 ppm), there is no specific suggestion that UK schools use
monitors to check ventilation effectiveness. Experts have been calling for school ventilation to be upgraded on a national basis, and for CO2 monitors to made available in UK schools. Professor Christina Pagel of University College London is one of many experts concerned about this inaction, especially in the light of what appears to be “significant transmission” of the Delta variant in UK schools. “We need to address this with mitigations in schools ASAP to stop disruption to education and wider spread,” she said on Twitter. Her view echoed an editorial on 1 June in the British Medical Journal by Dr Deepti Gurdasani, senior lecturer in epidemiology at Queen Mary University London, and colleagues. The editorial said that even at the time, it had been clear that removing the requirement for face coverings in secondary schools in England was ill advised “given the clear evidence for the role of children and schools in transmission of SARS-CoV-2 and the rise of the new variant”. The group added that as well as the re-instatement of masks, “there needs to be central investment in ventilation and air cleaning in schools, including CO2 monitors, and air filtration devices, to supplement ventilation where needed.” Passive House Plus asked if the UK government planned to follow the example of Ireland and offer support to schools to upgrade ventilation, and make CO2 monitors available, but the department did not respond specifically to this question. Some schools have independently purchased CO2 monitors [see ‘CO2 monitors in the classroom’], but their purchase and use is discretionary. Many UK schools are reportedly focusing resources on surface cleaning and hand sanitising instead. It is not clear exactly how much of the current spread of the Delta variant in the UK is occurring via school outbreaks, because detailed data is not currently being published by public health authorities in England. On 1 June, Citizens Advocacy Group and the data rights agency AWO took the first steps in a legal action against Public Health England, on the grounds that the agency was “acting unlawfully” in withholding data, and was “subject to political interference” in breach of its duty to protect public health.ii
i ' Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools — Georgia, November 16–December 11, 2020', Centers for Disease Control and Prevention, 28 May 2021 ii 'Covid-19: Government faces legal challenge over alleged suppression of school data', British Medical Journal, 2021; 373 (1 June 2021) iii 'A paradigm shift to combat indoor respiratory infection', Science, 14 May 2021, Vol 372, Issue 6543, pp. 689-691
‘Scores on the doors’– making CO2 monitors mandatory in public buildings Regulatory authorities around the world are being urged to follow the example of pioneering countries like Spain, Belgium and Canada, and require the display of live CO2 monitoring in buildings open to the public. In a joint letter in the journal Science, a distinguished international group of scientists say that visible, live displays of air quality should be a requirement for all premises open to the public. iii The 40-strong team, from disciplines including public health, infectious diseases, respiratory medicine, epidemiology and engineering, pointed out that there are strict controls on food, water and sanitation, in order to prevent mass outbreaks of dangerous infections. They warn that we are yet to take air quality as seriously, despite its obvious impact on the spread of deadly diseases such as Covid-19. “Wide use of monitors displaying the state of IAQ [indoor air quality] must be mandated. At present, members of the general public are not well aware of the importance of IAQ and have no means of knowing the condition of the indoor spaces that they occupy and share with others,” they write. “Visible displays will help keep building operators accountable for IAQ and will advance public awareness, leading to increased demand for a safe environment.” Regulation of air quality, and the requirement for publicly visible monitors, is now required in some countries. In Belgium, and a number of provinces in Spain, including the Balearic Isles and Asturias, businesses such as hospitality and indoor gyms are required to display a CO2 monitor, and to keep CO2 below a set level (in Asturias this is a challenging 800 parts per million). In North America, the focus is schools. For example, every classroom in Quebec will be provided with CO2 monitors to "ensure optimal indoor air quality". Meanwhile in New York, every room in every school has its ventilation assessed, and the results are displayed online.
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MARC Ó RIAIN
The emergence of thermal bridging & thermal bypass In his latest column, Dr Marc Ó Riain takes a look back at the some of the first projects to address the phenomena of thermal bridging and thermal bypass in buildings.
s I prepared for a roundtable talk on thermal bridging hosted by Passive House Plus, it got me thinking about the origins of thermal bridging, so I did a little digging. Like so much research in low energy buildings, the discovery of thermal bridging would come from Scandinavia in the mid-1950s and be developed further in the northerly latitudes of Canada in the 1960s, whilst thermal bypass would be defined by the ‘Princeton House Doctors’ in their ground-breaking retrofits of the late 1970s in the leafy suburbs of New York State. Research indicates that a working knowledge of cold bridging was part of Scandinavian construction prior to the 1950s. However, linear and point thermal bridging
The post-war brutalist movement saw an increase in concrete constructions in Europe, the UK and Ireland, with thermal bridging between internal partitions and slabs, and external walls, causing issues in most standard industrialised constructions well into the 1970s, before insulation was widely used. In a retrofit context, the oil crisis of 1973/74 saw the introduction of weatherisation and insulation grants, and a general interest in energy conservation. A group of academics in Princeton in 1977 would become the pioneers of building energy retrofit, and would establish the basis for internal thermal bypass as distinct from thermal bridging.
Heat transfer was carried both convectively in the block cavity and conductively in the continuous block mass. is first reported by Danish engineers Egeskjold and Korsgaard (who would later design the first zero energy house in Copenhagen in 1974) when examining moisture transfer in building envelopes. They had identified the risk of condensation particularly with continuous concrete intermediate floor slabs, and advised on using an internal cork insulation below the slab, and timber board above, to mitigate risk of damage or discoloration. They also identified that modern tighter concrete constructions were aggravating the risk of condensation at cold bridges. In 1963 Brown and Wilson, writing in Canadian Building Digest, warned that linear thermal bridges could cause condensation and structural damage in freeze thaw conditions, which can be “readily overcome where insulation is placed over the entire exterior”. They highlighted the impact of lateral heat movement in a non-continuous construction, such as a timber frame detail commonly found in the US and Canada at the time. There seemed to be a standard construction detail placing cork on the interior of timber studs or structural members to increase surface temperatures, which resulted in lateral heat movement from structural members toward the intermediate construction materials.
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The Centre for Environmental Studies at Princeton University retrofitted recently built houses in nearby Twin Rivers with a focus on space heating, water heating and air conditioning. “House Doctor” inspections analysed air infiltration, heat loss to insulated attics and non-insulated basements, conductive heat loss through heating pipes, heating controls, setpoints, passive solar and appliance heat gains, and payback periods. They used infrared cameras, thermal modelling, wind tunnel smoke tests, and one time air pressurisation with tracer gas (sulphur hexafluoride) to establish the rate of air change, which was ground-breaking in 1977. What was critical about the study was its examination of the performance of the inner building links to the unheated attic and basements. The team had modelled the expected temperature of the cold attic spaces, but their on-site inspection found them to be a far higher temperature, resulting in 35 per cent overall heat loss in winter. They discovered that the cavity in the party walls between houses was creating a thermal bypass. What they were highlighting was not a conductive heat loss (thermal bridge) but a convective heat loss as warm air travelled behind the stud and bypassed the attic insulation.
The team went to great lengths to seal the attic from living area and party wall. They simulated the mean temperature reduction in the attic after sealing, but soon discovered a discrepancy in the actual temperature reduction. Having resolved the convective heat transfer the researchers were left scratching their heads and looking for a parallel thermal transfer route. Eventually they rounded on the 200 mm hollow cinder blocks in the party wall that linked basements to inhabited floors to the attic. They discovered that the additional heat transfer was carried both convectively in the block cavity and conductively in the continuous block mass: thermal bypass and thermal bridging. In the next issue we will move to another Canadian project. The Conservation House in Saskatchewan was built in 1977 and is really the first time we see passive type principles beginning to emerge and coalesce in one project. n
References Brown, W. and Wilson, A., 1963. Thermal bridges in buildings. Canadian Building Digest, 08. 1957. Work of the Rationalisation Committee for Building Assemblies. Copenhagen: The Institution of Danish Civil Engineers. Birkeland, O., 1979. Energy losses through thermal bridges. Batiment International, Building Research and Practice, 7(5), pp.284-284. Socolow, R., 1978. The Twin Rivers program on energy conservation in housing: highlights and conclusions. Energy and Buildings, 1(3), pp.207-242.
Dr Marc Ó Riain is a lecturer in the Department of Architecture at Munster Technological University (MTU). He has a PhD in zero energy retrofit and has delivered both residential and commercial NZEB retrofits In Ireland. He is a director of RUA Architects and has a passion for the environment both built and natural.
01491 01491 836836 666666 firstname.lastname@example.org email@example.com www.cvcsystems.co.uk www.cvcsystems.co.uk
DR PETER RICKABY
Why the Green Homes Grant failed The Green Homes Grant scheme failed because politicians failed to heed more than a decade of lessons about how to do retrofit well, writes Dr Peter Rickaby, and now there will be an even bigger hill to climb.
ecently, I made a list of the UK government’s domestic retrofit programmes since before 2010. It’s not an exhaustive list, and doesn’t include programmes run by city authorities, but there are thirteen schemes on it. Most schemes had a fuel poverty focus or were aimed at social landlords. Five schemes were aimed at owner-occupiers, of which four failed or have been closed (notably the Green Deal). Among the five ongoing programmes are the regional retrofit supply chain pilots, the venerable Energy Company Obligation (ECO) scheme and new programmes for social housing and local authorities. Five schemes delivered individual improvement measures, two delivered multiple measures, and four promote whole-house improvement. Two more schemes are forthcoming. Against this scatter-gun background, the failure of the Green Homes Grants vouchers scheme is not surprising. Officials at the Business, Energy and Industrial Strategy department (BEIS) have been working with industry since 2009 to understand domestic retrofit, identify and manage risks, define what good retrofit looks like, and develop standards. We have had the Retrofit for the Future programme, Scaling Up Retrofit, the EU-funded Centre of Refurbishment Excellence (CoRE), the Greater London Authority’s RE:NEW programme, the ECO scheme, the Each Home Counts review and the development of the new domestic retrofit standard, PAS 2035. We have also had the Green Deal communities programme, the retrofit supply chain pilots and the Whole-House Retrofit competition. Slowly, the lessons from these schemes have been learned: the need to adopt a holistic, whole dwelling retrofit approach but prioritise the building envelope (‘fabric first’); the need to reduce demand before attempting to decarbonise building services; the need to pay attention to the corners, junctions, edges and interfaces, which are the places where retrofit goes wrong; that most retrofit risks are moisture risks; and the critical role of ventilation in protecting buildings and the health of occupants. To disseminate these lessons, we have the Futureproof programme and the Retrofit Academy. The Green Homes Grants vouchers scheme, announced in mid-2020 and closed less than a year later, was devised not by the BEIS officials
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who have supported and shared the learning, but by a team at 10 Downing Street and the Treasury, during the hegemony of Dominic Cummings. It was conceived not as a retrofit programme but as a post-pandemic job creation scheme. The budget was £1.5 billion, but the scheme delivered only £190 million worth of retrofit, and there is some evidence that the number of jobs in the retrofit sector went down. The scheme was poorly managed by a US-based company appointed because it was the only tenderer able to meet the start date. Householders had difficulty finding installers and getting their applications approved, and the installers themselves experienced such long payment delays that some were forced to withdraw. That is not all that was wrong. The Green Homes Grants vouchers scheme adopted a measures-based approach, despite all the lessons from the last ten years indicating that measures-based retrofit leads to poor outcomes, under-performance and dissatisfied customers, and that whole-dwelling retrofit is more effective and less risky. If retrofit goes wrong at the corners, junctions, edges and interfaces then those are the places schemes have to focus on, instead of letting thermal bridging, airtightness and ventilation issues fall into the cracks between measures. The industry, with BEIS’s encouragement, has been moving slowly from measures-based to whole-dwelling retrofit, and is scheduled to complete the transition by the end of June 2021, but the Green Homes Grants vouchers scheme ignored this process. Finally, although the new domestic retrofit standard PAS 2035 was published in 2019, there were not enough trained retrofit coordinators (a role required by PAS 2035) in 2020, so the Green Homes Grants vouchers scheme adopted an older, outdated standard, PAS 2030:2017, with less onerous requirements, and which is scheduled to be withdrawn in mid-2021. It emerged then that there were not enough installers certified under PAS 2030 to support the scheme. This is not the end of the story. Cancellation of the Green Homes Grants vouchers scheme in the run-up to the COP26 meeting in Glasgow in November is embarrassing for the UK government, who now need to put something better in its place, quickly. Promising deep reductions in emissions by 2035 without
a credible domestic retrofit programme is empty posturing. The predictable reaction of 10 Downing Street and the Treasury was to blame BEIS for this disaster, and BEIS, listening to installers’ complaints that the PAS 2030:2017 standard is too challenging (even though it has been required by ECO since 2017, and in earlier versions since 2011), pointed the finger at the national standards body BSI. To its credit, BSI responded that both PAS 2030:2017 and PAS 2035 arose from agreed recommendations of the Each Home Counts review, that both standards were developed by consensus of industry representative steering groups and subject to public consultation, and that BEIS had been a sponsor of, and active participant in, the process. As I write this, the word is that BEIS is to be reorganised and some people will be ‘moved on’ – so much for ten years of experience. As Gavin Killip of Oxford University has remarked, we have to disabuse politicians of the notion that retrofit is simple and that jobs can be created simply by throwing money at it. A little patience, listening to its own officials at BEIS, and going with the flow of the transition plan for standards and the training programmes for retrofit coordinators and installers, would have given 10 Downing Street and the Treasury a worldclass whole-dwelling retrofit programme that would have spent the £1.5 billion, reduced emissions and created jobs - but it seems politicians will never learn. Now we have a steeper hill to climb. n
Dr Peter Rickaby helps to run the UK Centre for Moisture in Buildings (UKCMB) and the Building Envelope Research Network at University College London. He also chairs the BSI Retrofit Standards Task Group and was technical author of the new domestic retrofit standard ‘PAS 2035: Retrofitting dwellings for improved energy efficiency — specification and guidance’. He is currently working on ‘PAS 2038: Retrofitting non-domestic buildings for improved energy efficiency — specification’. The views expressed here are his own and not necessarily those of UKCMB, UCL or BSI.
PER MONTH – OR £6 PER STUDENT FOR SPACE HEATING (Estimated, see ‘In detail’ for more) Building: Two graduate student accommodation buildings (1,091 & 435 m2), for 59 occupants Build method: Cross-laminated timber Location: Cambridge, England Standard: Passive house certification pending
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K I N G’S C O M F O RT CAMBRIDGE CHOOSES PASSIVE HOUSE COMFORT FOR KINGS’ COLLEGE STUDENTS
Most people think of cold, cramped and poor-quality buildings when they think of student accommodation, but two new passive house residences at King’s College, Cambridge are rewriting the rulebook, with their focus on occupant comfort, architectural quality, and an enlightened, long-term view of construction costs. Words by Anthea Lacchia
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ompleted at the end of 2019, Cranmer Road provides much-needed accommodation for the graduate students of King’s College at the University of Cambridge. The accommodation is located in West Cambridge, a ten-minute walk from campus, and includes two separate buildings: the three-storey Villa building, with 19 bedrooms, and the two-storey Stephen Taylor building with 40 bedrooms. This all-electric, passive house project was designed by Allies and Morrison Architects, with Max Fordham engineers providing passive house consultancy, as well as mechanical and electrical system design. The project was born out of a need for more student accommodation in Cambridge, says Shane Alexander, project manager and clerk of works at King’s College. “Prior to that, a lot of our graduates had to seek private accommodation within Cambridge,” he says. The passive house design ties in with the university’s aspirations to build sustainable housing for students and staff. “We’ve always wanted to get to the point where we would lower our carbon footprint and really focus on sustainability. Cranmer was really the first of many [projects] to head down that road,” Alexander says. The buildings, which were fully funded by a donor, sit west of the River Cam, at the heart of the West Cambridge conservation area, with its large houses and colleges, generous gardens and sports grounds. The architectural legacy of the area includes characteristic red-bricked villas designed in the late nineteenth and early twentieth centuries as part of the Arts & Crafts design movement. “It was a real uphill struggle to get planning permission to develop the site,” recalls project architect Matthew Traub. “It was only through a really careful consideration of the architectural heritage of West Cambridge that we developed proposals that were permissible by the local planning authority.”
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He says the design team perceived West Cambridge as having a dual character, with Arts & Crafts villas sitting alongside mid-20th century modernist university buildings. It is precisely this dual architectural language that inspired and guided the design of Cranmer Road. The Villa building, with its red brick facade, was designed as a contemporary response to the Arts & Crafts villas of the area, capable of sitting comfortably and “filling a gap in the frontage along Cranmer Road, where you have a consistent rhythm of Arts & Crafts villas,” says Traub. The Stephen Taylor building, with its exposed precast concrete structure and louvres
of glazed terracotta baguettes, responds to the more contemporary language of the university and college facilities, while subtly referencing the tones and textures of the Arts & Crafts buildings. King’s College specified a 100-year design life for the buildings, says Traub, and, while passive house was not a requirement from the start, it soon became “a really interesting opportunity,” he says. “The fact that it’s a comfort-driven metric was really important for the college,” he adds, as were the benefits in terms of energy use and sustainability. A lifetime cost assessment prepared by Faithful and Gould consultants highlighted a
2.3 per cent saving over 60 years across maintenance costs, operational costs, and cost of renewals with passive house, as opposed to no savings with a low energy approach or merely a regulations compliant approach. “When you combine that with the benefits in terms of the comfort of the space and consider a 100-year timescale, that was a really compelling case for the college to stomach the additional uplift in terms of capital costs for the long-term value of a passive house building,” Traub says. Indeed, there was an additional up-front cost to incur in building to the passive house standard, notes Alexander, for which there won’t be a return for about 35 years. However, “35 years in the lifespan of the college is nothing really,” he says. He estimates this cost uplift to be about £1.5m, or 10 per cent of the total project cost, and says this includes the cost of extra insulation, more thermally efficient windows and doors, PHPP modelling, and airtightness sealing. Cranmer Road’s interiors are bright, airy and spacious, with large common rooms and dual aspect kitchens. Four of the bedrooms are accessible to wheelchair users, an element the College was keen to provide. Other notable features include a wastewater heat recovery system in the shower drains, and openable window panels hidden behind terracotta baguettes in the Stephen Taylor building. Shutters can be added to the precast concrete structure along the south-facing corridor of the Stephen Taylor building to adapt to warmer conditions in the future. The structure and services of the building were also designed to be able to take an additional floor in the future. This was the first passive house project to occupy Gwilym Still, chartered engineer and passive house designer at Max Fordham building services engineers. “We had a practice-level interest in passive house, and I’d been interested in it for a while because it was one of the ways
Photos: Nick Guttridge
in which people talked about delivering really low-energy buildings,” he says. CLT with five plywood layers was the preferred structural solution and main air tightness line for both buildings at Cranmer Road. Airtightness was one of the main challenges, recalls Still, as it is evaluated through a single test which you either pass or fail, and which “tends to get everybody a bit scared.” Working with the design team and contractors, Still and his colleagues looked at different airtightness strategies, including using plaster, an external membrane, or the CLT itself for air-
The students liked the air quality, the design, the communal spaces, and the amount of daylight.
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King’s College specified a 100-year design life for the buildings.
tightness. “We settled on either the CLT or the membrane because we wanted to have something that we could test fairly early on in construction, and went for the CLT itself because it seemed like a more robust choice.” Structural engineers Smith and Wallwork, who have extensive experience with CLT, also played a big part in designing the airtightness strategy. “The sequencing was set out so that we could get the primary structure and the windows in early on [...], when the whole airtight envelope was still accessible, [in order to ensure] tests could be done and any issues could be fixed early,” Still says. CLT joints were taped with tapes from Pro Clima, and the damp proof membrane in the ground was lapped onto the base of the CLT. The team opted for an all-electric heating system because decarbonisation of the national grid is likely to take place over the lifetime of the buildings, says Still, rendering electricity a lower carbon fuel source than gas. Simplicity was also key guiding principle in the project. “We were generally trying to keep the systems as simple as possible,” says Still. “Having electric panel radiators is a really simple and fairly cost-effective way of delivering low-carbon heat into the buildings,” he explains. Heating storage was kept to a minimum and the water heaters are all very close to the outlets, with pipework between the water heaters and the showers kept as small and short as possible.” Too much pipework for hot water can create a risk of overheating in a passive building, especially when you factor in future climate change. This was one of the reasons why a point of use system for hot water — where water is heated close to where it is used - was chosen. Still combined meter reading data and software modelling to study energy consumption and heating in the buildings. Metering data shows that domestic hot water consumption is the highest energy draw within the building. Both buildings use mechanical ventilation with heat recovery, and post-occupancy feedback on summer comfort has generally been positive. Since completion, the buildings have been through two winters. The Passive House Planning Package (PHPP) models assured the team that buildings would perform well in cold weather. Measured heat load, the amount of heat energy a building needs to maintain 20 C on the coldest day of winter, was 8 W/m², lower than the passive house target of 10 W/m². According to Still, heat load is a particularly good indicator of the thermal performance of the building envelope, because it is less influenced by changes in the thermostat setpoint than the other key metric of thermal performance, space heating demand. “We also have longitudinal data showing that, once the buildings were occupied, some of the heating demand was higher than expected,” says Still. Specifically, the PHPP software indicated that space heating demand,
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CONSTRUCTION IN PROGRESS
1 The ground floor features an unbroken raft of 200 mm Cellecta Hexatherm Xfloor 500 insulation; 2 aerial view of the site, with concrete slab in place and work commencing on the CLT structure; 3 & 4 construction of the CLT frame underway; 5 CLT joints taped with pro clima tapes, and installation of the Internorm triple glazed timber-aluminium windows; 6 installation of the BauderTEC KSD vapour control layer to roof featuring CLT dormers; 7 wall build up featuring brick externally, followed behind by drained cavity, Knauf Earthwool rainscreen slab, and pro clima Solitex breather membrane; 8 ventilation in the Stephen Taylor building is provided by Airflow MVHR systems, supplemented here by an electrical heating coil to boost temperatures when necessary; 9 a blower door test under way; the buildings scored 0.16 and 0.19 air changes per hour.
the amount of active heating input required to heat a building over a year, was higher than the threshold of 15 kWh/m²/yr for one of the buildings: 13.1 kWh/m²/yr for the Villa building and 17 kWh/m²/yr for the Stephen Taylor building. This is possibly because the PHPP models are based on the whole building being at 20 C,”and we know that the students have overridden the thermostats to make their spaces warmer,” says Still. If you turn the heating up by about two degrees, the annual heating energy consumption goes up by about a third, so “it’s fairly sensitive to that change”, he says. Post occupancy evaluation was conducted with all students who have lived in the buildings. “Generally, feedback was very positive,” says Still. The students liked the air quality, the design, the communal spaces, and the amount of daylight. Points raised by the students included that they wanted more control over the
heating, feedback that is now being fed into a subsequent project for King’s College, and that the lights inside the bathrooms turned off after about 20 minutes, which was too short a period. This has now been adjusted. The students were involved right from the project’s outset. “We do that with all our projects,” says Alexander. For instance, as a result of consultation with the graduate community, the bedrooms in the Villa Building are not ensuite. “[For the students,] it was quite important to have a range of price points for accommodation. Some people want cheaper rent and are quite happy to share a bathroom,” explains Traub. Students also asked for a choice of carpet or hardwood floors being offered: “not everyone wanted carpets because some people suffer from allergies,” explains Alexander. The result of all these design and consultation efforts is a space where college life can
blossom. “King’s wanted to create a unified space for graduates to come together, learn together and feel like they play a part in the life of King’s College,” says Traub. Enjoyment of the outdoor spaces is a key part of college life, so a lot of thought went into the green spaces around the buildings, he explains. The gardens include pleached trees and allotment planting spaces for students, and the shared garden is split into a formal lawn and a meadow that accommodates more biodiversity. There is also a woodland with retained tree cover and a swale on the grounds. Cranmer Road went on to win the 2021 Cambridge Design and Construction Award for best new building over £2 million, as well as the sustainability and engineering prize at the same event. “The college is really pleased with it,” says Alexander, “to the extent that as soon as we started Cranmer Road we were already
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working on another [student accommodation] project, Croft Gardens, which will also be fully passive house certified.” “The students who moved into Cranmer absolutely loved the buildings,” he says, noting that “different groups of students have lived there now, and there’s never been a negative word said about the accommodation.” “We’ve learned a lot through the scheme,” says Still, “from airtightness, to structure design, ventilation, detailing, and proper insulation of the ventilation ductwork – we’re already applying our learnings in current projects.” “Quite different from the student accommodation I remember living in!”
SELECTED PROJECT DETAILS Client: King’s College, Cambridge Architect: Allies and Morrison Main contractor: RG Carter M&E engineering: Max Fordham, Ingleton Wood Passive house consultant: Max Fordham Structural engineering: Smith & Wallwork Project management: Faithful & Gould Quantity surveyors: Faithful & Gould Landscape architects: LDA Design Planning consultants: Turley Mechanical contractor: Munro Airtightness products: Ecological Building Systems CLT structure: KLH Primary wall insulation: Knauf Thermal wall ties: Ancon Teplo-L-ties, via Leviat Floor insulation: Cellecta Windows & doors: Internorm MVHR: Airflow & Zehnder Wastewater heat recovery: Recoup Electric underfloor heating: Raychem Electric radiators: Adax
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GARDEN BUILDING The passive house environmental strategy employed at Cranmer Road necessitates a careful approach to the design of the external fabric: engineering to minimise heat loss, reduce energy consumptions and consequently reduce carbon emissions. This fabric first approach is not immediately apparent when you see the building, balancing performance with aesthetics to deliver a quietly innovative and highly sustainable graduate campus. 1. Floating foundation: A foundation system that literally ‘floats’ the building on a thick layer of rigid insulation, ensuring that no heat is lost into the ground. 2. Structurally independent skin: The external cladding is hung from a structurally independent pre-cast concrete frame, minimising penetrations through the insulation to avoid unnecessary heat loss. 3. Triple glazed windows: Glazing that minimises heat loss and avoids cold spots around the windows. 4. Continuous insulation: A thick layer of insulation is maintained around the external envelope.
5. Airtight structure: A cross laminated timber structure with low embodied carbon doubles as the structure and primary airtight envelope. Minimising heat loss through escaping air by achieving an airtightness of 0.19 ACH.
6. Deep window reveals: Deep window reveals reduce the chances of overheating within the building. 7. Insulated roof: A layered roof build-up minimises heat loss by maintaining a continuous layer of rigid insulation.
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Harris Academy School Sutton, the first Passivhaus secondary in the UK. The 2020 winner of Education Estates’ Architect of the Year, CIBSE Project of the Year.
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ecologicalbuildingsystems.com 30 | passivehouseplus.co.uk | issue 38
Ecological brands used: Gutex, Pro Clima, Bosig, Wellhöfer
IN DETAIL Building type: Two graduate student accommodation buildings built with cross-laminated timber. Villa Building: 435 m² (treated floor area). Stephen Taylor Building: 1,091 m². Location: Cranmer Road, Cambridge, CB3 9BL Completion date: December 2019
buildings combined over the first five months of 2021, though the Covid pandemic may have affected occupancy patterns. This includes all standing charges but not VAT. Projection of space heating costs using PHPP figures estimates that the average monthly cost for space heating only will be £85 for the Villa Building and £279 for the Stephen Taylor Building, exclusive of both standing charges and VAT.
Project cost: £14,694,0000 Passive house certification: Pending Space heating demand (PHPP): Villa Building 13.1 kWh/m²/yr, Stephen Taylor Building 17.0 kWh/m²/yr Heat load (PHPP): Villa Building 8.2 W/m², Stephen Taylor Building 8.8 W/m² Primary energy renewable (PHPP): Villa Building 80.8 kWh/m²/yr, Stephen Taylor Building 75 kWh/m²/yr Primary energy non-renewable (PHPP): Villa Building 188 kWh/m²/yr, Stephen Taylor Building 171 kWh/m²/yr (figures are high because the building is all electric). Heat loss form factor (PHPP): Villa 2.4, Stephen Taylor 2.4 Overheating (PHPP): 0 per cent of year above 25C Number of occupants: Villa Building: 19, Stephen Taylor Building: 40 Airtightness (at 50 Pascals): Villa Building 0.16 ACH, Stephen Taylor Building 0.19 ACH Measured energy consumption: All electricity boards are metred in high resolution. Understanding exactly how much energy is used within the buildings has been complicated by a global pandemic. Figures are based on monitoring from January to April 2020. Monthly energy use for each of domestic hot water, kitchens, lighting, plant, small power, and miscellaneous items was consistent during this period, so these figures were extrapolated over a whole year. Initial monitoring showed a delivered energy use intensity (EUI) of 51 kWh/m²/yr across both buildings. This was reviewed later in the year, after client feedback that some of the occupants had overridden the temperature control on the radiators. The total EUI had risen to 71 kWh/m²/yr, which included metred space heating usage. The assessment included the superstructure, substructure, external and internal walls, glazing, staircases, and finishes to walls, ceilings and floors, but does not include mechanical and electrical equipment. Energy bills (measured or estimated): Electricity bills, covering all energy use, averaged £2,202 per month for the two
Thermal bridging: CLT was used as primary structure, with a raft foundation for both buildings. Rawlplug fixings to hold insulation against CLT. Low-conductivity brick ties were used (Ancon Teplo L-Ties). Overall thermal bridging figures are: Stephen Taylor Building: 1.6 kWh/m²/yr. Calculated from PHPP at 0.0080 W/m²K (m² of total thermal envelope) Villa building: 3.7 kWh/m²/yr. Calculated from PHPP at 0.019 W/m²K (m² of total thermal envelope). Embodied carbon: An analysis was carried out of the embodied carbon of the buildings by Allies and Morrison using an in-house tool the firm developed. It only included life cycles stages A1 to A3 (raw material supply to manufacturing), so did not include the construction process itself, transport to site, or the use phase or end of life. It produced the following results: Gross embodied carbon values: Villa building: 390.5 KgCO2eq/m², Stephen Taylor building: 392.5 KgCO2eq/m². Gross embodied carbon values incorporating carbon sequestration of the CLT: Villa Building (A1-A3): 110 KgCO2eq/m², Stephen Taylor building (A1-A3): 134.1 KgCO2eq/m². The analysis includes superstructure, substructure, external walls, glazing, internal walls, floor, ceiling and roof finishes. It does not include mechanical, electrical and plumbing services. Ground floor (both buildings): Concrete slab on an unbroken raft of 200 mm Cellecta Hexatherm Xfloor 500 (2 x 100 mm layers of insulation, shiplap joints, joints staggered). 900 mm strip foundation at the perimeter. U-value 0.167 W/m²K Walls (typical) Villa Building: Brick externally, with a 75 mm drained cavity, 225 mm Knauf Earthwool rainscreen slab, pro clima Solitex breather membrane, CLT structure (120 mm), timber stud 40 mm deep with 25 mm Rockwool to inner face, 15 mm unventilated air gap, 30 mm plasterboard internally. U-value: 0.115 W/m²K
counter-battens generally, on pro clima breather membrane, on 160 mm Kingspan Kooltherm PIR insulation, on vapour control layer, on 100 mm CLT structure, on 50 mm mineral wool, on 50 mm unventilated timber studs, on 25 mm plasterboard internally. U-value: 0.11 W/m²K Stephen Taylor Building: Brown roof generally followed underneath by 130 mm EPS insulation, 200 mm PIR insulation (Innobond), vapour control layer, 100 mm CLT structure, 50 mm mineral wool, 70 mm unventilated air gap (timber & aluminium studs), 25 mm plasterboard. U-value: 0.06 W/m²K Windows & external doors: Generally, Internorm HF310 triple glazed timber-aluminium windows throughout both buildings. Internorm AT200 aluminium entrance doors & Internorm HS330 Internorm HS330 triple glazed timber-alu life-and-slide doors. Roof windows: Gorter glazed roof hatches to Villa building with HR+++ triple glazing. Gorter RHTEP insulated roof hatches to Stephen Taylor building. Heating system: Generally, Adax Neo Stylish electric panel radiators through both buildings, plus electric towel rails to bathrooms. Electric underfloor heating to the common room in the Stephen Taylor building. Electric panel radiators in each bedroom have in-built controls, including thermostat, timeclock, and open window detection functionality. Electric towel rails in ensuites have push-button which lets the heater run for a limited time period. Electric underfloor heating in Stephen Taylor building is controlled by local thermostat. Ventilation Villa building: 2 x Zehnder ComfoAir Q600 units, Passive House Institute certified efficiency 87 per cent. Stephen Taylor building: 10 x Airflow DV Entro 400 units, Passive House Institute certified efficiency 88 per cent. 3 x Zehnder ComfoAir Q600 units, certified efficiency 87 per cent. Water: Low flow sanitaryware – 6 l/min showers. Wastewater heat recovery from Recoup.
Stephen Taylor Building: Precast concrete and brick externally with a 60 mm drained cavity, 240 mm Knauf Earthwool rainscreen slab, pro clima breather membrane, CLT structure (120 mm), timber stud 40 mm deep with 25 mm Rockwool to inner face, 15 mm unventilated air gap, 30 mm plasterboard internally. U-value: 0.115 W/m²K Roofs (typical) Villa Building: Clay tiles on battens &
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D U N D E E PA S S I V E H O U S E
PER MONTH FOR ALL HEATING, HOT WATER AND ELECTRICITY Building: 181 m2 detached dwelling Build method: Timber frame Location: Dundee, Scotland Standard: Uncertified passive house
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D U N D E E PA S S I V E H O U S E
P I TC H PERFECT BEGUILING DUNDEE PASSIVE HOUSE PUTS WOOD INTO WOODLAND
An intriguing new passive house in Dundee takes the traditional ‘box’ form associated with the standard and turns it on its head, using a series of pitched roofs and different claddings to make it feel more like a traditional city terrace than a single dwelling – built with a heavy emphasis on carbon sequestering materials. Words by David W Smith
enton House lies in a little oasis of beautiful old woodland in suburban Dundee. It is around 10 minutes by bike from the city centre, in the former grounds of Invergowrie House, a turreted fort built between the fourteenth and sixteenth centuries. From the second storey of this upside-down passive house there are wonderful views over the top of the wood and the surrounding cityscape, to the ever-changing light of the Tay Estuary. For owners David and Jenny Arrenberg, the warmth and comfort of Fenton House makes a welcome contrast with the freezing cold flat they previously occupied in Invergowrie House. “Living in Fenton House is ‘pinch yourself’ time,” says David, who works as an engineer for Scottish Water. “Before we started to build, I used to climb the trees to make sure we’d be able to see into the distance from the top floor. We can! The views of the river are gorgeous. There are lots of tidal changes and
you get sand banks one minute and it’s choppy the next. We can see as far as Kinnoull Hill in Perth.” As for the warmth, David spent a lot of the winter Covid-19 lockdown working from home in shorts and a T-shirt. “Our north-facing flat in Invergowrie House was the exact opposite. It was a converted storage room on the ground floor and slightly underground. There were zero passive house principles involved and it was freezing in winter. The difference with Fenton House is about 20 degrees!” The joy, however, is tinged with sadness. David’s father was a major inspiration for the project, but he passed away before it broke ground. “Dad was a man of many trades, an officer in the navy, a tree surgeon, and a picture framer, but he went on to become a plumber and builder. His talent as a tradesman was painting and stenciling — he was a very creative chap,” David says.
His father had always encouraged David to convert the plot of land — gifted by his aunt — into a permanent home. “To say I am disappointed he didn’t get to see the house is an understatement. I think about it daily. My dad always wanted to build his own house, but never had the money. He used to go on at me about building on the plot. And we worked on the woodland together with my brother from when I was nine years old. I kept finding reminders of him around the land, old bottles, tools and materials. His memory drove me on to do a good job when the work was hard,” he said. David is not native to Dundee, or Scotland. He was born in Bromley North, in London, and moved up with his English parents in 1987 when he was three and his brother was eight. He soon adopted the local accent, whereas his older brother has retained a London twang. The family lived in Invergowrie House, which
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D U N D E E PA S S I V E H O U S E
Living in Fenton House is ‘pinch yourself’ time.
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was split into four flats with the attached land divided between the owners. His aunt and uncle occupied the most spacious flat and had the largest, seven-acre plot. In 2003, after the death of her husband, his aunt went to live in Herefordshire. But she kept hold of about three acres of the land, with its magnificent 250-year-old cedars and oaks. Given David wanted to live in Dundee, and his keen interest in building a home, his aunt decided to offer him the land and the opportunity to build here. In 2015, David and his wife Jenny moved into the ground-floor flat at Invergowrie House. In the same year, they hired Kirsty Maguire, a Dundee architect specialising in the passive house standard, to design their home. They already had some clear ideas. They wanted an open-plan living space upstairs to take advantage of the views. The couple also wanted a low energy house. David’s civil engineering background meant he was knowledgeable about sustainable design. “The open plan could have made it feel a bit cavernous, lacking in character and over-reliant on the great views. But I designed a series of four pitched roofs,” said Kirsty. “The dining space, living room and kitchen are each defined volumetrically by the vaulting of the roofs. It gives them the feel of semi-separate rooms. Basically, we kept to a simple rectangular box — which was great for achieving passive house and cost management — but invested in a more complicated roof.” Each of the apexes has a glulam beam and an airtight layer that goes over the top of it. “You have to make sure the airtightness membrane is in place as you build, as it exposes the
glulam beams. They are very beautiful and part of the expression of the space. But it needs to be carefully thought out and installed,” said Kirsty. She specified low carbon materials, including wood-fibre insulation and a timber structure. The insulation came from Steico, and Kirsty said that she specifically chose wood-fibre due to its decrement factor — the time it takes for a peak daily temperature outside to become a peak daily temperature inside. Wood-fibre is better at controlling this decrement factor than lighter synthetic insulations, thus helping to prevent overheating. For the cladding, Kirsty chose Scottish larch and recyclable long-lasting zinc. Meanwhile, an air source heat pump was installed to provide constant hot water. The house was also equipped with an MVHR system, photovoltaic panels, and electric infra-red panels for space heating. Although the plans were submitted in 2015, getting approval was a slow process. The exact location of the house had to be moved a little after neighbours on the adjacent housing estates expressed concern that it would overlook their properties. David also had to put in place a woodland maintenance plan to ensure the protection of the mature trees. Another issue was fire engine access, which the council deemed essential. Meanwhile, David and Jenny were not even ready to begin immediately. They were busy scraping together all the money they needed to pay for the project. The total cost ended up at around £330,000, including Kirsty’s fee. Work eventually began in May 2018 and took a year to complete. The contractor, Craigs
Eco Construction from Linlithgow, had experience building passive houses and offered a flexible way of working that left David free to find cheaper prices for much of the work. “I hired plasterers, electricians and plumbers directly and Craigs Eco were happy to work with them. It saved quite a lot of money,” he said. Even greater sums were saved by David’s relentless bargaining over materials. “I was pretty ruthless when it came to bartering down prices. The zinc looks tremendous, but the original quote was for £95,000. I ended up getting it down to £54,000. My Excel spreadsheet never left my side and I reckon I saved over £60,000 arguing over quotes and going round and round in search of cheaper suppliers,” he said. With his flexible working hours, and home base at Invergowrie House, David was able to act as a second project manager. He carried out his own quality checks and was available if Craigs Eco could not be on site first thing in the morning. Working for Scottish Water proved useful as he personally knew the water and sewage engineers that worked on the house. One of the most joyful moments came when the Polish joiners put together the wooden frame on site. “It would have been tricky to build it off site and then crane it in as there wasn’t a lot of space. They constructed the ten massive panels on the foundation slab, then we pulled them into place with a crane. They all slotted together like Lego, and it was one of the most fun things I’ve ever seen. The joiners only spoke broken English, but they worked overtime and I was so impressed I gave them a
Photos: David Barbour
bonus of a bottle of whisky and a wood-turning machine,” David said. The construction process went smoothly, and the couple moved into the house in June 2019, with baby Ruby who was born at the start of the construction process. There was still work to do furbishing the house with contemporary designs, which Jenny had lots of ideas about. But right from the start, living in Fenton House was an almost surreal experience of comfort and spaciousness after four years in a cold basement flat. Even during lockdown, with the entire family at home, bills have been low. “Our electric bills were about £1,200 for the year and we are running an electric car, an electric mower to cope with gardening on an industrial scale. And Jenny, who is a partner in a dental practice, has been running three loads of the washing machine every day of the week because of all the PPE gear. Heating has cost virtually nothing,” said David. Having the bedrooms on the ground floor makes them slightly cooler, but David and Jenny like it that way. On the rare hot Dundee days, the building’s natural ventilation is able to cool the house. Opening the roof lights can draw air through the whole building. The sliding patio doors are another option. The house is also set up to meet accessibility requirements. It could be retrofitted with a stairlift and there is space for wheelchair storage. Kirsty says it would even be possible to set it up as a ground-floor flat only. The couple have no plans to move anywhere else. “David is planning to be carried out in a box,” she said.
D U N D E E PA S S I V E H O U S E
David believes Fenton House will be a magical place for his children (the couple had another baby just as Passive House Plus went to print, after we interviewed David for this article). He has built a large climbing frame, but when they tire of that, there are all the mature trees to climb. Deer and foxes are seen daily. “I couldn’t imagine a better house for a family. Ruby is the jammiest kid in Dundee and the next child will be even luckier. We get loads of people coming to visit, and it inspires them to think about building their own passive houses.”
I designed a series of four pitched roofs.
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D U N D E E PA S S I V E H O U S E
n analysis of the building’s whole life carbon score was conducted by John Butler Sustainable Building Consultancy, using PHribbon. Based on a cradle-to-grave analysis, the building totalled 496.8 kg CO2e/m2 GIA – a total which in large part reflects the fact that the analysis assumes the stored CO2e from the timber and timber-based products is released after sixty years (the standard lifespan for the assessment, in line with the RICS whole life carbon methodology.) From cradle to practical completion, however, the building has a total of 353 kg CO2e/ m2 GIA, with a further 216 kg CO2e/m2 stored in the timber and timber-based products at that point. The analysis also compared the as-built external walls against a cavity wall version to the same spec. The as built walls showed a small reduction compared to the cavity wall when considered on a cradle to grave basis, from 221 kg CO2e down to 194 kg CO2e/m2. But at practical completion, the difference is far more marked: 224 KG CO2e down to 154 kg CO2e – and with 131 kg of stored CO2e in the as-built walls, versus just 15 kg in the cavity walls. The analysis included the external envelope, internal walls, floors, and finishes. The stairs were excluded, as was the balcony, and the only internal fixtures included are the sinks/basins/WCs. Due to the absence of environmental product declarations for the heat pump, MVHR system and ductwork, data from the closest comparable certificates was used, drawing from the Product Environmental Passport database – albeit with data for stainless steel ductwork instead of the polypropylene ductwork that was used. The analysis assumed no replacements of building fabric during the projected sixty-year life
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but assumed three replacements of the hot water heat pump, two replacements of the hot water pipes, sanitary ware and sinks, and one replacement of the PV array and MVHR system. The radiant panels and electric towel rails weren’t included, due to lack of data. The entire superstructure of internal and external walls and roof (and window frames, excluding any aluminium cladding) is made from timber and timber-based products, so it’s perhaps unsurprising that they represent the largest chunk of embodied carbon in the building, at a combined total of almost 84 kg CO2e/m2 – though they also provide over 216 kg of sequestered CO2e, meaning these materials store more than 2.5 times as much CO2 as their manufacturing process emitted – at least for as long as they remain in the building. The next largest chunk of emissions is the zinc cladding and roofing at almost 57 kg CO2e/m2, followed by the PV at 50 kg CO2e/m2, and the concrete from the foundations at 38 kg CO2e/m2, with inert products – including glazing, plasterboard, plaster and ceramics – at 34 kg CO2e/m2, with over 39 kg CO2e/m2 relating to bringing materials from the factory gate to the site. Much of this is specific to the concrete – over 42 per cent of that figure is associated with the concrete supply. A treemap lays the cradle to grave figures bare: building-related services, including the PV array, the hot water heat pump and MVHR system, represent 27 per cent of the total, with the roof, external walls and substructure at 20, 18 and 16 per cent respectively. Although triple glazed windows have been criticised as being too high an embodied carbon cost by some high-profile life cycle assessment experts, in this case the total for windows, doors and rooflights only reaches 5 per cent of the total.
Embodied Co2e Comparison: Cradle to Grave, External Walls Only 120 100 80 60 40 20 0 -20 -40 -60 Cavity As Cavity As Cavity As Cavity As Wall Built Wall Built Wall Built Wall Built
Module A: Concrete Module A: Inert Module A: Oil Based Module A: Zinc Module A: A4 Transport to Site Module A: A5 Construction Module A: Aluminium Module A: Brick Stored CO2: Timber Stored CO2: Timber Based Module C: Demolition & Disposal
D U N D E E PA S S I V E H O U S E
CONSTRUCTION IN PROGRESS
1 Insulated raft foundation to minimise thermal bridging; 2 the timber frame sections being craned into place, with baby for scale; 3 Steico wood fibre batts, seen here waiting to be installed, were used throughout the walls and roof to insulate the I-joists; 4 while Steico wood fibre boards were used externally on the roof and walls; 5 each of the roof apexes has a glulam beam and an airtight layer above it; 6 airtightness membrane to walls and roof, and taping around thermally broken windows; 7 a blower door airtightness test being carried out; 8 & 9 plywood was installed over the Steico wood fibre board on three of the four sections, with zinc cladding then attached to the plywood, while the fourth section was clad with larch.
ph+ | dundee passive house case study | 37
D U N D E E PA S S I V E H O U S E
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38 | passivehouseplus.co.uk | issue 38
D U N D E E PA S S I V E H O U S E
SELECTED PROJECT DETAILS Client: David & Jenny Arrenberg Architect: Kirsty Maguire Structural design: Burnett Consulting Engineers Passive house designer: Kirsty Maguire Main contractor: Craigs Eco Construction Ventilation: Paul Heat Recovery Scotland Air source heat pump: Luths Services Windows & doors: Green Building Store Wood fibre insulation: Steico Airtightness testing: Thermal Image Scotland Insulated foundation: Advanced Foundation Technology Roof windows: Fakro Zinc cladding: HL Metals Flooring: West End Flooring Lighting: Terkan
WANT TO KNOW MORE? The digital version of this magazine includes access to exclusive galleries of architectural drawings. The digital magazine is available to subscribers on passivehouseplus.ie & passivehouseplus.co.uk
ph+ | dundee passive house case study | 39
D U N D E E PA S S I V E H O U S E
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40 | passivehouseplus.co.uk www.cupapizarras.com
| issue 38
D U N D E E PA S S I V E H O U S E
IN DETAIL Building type: 181 m detached two-storey timber framed house. 2
Location: Dundee, Scotland Completion date: May 2019 Budget: £330,000 approx, including all fees Passive house certification: Not certified Space heating demand (PHPP): 15.5 kWh/ m2/yr (PHPP carried out at design stage) Heat load (PHPP): 11.2 W/m2 Primary energy renewable (PHPP): 55 kWh/m2/yr Primary energy non-renewable (PHPP): 110 kWh/m2/yr Heat loss form factor (PHPP): 3.27 Overheating (PHPP): 0 per cent of the year above 25C Number of occupants: 4 Environmental assessment method: N/A Airtightness (at 50 Pascals): 0.66 m3/hr/m2 Energy performance certificate (EPC): A 93 Measured energy consumption: 6,697 kWh or 37 kWh/m2 (August 2019 to August 2020, measured electricity consumption).
Thermal bridging: Insulated raft foundation to minimise slab edge thermal bridge; I-joist construction with continuous wood fibre external insulation around all walls and roof to minimise thermal bridges; acrylic fixings for external wood fibre insulation; over-insulated window frames; thermally broken windows; thermal bridges designed out as far as possible through overall design. Valley gutters over-insulated to minimise thermal bridges. Energy bills (measured): £1,425 per year, for all electricity (includes space heating and hot water). This includes charging an electric car and electric mower for the grounds. Minus an average annual feed in tariff of £150 gives a net energy bill of £1,275 per or £106 per month. Ground floor: 150 mm compacted base, followed above by 25 mm sand blinding, 1 mm damp proof membrane, 250 mm EPS insulation, 200 mm reinforced concrete slab, floor finish. U-value 0.124W/m2K Walls: Zinc or timber rainscreen cladding, followed inside by 50 mm ventilated cavity, 100 mm Steico wood-fibre board, 240 mm I joists stuffed with Steico wood-fibre batts, 12 mm OSB, Intello Plus airtightness membrane, 50 mm services cavity with softwood battens, plasterboard. U-value 0.115 W/m2K Roof: Zinc roofing, on 22 mm softwood sarking boards, on 50 mm ventilated cavity with 50x50 mm softwood boards, on 100 mm Steico wood-fibre board externally, followed beneath by 240 mm I joists stuffed with Steico wood-fibre batts, 12 mm OSB, Intello
Plus airtightness membrane, 50 mm services cavity with softwood battens, plasterboard. U-value 0.116 W/m2K Windows & external doors: Green Building Store Progression triple glazed windows. Passive House Institute ‘A’ certified component. Standard whole window U-value: 0.68 W/m2K. Green Building Store Ultra doors. Roof windows: 3 x Fakro U8 triple glazed roof windows. U-value: 0.8 W/m2K Heating system: Ecocent Ambient air source heat pump for water heating only with 300 litre integrated cylinder. Space heating provided by Trotec infrared panel heaters and low wattage towel rails. Ventilation: Zehnder ComfoAir Q350 heat recovery ventilation system. Passive House Institute certified to have heat recovery rate of 90 per cent. EN 308 certified efficiency of 93-96 per cent. Water: Rainwater soakaway as opposed to connection to sewer. Electricity: 3.99 kWp solar photovoltaic array, ground mounted. Provides electricity to general household supply with any excess exported to the grid. Green materials: Wood fibre insulation for all floors and walls, timber cladding (heat treated larch), fully recyclable zinc cladding, insulated foundations, glulam beams, locally sourced timber frame.
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PER MONTH FOR SPACE HEATING & COOLING (Estimated, see ‘In detail’ for more) Building: 223 m2 uncertified passive house Build method: Timber frame Location: Limerick, Ireland Standard: Uncertified passive house
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AB OV E T H E C U RV E LIMERICK PASSIVE HOUSE SHOWCASES PRECISION TIMBER ENGINEERING
Sometimes it takes the constraints of a challenging site to bring out the best possible design, and that was certainly the case for this Limerick City passive house, where the project team managed to deliver a unique, curving passive house in response to a tricky urban plot. Words by John Cradden
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esigning a completely bespoke home on a tiny site in a very mature, built-up urban area is the kind of brief that many architects relish, not least the challenge of creating a distinctive form that functions brilliantly, while ensuring that it blends in aesthetically with neighbouring homes. Throw in the desire to build to the passive house standard, and you have quite the project. But spend a bit of time taking in the sight of this really interesting, three-bed, single-storey dwelling in Limerick city — particularly the way in which almost the whole house orients towards its curved courtyard — and you can very quickly see why architect Barbara Carr (of local practice Studiomove Architects) and her client, John , are so pleased with it. The new building has a bigger footprint than the original house that was demolished to make way for it, but it still blends in nicely. “The front of the house has very similar proportions to the bungalows that are there, and we didn’t want to do something that really jumped out,” Barbara says. “But inside it’s completely different. That’s why I called it the Tardis. When you come up, you can see that it’s different, but it really doesn’t shout out and I really loved that aspect of it. And then you come in the front door and there’s that sense of the sweep of the courtyard around the site that surprises you.” The Tardis certainly manages to maximise every one of the 220-odd square metres available to it, and while it butts up closely against neighbouring properties, being single storey means there is no risk of it overlooking adjacent homes. A driving force behind the project was John and his wife’s previous experience of living in an early 20th century red-brick home. Although they really loved the house, with its period features, it was registered with the local heritage council and they felt that any attempts to insulate it would be severely restricted. Even with a 30 kW condensing boiler and heating zones, the house struggled to keep them warm in winter. As an engineer, John had the idea of doing a self-build very firmly on his bucket list. He was in the fortunate position to be able to take some time off work to serve as the project manager and main contractor. When the opportunity arose to buy a house that came up for sale in the area, the couple decided to take the plunge, knocking down the original 1950s bungalow to create a clean slate for a new build. “Initially all I knew was I wanted to build a warm house. That was the starting point. So, I researched what could be done, what’s out there and it kind of led me on to the whole concept of the passive house standard,“ says John. “What I really liked about it, and this is from an engineering point of view... is that you could design and model the house up front and see how it would perform rather than coming up with a notional design and then hope it would work out.” He undertook the passive house designer training course run by MosArt Architects in Wicklow (which Barbara also did), and also decided to do a lot of the work himself, par-
The idea of wrapping the house around three sides of the site was adopted.
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Drone photos: Cathal Ryan / ARC Images
ticularly the mechanical and electrical, which allowed him to indulge in his enthusiasm for the latest in smart home automation technology from Loxone. While it’s clear from the performance figures that the Tardis works as a passive house, it was agreed early on that the design wouldn’t be a slave to the standard. “We didn’t want to wind up with a box, basically, with the windows on the south,” says John. So, while a warm, comfortable home was the main aim, achieving the standard – with or without certification — was a nice-to-have rather than a must-have. What made things tricky was the orientation. The original house faced south but straight onto a high, six metre high brick wall with an apartment block behind it. “We looked at it and thought ‘Oh, crikey’, Barbara says. “I mean, it’s a brilliant site in terms of its proximity to town and privacy, but the orientation then was really compromised by these things.” The idea of wrapping the house around three sides of the site was adopted so that the house orients towards the courtyard garden rather than the back wall. So, while it’s not far off the L-shape form that John had suggested, “it embraces the garden rather than addressing the wall,” says Barbara. “We calculated that we’d get enough south light into the courtyard of the house in summertime, but had to play around with window sizes as the curved courtyard crept around to face north. We also reduced the high-level north and east-facing windows in size.” Barbara says that because the form factor was not ideal for passive house — being single storey and spread out, there is a large surface area from which heat can escape — insulation and the orientation of windows was critical. A number of different build systems were investigated, including structural insulated panels, insulated concrete formwork (ICF) and blockwork, but it was decided that a twinwalled timber frame would give the best detailing and, more importantly, would lend itself to
the non-rectilinear shape of the house. Indeed, there’s no doubting that the geometry added a layer of complexity to the build, particularly with regards to the roof. Although it’s a mono-pitch, there’s a lot going on with it. It sweeps around in a curve, getting wider to accommodate high level windows above the kitchen and bathroom. All this, along with the curved courtyard window setting, generated a fair bit of “swearing” among the build team in its bid to make it all come together. Given the prominence and importance of the view facing out into the courtyard, the choice of external doors and windows was an important one. John and Barbara chose an Austrian company called Josko and even visited the factory, where they fell in love with their internal Venetian doors, made of bog oak. “These add a real wow factor to the interior,” Barbara says. “They are extra high, flush-fitting, in great finishes and with a magnetic latch system. There was quite a bit of work getting them to fit correctly.” It wasn’t in the plan, but they also opted to line the underside of zinc roof overhang in the courtyard with timber battens. It was felt that the view from inside out into the courtyard would look quite flat and dark with just the zinc roof overhang, and undermine the look of the beautiful timber windows. So, a joiner and his experienced father were commissioned to add matching battens, which they set using the radius of the curve of the building. “It took time to get them looking right,” Barbara says. “But now it’s really beautiful. It’s warm and you can see it from inside. So, you’re looking at your timber windows from inside, and then you look up and you see these battens as well. It’s one of those things that wasn’t decided before. I think we all love it.” On the foundation side of things, John liked the idea of an insulated raft foundation but the need to build up tight against the back wall effectively ruled that out, not to mention the – admittedly quite small – risk that an oil spill from the next door neighbour’s oil tank would
Anti-clockwise from top the curved courtyard-facing rear façade comes together, including curved steel frame; timber frame; airtight layer; and timber battens.
Main photos: Eamonn O’Mahony / Studioworks Photography
ph+ | timber engineering case study | 45
damage the EPS of the insulated foundation. A standard raft foundation was installed instead. The use of timber frame, supplied by Galway firm Long Life Structures, adds bonus points for a low carbon material, as does the cellulose insulation in the walls and roof. “The roof was what attracted me to the project really,” says Emmet Nee of Long Life Structures. “I always love doing curved work, curved carpentry. We’ve gained a bit of a reputation for doing challenging houses like this. “We see ourselves more as thermal envelope specialists rather than just timber frame suppliers. The good thing with timber frame is that the design stage of the drawings will show up any areas that require deep thinking, and that’s where you work it out. For this house we had to work out each individual roof rafter instead of doing one and repeating it 60 times.” The twin wall system used on this project, with two cellulose-filled studs separated by another layer of cellulose, is the company’s standard build method for passive house projects, as it eliminates thermal bridging through the walls. The company also boasts an enviable record of achieving better than 0.6 air changes per hour on every house it has built to date. “Airtightness doesn’t happen by accident, it has to be designed in,” Emmet says. “When we go to site we have our airtightness strategy honed in. The real challenge is when you’re erecting the frame — those are there areas you won’t be able to get to again. This is the reason we erect our own frames rather than sub-contract it out.” John and his partner moved in a year ago, so they’ve experienced both a summer and a
46 | passivehouseplus.co.uk | issue 38
The geometry added a layer of complexity to the build.
winter. “On the face of it, people think of passive houses as cheap to run and that’s it, but it’s actually a very, very comfortable house in terms of the constant temperature, with no drafts, and it’s a single zone temperature-wise throughout.” Since they had their smart meter installed by ESB networks, John has been tinkering around with the Nilan air-to-water heating and ventilation system to see how it works best in combination with the 3.5 kW solar PV panel array and a 4.8 kW battery. “Traditionally you might have your day and night meter, but now you’ll have maybe three or four different rates over the course of 24 hours and so we’re looking at how we can maximise that capability with a PV,” he says. As an engineer used to project-managing more complex industrial projects, John very much enjoyed managing this build on a personal level. “One of the things that I found with building this house is that there was emotion involved. If you’re doing an industrial project, you have a specification, you’re not worried about colours or worried about would the client be happy with this or that and so on.” “When people look at these Grand Design programmes and so on, they have no idea what’s going to happen in the background in terms of the complexity involved in it. The best thing I ever did was to do the passive designer course, to bring myself up to speed, you know, from selecting windows, to detailing, to minimising thermal bridges and so on. I’ve learned so much from it, it’s absolutely unreal.” No doubt he enjoyed installing the state-ofthe-art smart home system that controls everything from lighting to blinds to heating. “He had great fun with that,” Barbara says. Personal joys aside, John is also clear on what the project has achieved and is actively considering applying for passive house certification. “We pushed the envelope in terms of getting as close as you can to the passive standard without sacrificing aesthetics in an urban, built-up area.”
ph+ | timber engineering case study | 47
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48 | passivehouseplus.co.uk | issue 38
CONSTRUCTION IN PROGRESS
1 & 2 Installation of the curved courtyard windows, triple glazed aluclad units from Josko; 3 timber cladding was fitted to the underside of the zinc roof overhang in the courtyard for aesthetic reasons; 4 Intello vapour control membrane and airtightness taping to ceiling; 5 the Nilan Compact P combines heat recovery ventilation along with air heating and cooling; 6 solar battery and Solis Hybrid inverter.
SELECTED PROJECT DETAILS Architect: Studiomove Architects Civil & structural engineering: Mike Boyce Consulting M&E design: GEON Timber frame & raft foundation: Long Life Structures Quantity surveyor: Steadfast Mechanical contractor: Paul Corcoran Plumbing & Heating Electrical contractor: Deegan Contracts Limited Airtightness test: Hession Energy Cellulose insulation: Darmstadt, via Clíoma House Wufi analysis: Ecological Building Systems Airtightness products: Clíoma House Windows & doors: Josko, via DG Windows & Doors Space heating & ventilation: Nilan Ireland Roof windows: Fakro Blinds: Shade Tec Cladding: Aquapanel, via Greenspan Roofing: A & A Quinn Roofing Polished concrete floor: Mapei, via Topcoat Systems Landscape design: Manila Landscape Design Home automation (Luxone): GEON Lighting design: Wink
WANT TO KNOW MORE? The digital version of this magazine includes access to exclusive galleries of architectural drawings. The digital magazine is available to subscribers on passivehouseplus.ie & passivehouseplus.co.uk
ith a cradle to grave score of 483 kg CO2e/m2 GIA, this project beat the RIBA 2030 Climate Challenge target of 625 kg CO2e/m2 GIA, according to calculations by John Butler Sustainable Building Consultancy using PHribbon. While the revised RIBA methodology is aligned with LETI’s embodied carbon targets, it differs in a crucial regard: LETI excludes embodied carbon emissions from PV arrays, considering them as part of the electricity grid, effectively. Excluding the large PV array in this case would cause the figures to drop by a further 37 kg CO2/m2. The calculations included a number of assumptions where necessary, in particular in the area of mechanical, electrical and plumbing services, where environmental product declarations (EPDs) remain rare. Data from a French Product Environmental Passport for the heat pump which most closely resembled the compact unit installed was used, and data for stainless steel ductwork was used in the absence of polypropylene ductwork data. The analysis included interior and exterior finishes, sanitaryware and sinks, but not all fitted furniture, fixings and equipment. Default or comparable data was used in a number of other areas. Transport emissions were adjusted to provide rough approximations for given product types. No replacements were assumed for the fabric, and two replacements of the heat pump were assumed – albeit with inert refrigerants assumed – within the 60 year projected lifespan in the calculations. A comparison between the as built external wall system and a notional cavity wall build up to the same specifications –
with transport and construction emissions adjusted accordingly for those elements specifically – showed cradle to practical completion figures of 58 kg CO2e/m2 for the as built walls (including 30 kg CO2e/m2 for materials) versus 114 kg CO2e/m2 for the cavity wall comparison (including 93 kg CO2e/m2 for materials). The complete building as built was compared to the same complete building built with cavity wall construction and with no GGBS substitution in the foundations. The cradle-to-grave figures increased from 483 to 563 kg CO2e/m2, while the as-built spec also included 150 kg CO2e of sequestered CO2 in the timber and timber-based products, whereas the alternative with cavity walls was estimated to include 83 kg of sequestered CO2e (both versions assumed the same timber and timber-based products used for internal walls and roof build up). As ever, it is worth remembering that the module C emissions relate to the end of life at the building. The majority of the module C emissions relate to sequestered CO2 in the timber and timber-based products, and it is assumed that these emissions are released at the building’s end of life – with 75 per cent of timber assumed to be incinerated, and 25 per cent landfilled. Even if the timber was instead assumed to be recycled or reused, the sequestered emissions would move outside of the boundary conditions of the building life cycle assessment, and pass on to the next use. While this may give the appearance that a significant amount of CO2 is released into the atmosphere at the building’s end of life, it is possible that timber may remain sequestered in buildings for hundreds of years.
ph+ | timber engineering case study | 49
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www.munsterjoinery.co.uk WINDOWS & DOORS 50 | passivehouseplus.co.uk | issue 38
IN DETAIL Building type: Detached 223 m2 timber frame house. Location: Limerick City
or €25 per month inclusive of VAT, but excluding standing charge and PSO levy. These figures are based on final energy demand (delivered energy) figures from the PER sheet of PHPP.
Completion date: February 2020
timber I-beam rafter (at various centres due to radius of roof) filled with Darmstadt Thermofloc cellulose insulation, Intello Plus vapour control membrane, 50 x 50 mm battens at 400 mm c/c to form service cavity, 12.5 mm Gypsum plasterboard and skim. U-value: 0.116 W/m2K
Airtightness: 0.5 ACH at 50 Pascals Budget: Not disclosed Passive house certification: Uncertified Space heating demand: 18.44 kWh/m2/yr (PHPP) Heat load: 9.73 W/m2 (PHPP) Primary energy non-renewable: 65 kWh/m2/yr Heat loss form factor: 4.0 Overheating: 10% (PHPP) Number of occupants: 3 Energy performance coefficient (EPC): Pending Carbon performance coefficient (CPC): Pending BER: Not yet completed Environmental assessment method: N/A Measured energy consumption & energy bills: During 2020, the household electricity bill averaged €80 per month, for all space heating, hot water & electricity. However, John installed a solar PV array in September 2020, and a smart meter with varied electricity rates in April 2021. This already appears to be making a big difference in electricity consumption. For example, while the house consumed 1,645 kWh in May 2020, its projected energy consumption for May 2021 was just 370 kWh (as of May 25). For space heating & cooling only, taking the current Energia day rate (0.1565c), this property would have an estimated bill for space heating and cooling of €300 annually
Thermal bridging: Walls, pitched and flat roofs all in timber frame with cellulose insulation meant that the line of insulation was continuous from one plane to another. A twin wall timber frame system, 330 mm thick overall, helped to reduce thermal bridging. Psi values were taken as default 0.08 W/ mK, apart from the curved courtyard wall. The detail around a steel beam above the large window/door wall to the courtyard had a calculated psi value of 0.04 W/mK. Foundation/wall psi value was 0.01 W/mK. Ground floor: 150 mm thick reinforced concrete slab (grade C30/37) followed above by 280 mm Mannok Therm Floor PIR insulation, with ducting pipework for Nilan ventilation cut in, 75 mm screed containing pipework for underfloor heating. 12 mm grey Mapei Ultratop Terrazzo & Irish beech pebble polished concrete finish. U-value: 0.078 W/m2K Walls: 20 mm Aquapanel exterior cement board, followed inside by 50 x 50 mm timber battens to create ventilated cavity, 22 mm timber sheeting and pro clima Solitex Humida Fronta Quattro wind-tight membrane, 89 x 38 mm outer leaf non-loadbearing stud at 600 c/c filled with Darmstadt Thermofloc cellulose insulation (0.037 W/mK), 100 mm layer of cellulose between inner and outer timber frame, 140 x 38 mm inner load bearing stud at 600 c/c filled with cellulose insulation, 12 mm Durelis Naturespan Vaporblock racking airtightness layer, 50 x 50 mm battens at 400 mm c/c to form service cavity, 12.5 mm Gypsum plasterboard and skim. U-value: 0.120 W/m2K Roof: Zinc cladding with standing seams, followed inside by Alutrix vapour barrier, 18 mm penny gap boarding, 50 x 50 mm timber battens, 18 mm OSB sheeting, 300 mm deep
Roof, flat: Fatra PVC membrane, followed beneath by 120 mm TR 26 PIR insulation board, vapour barrier, 18 mm plywood sheeting, timber firring pieces falling from 92 to 50 mm (1 in 80 fall), joists 170 x 44 mm with full fill cellulose insulation, Intello Plus vapour control membrane, 100 x 38 mm battens at 400 mm c/c to form service cavity, 15 mm gypsum plasterboard and skim. U-value: 0.105 W/m2K Windows: Josko Platin Plus triple glazed aluclad timber windows. U-value: 0.82 W/m2K average for the project. Roof windows: 2 x Fakro U8 triple glazed roof windows. U-value: 0.8 W/m2K Heating system & Ventilation: Nilan Compact P XL (430 m3/hr) unit which combines heat recovery ventilation along with air heating and summer air cooling through the balanced ventilation ductwork. Passive House Institute certified. Effective heat recovery efficiency: 80% (PHi), calculated with PHPP, considering stated efficiency and installation. The Compact P is backed up with a Nilan air-to-water heat pump (Air9) which provides weather compensated hot water to zoned underfloor heating circuits. Seasonal coefficient of performance for Compact P and Air9 (variable speed compressor output power) Ecodesign A+++ SCOP 511% efficiency. Water: N/A Electricity: 19 m2 Trina Mono solar photovoltaic array with 3.48 kWh installed capacity. Battery storage 4.8 kWh. Solis Hybrid inverter. Green materials: Cellulose insulation, timber frame.
ph+ | timber engineering case study | 51
PER MONTH FOR SPACE HEATING ONLY (Estimated, see ‘In detail’ for more)
Building: 206 m2 deep retrofit & extension to detached dwelling Method: External insulation & timber frame extension Location: Ballisodare, Co Sligo, Ireland Standard: Fabric first retrofit Energy rating: A3
52 | passivehouseplus.co.uk | issue 38
EFFECT SLIGO DEEP RETROFIT DELIVERS WARMTH, LIGHT AND SWEEPING MOUNTAIN VIEWS
Complete with butterfly roofed extension, this fabricfirst renovation has turned a cold and uninspiring 1970s bungalow into a cosy A-rated modern home, with some clever design touches helping to open the house up to wide-angle views and dramatic coastal light. Words by John Hearne
ph+ | west ireland case study | 53
erek Sherlock bought the bungalow which would eventually become his and his wife’s new home back in 2014 and rented it out while researching how he might renovate it. At the time, he says, it was probably the coldest house he was ever in. “Drafts? Lot of drafts coming up through floorboards. It had an uninsulated suspended timber floor. We rented it to a builder’s son, and he went around the skirting board with some sort of a tape to try to cut down on the drafts. They had a double layer of curtains in the TV room just to try to keep the heat in. It was one cold bungalow.” Their family reared, Derek and his wife had decided to downsize, and return to his homeplace in Ballisodare, County Sligo. The house they bought was your typical 1970s bungalow: long and dark, with an uninspiring layout, and, as he was quick to find out, an even more uninspiring thermal profile. There had been attempts to upgrade the insulation and the windows over the years, as well as an ill-advised attic conversion that fell far short of acceptable space and height standards. The house really had only one good feature: there are stunning views of Knocknarea and Benbulbin to the north and the Ox Mountains to the south. Taking advantage of those views would be a key element of the renovation. So too would comfort.
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“I wanted it to be good for the environment, but I also wanted it to be really comfortable for myself and my wife,” says Sherlock. “The money thing wasn’t a big motivator, though it’s actually cheaper to run than I thought it would be.” More about that later. Light was another key requirement, as was a more modern layout and additional downstairs space. In the two years prior to the start of the project, Derek and his wife did the rounds of building expos in Dublin and Belfast, talked to a lot of experts, and explored the full range of options that were open to them. “I looked at windows – would we do double or triple glazing? External wall insulation? Would we dryline it? Pump the walls? Were we going to do underfloor heating or rads? We looked at solar panels, heat pumps, oil or gas. Everything.” Derek also read Passive House Plus eagerly during this time to glean ideas for the project, and to learn about low energy building. He bought himself a maths copy, in which he sketched out the existing layout of the house, then began experimenting with different layouts and extensions, looking for ways to introduce light and create better room configurations. He also engaged James Walsh of Low Energy Design to assist with this element of the project. Walsh is a passive house architect with exten-
I wanted it to be good for the environment, but I also wanted it to be really comfortable.
The butterfly roof allowed us to bring in morning light.
Photos: Kelvin Gillmor
sive experience. His work on St. Bricin’s Park, a Dublin City Council passive refurbishment project in Arbour Hill, was profiled in issue 30 of Passive House Plus. Working together, they created a design which sought to make the most of the spectacular views, ensure a light-filled living space and deliver the levels of thermal comfort that had been so absent in the original design. “We designed an open plan for the kitchen, dining and living area,” Walsh explains. “It’s L-shaped so that you can see Knocknarea out through the corner window. We also built a butterfly roof because the house is north-facing at the back, which is the elevation where you get those spectacular views. The butterfly roof allowed us to bring in morning light through high level windows on the east, and evening light though high level windows on the west.” He points out that a standard A-type roof would have made it difficult to get sufficient light into the space, and that the butterfly roof had the added advantage of creating a more interesting profile. In the same vein, Sherlock wanted something more than a simple rectangular extension out the back. “I wanted to make it a bit interesting from the road. That’s why we put on the red cedar cube. We could have gone straight out into the back garden and put nothing on the gable, but that would have left us with one big rectangle. Instead, we went a certain distance out into the garden, then added that cube. My vision was that that was going to be our sitting area in the evening. I just didn’t want to be sitting in a corner of a big square box. I wanted to put a bit of a twist on it.” With so little to be salvaged from the original house, the build team removed the roof and broke the structure back to the walls. The existing raised timber floor was also removed, allowing the installation of a new, well-insulated floor, together with an underfloor heating system. When contractor Dermot Dunne exam-
ined the walls, he discovered that they were not entirely insulation free. At some point in the building’s history, someone had pumped in insulation. Unfortunately however, it turned out to be some form of formaldehyde. “I couldn’t put a definite date on it,” says Walsh. “I’d read reports of issues to do with toxicity and off-gassing with this type of insulation. This probably would not be an issue because it had very likely been in place for more than five years. The other problem however was that it had shrunk in places, and I didn’t want to run the risk of leaving voids in the cavity. We got a specialist company in to suction it out, we cleaned it and then got it re-pumped.” In order to bring wall U-values up to spec, and to help eliminate cold bridges, external wall insulation was also added. Contractor Dermot Dunne had not installed external insulation before, but he registered with the SEAI as an installer and took guidance from the supplier before installing 150 mm of Baumit Graphite EPS. Thermal bridging is often a headache in retrofits. Here, in addition to the external insulation, the build team deployed thermal blocks at key junctions in new external walls, ensured insulation ran below the level of the perimeter path outside the house, designed the eaves for thermal continuity, and ensured the windows sat within the insulation zone. Sherlock was also keen to have underfloor heating throughout the house, so the engineer specified a very dense grade of timber for the flooring (dense timber conducts heat better) and installed a screed in the first floor too. Installing ventilation ducting in restricted spaces was another challenge on the build, as of course was airtightness. In meeting all these challenges, James Walsh talks about the crucial importance of getting sequencing right at the planning stages in order to ensure that insulation and airtightness measures are not adversely impacted after they have been fitted.
ph+ | west ireland case study | 55
CONSTRUCTION IN PROGRESS
1 The existing 1970s bungalow prior to retrofitting; 2 the house suffered from mould problems; and 3 had urea-based insulation in the cavity; 4 the old roof removed and the house stripped back to the structure; 5 installation of new triple glazed windows; 6 gap left under the eaves for external wall insulation, which would meet the roof insulation; 7 & 8 Mannok thermal blocks, which are lighter in colour, were deployed at key junctions to prevent thermal bridging; 9 construction of the new roof underway; 10 SIGA Majpell airtightness membrane and taping; 11 SIGA Majcoat wind-tight breathable membrane to the roof; 12 underfloor heating was installed on both floors.
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“It wasn’t the case on this house, but I’ve done a number of jobs where, for example, you’re putting insulation in the ceiling, and afterwards, the plumber realises that an additional pipe has to go in. They might lift the insulation and then fail to put it back properly. Those kinds of things do happen,” he says. Getting everyone on site conversant with insulation and airtightness targets is another great way of ensuring that no one does anything to compromise them. On the aforementioned St Bricin’s passive retrofit scheme, Walsh says the success of that project owed a lot to the fact that onsite training was provided for all of the tradespeople involved.
On this project, it is interesting to note that the best views and the extensive glazing lie to the north of the house. “Before we started,” says Derek Sherlock, “I used to think, ‘God, if those views were on the other side of the house, we’d have all of this lovely sun in the living room’ but I realise now that we just couldn’t have lived with that... the glare would have meant that you would have had to have blinds on the windows and would have had no comfort sitting there.” He also thinks that unimpeded glazing on the south elevation would have caused overheating. James Walsh says that there was no major thermal loss a result of having these glazed sec-
They had a double layer of curtains just to keep the heat in.
ph+ | west ireland case study | 57
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tions to the north. “The north facing glazing was a deliberate design decision,” he says, “to take advantage of the magnificent views and slightly elevated site. As Derek was amenable to using triple glazed windows and doors with U-values of 0.8 generally, I knew that they would contribute to the thermal performance. That was reflected in the overall DEAP assessment and building energy rating. The wall U-values are predominantly 0.15 with some small sections at 0.13 and 0.17.” The house also gets quite close to Ireland’s nearly zero energy building standard (NZEB) for new build, beating the NZEB carbon performance coefficient target of 0.35 but narrowly missing out on the energy performance coefficient target of 0.3 (the house scored 0.34). When it comes to costs, Sherlock confirms that he has been pleasantly surprised. “From June 2017, when we moved in, to June 2018, the total cost of all electricity – not just the heat pump – came to €1,120. Then from June 2018 to June 2019, it went up by €40 to €1,160. And the following year, it was up a little further, to €1,200.” He notes too that he “never touches” the Ecodan air-to-water heat pump. The thermostat has remained set to 21 C since he and his wife moved in. The increase in bills over the last two year he attributes to rising energy prices as opposed to increased energy use. “It’s fabulous,” he says, “just fabulous. We love it here.”
SELECTED PROJECT DETAILS Client: Derek Sherlock Architect: Low Energy Design Main contractor: Dunwall Construction Civil & structural engineer: David O’Hara BER assessor: Energy Rating (Sean Clancy) Mechanical contractor: Tommy Finn Electrical & Plumbing Electrical contractor: Paul Morahan Electrical Services Airtightness tester: Ecoscan External wall insulation: Baumit, via Chadwicks Cavity wall insulation: Abbey Insulation Thermal blocks: Mannok Roof insulation: Isover Additional roof insulation: Mannok Airtightness products: SIGA Windows & doors: Munster Joinery Roof windows: Velux Roofing: Tegral Heat pump: Mitsubishi Ecodan, via Tommy Finn Electrical & Plumbing MVHR: Beam Vacuum & Ventilation MVHR installation: Paul Morahan Electrical Services
WANT TO KNOW MORE? The digital version of this magazine includes access to exclusive galleries of architectural drawings. The digital magazine is available to subscribers on passivehouseplus.ie & passivehouseplus.co.uk
ph+ | west ireland case study | 59
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| issue 38
IN DETAIL Building type: Deep retrofit & extension of detached 148 m2 1970s bungalow into 206 m2 dwelling. Location: Abbeytown, Ballisodare, Co Sligo Budget: Private Completion date: June 2017 BER Before: G (539 kWh/m2/yr) After: A3 BER (51.6 kWh/m2/yr) Energy performance coefficient (EPC): 0.336 Carbon performance coefficient (CPC): 0.317 Space heating demand (primary energy, DEAP): 11 kWh/m2/yr Energy bills: The client reports an average annual electricity bill (covering all energy use in the house) of €1,150, or €95 per month. The DEAP assessment of the house projected a delivered energy demand for space heating of 1,085 kWh/yr or 5 kWh/m2/yr. According to the cheapest available tariff available from Bonkers.ie, this would cost €203 including VAT at 13.5 per cent, or approximately €17 per month. This does not include standing charges or the PSO levy. Number of occupants: 2
insulation, new radon membrane and sump. U-value: 0.12 W/m2K Walls Before: Concrete block cavity walls with blown 60 mm cavity (insulated with formaldehyde). U-value: 1.78 W/m2K After: Silicone render finish externally on 150 mm Baumit Graphite EPS (0.031 W/mK) external wall insulation, on existing external cavity block leaf, removed formaldehyde insulation from cavity and cleaned cavities, pumped cavity with 60 mm platinum bead insulation, inner blockwork and internal plaster. U-value: 0.15 W/m2K Roof Before: Roof slates to sloped areas, room in roof with mineral wool insulation between rafters and studs. Pitch roof ceiling areas with 100 mm mineral wool insulation on the flat between roof joists. Plasterboard ceiling internally. U-value: 2.3 W/m2K After: Tegral fibre cement slates externally on 50 x 35 battens/counter battens, followed underneath by SIGA Majcoat wind-tight breathable membrane, 225 mm timber I-joists fully filled with Isover Metac insulation (0.034 W/mK), SIGA Majpell airtight & vapour control membrane, 75 mm insulated service zone with Isover Metac, 12.5 mm plasterboard ceiling. U-value: 0.16 W/m2K
Mannok Therm MFR-FFR PIR (0.022 W/mK), on 150 x 44 C16 roof timbers at 400 centres fixed to structural steel in accordance with engineer’s specification, on SIGA Majpell airtightness membrane, 75 x 50 battens at 600 centres for service zone and 12.5 mm plasterboard with skim finish internally. U-value: 0.16 W/m2K Side Extension roof: Single ply membrane followed underneath by 140 mm Mannok Therm MFR-FFR PIR (0.022 W/mK), on 150 x 44 C16 roof timbers at 400 centres fixed to structural steel in accordance with engineer’s specification, on SIGA Majpell airtightness membrane, on 75 x 50 battens at 600 centres for service zone and 12.5 mm plasterboard with skim finish internally. U-value: 0.15 W/m2K Windows & doors Before: Single glazed and some double glazed, timber / pvc windows and doors. U-values range: 2.4 - 4.8 W/m2K After: Munster Joinery triple glazed, argon filled, Passiv uPVC windows and doors: Overall average U-value of 0.80 W/m2K. Roof windows: Velux triple glazed roof windows. Overall U-value: 1.0 W/m2K Heating system Before: 20 year old oil boiler & radiators throughout entire building, with peat open fires.
Measured energy consumption: N/A Heat loss form factor: 2.7 Airtightness (at 50 Pascals): 1.94 air changes per hour (1.88 m3/hr/m2) Ground floor Before: Uninsulated suspended timber floor. U-value: 0.65 W/m2K After (upgraded): new concrete floor with 150 mm Mannok Therm Floor insulation (thermal conductivity 0.022 W/mK), 75 mm screed with underfloor heating & 40 mm perimeter
Extension walls 1: Silicone render finish with 250 mm Graphite EPS (Conductivity 0.031 W/ mK), on 215 mm blockwork with internal plaster: U-value: 0.13 W/m2K Extension walls 2: Cedar timber cladding externally on treated battens, on breather membrane over 350 mm cavity block wall with 150 mm blown bead insulation (0.031 W/mK) to cavity, internal plaster finish. U-value: 0.17 W/m2K Extension butterfly roof: Single ply membrane externally, followed underneath by 140 mm
After: Mitsubishi EcoDan Monobloc air-to-water heat pump serving underfloor heating (on both floors) and towel rails. 508 per cent efficiency for space heating and 226 per cent efficiency for water heating. Ventilation Before: No ventilation system. Reliant on infiltration, chimney and opening of windows for air changes. After: Beam Axco C90 mechanical ventilation heat recovery ventilation system — heat recovery efficiency of 85 per cent.
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S IX OF ON E AN ANALYSIS OF THE EMBODIED CARBON FROM SIX WAYS OF BUILDING A HOUSE
The climate emergency demands that we minimise the energy we use to operate buildings, as well as the energy we use to construct new buildings, where new buildings are needed. A Passive House Association of Ireland-commissioned analysis may start to shed some light on the embodied carbon impact that different build methods can have. Words by Jeff Colley
he embodied carbon of walls and foundations on new homes can be cut by 50 per cent or more, an analysis commissioned by Passive House Association of Ireland (PHAI) has revealed. The PHAI commissioned the Association for Environment Conscious Building (AECB) to conduct the analysis using PHribbon, a tool which enables embodied carbon to be calculated via the PHPP passive house design software. The AECB calculated the cradle-to-grave embodied carbon emissions of a 76 m2 end of terrace house provided by Cork City Council. The building was modelled in Sketchup by AECB chief executive Andy Simmonds, with the calculations carried out by PHribbon creator Tim Martel, working in collaboration with the author, and fellow PHAI board member John Morehead.
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The house was designed to meet compliance with Ireland’s nearly zero energy building (NZEB) standard, including the following energy performance specifications: U-values W/m2K Walls: 0.145 – 1.64 Roof: 0.105 – 0.134 Floor: 0.101 – 0.137 Windows: 1.15 Doors: 1.1 Y-factor: 0.06 Mechanical extract ventilation Airtightness: 3 m3/hr/m2 at 50 Pa. Heating system: 6 kW air-to-water heat pump
Wain Morehead Architects prepared DEAP calculations to demonstrate that the specification complied with Ireland’s NZEB requirement for dwellings. Building LCA modules: a brief explanation With embodied carbon assessment generally there are certain areas where it’s possible to reach relatively clear conclusions with high degrees of confidence, while other aspects of the calculation may be more speculative. Life cycle assessment is divided into four modules: A, B, C and D. Module A deals with the building construction up to the point of practical completion. This is the area where there is most scope for accurate embodied carbon calculation, for the simple reason that it involves assessing the impact of works that have been done.
BASE CASE 1A
Walls 12.5 mm plaster 100 mm blockwork 140 mm PIR 100 mm blockwork 19 mm 1:4 cement: sand render Floor 20 mm engineered timber floor 75 mm cementitious screed 150 mm PIR 225 mm concrete + strip foundation 150 mm aggregate A1-A3 (materials only, cradle to factory gate): 18.8t CO2e A1-A5 (cradle to practical completion): 25.2t CO2e A-C (cradle to grave): 25.2t CO2e Stored CO2: -1.1t CO2e
Module B deals with the use phase, including maintenance, repair, replacement and refurbishment. (It can also include operational energy use, but this is reported separately in the RIBA 2030 Climate Challenge, and in this analysis). It therefore involves making predictions about how the building will be operated, and about how long certain components may last. This can be affected by the quality of component, or by the quality of the design and construction, and also by occupant behaviour. For instance, if a building design hasn’t adequately considered surface or interstitial condensation risk, this may result in mould growth and potential for
redecorating, repair to building fabric and in catastrophic cases, reducing the lifespan of the building. This can be exacerbated with occupant behaviour – especially where occupants are underheating or under ventilating buildings, hanging clothes indoors to dry, or placing furniture against external walls. Module C deals with the end of life of the building. In line with the RICS methodology, this analysis assumes a 60 year lifespan. In reality, it is to be hoped that the lifespan is far longer. The historic replacement rate of housing stock in the UK is 0.5 per cent per annum, indicating that a 200 year lifespan should be possible for the main elements of a building. At the building’s assumed end of life, CO2 emissions associated with deconstruction/demolition are added. Emissions locked up in timber and timber-based products are assumed to be released at this point. The default assumption is that 75 per cent of timber is incinerated, and therefore the CO2 is released, with 25 per cent being landfilled, and breaking down as methane, which has a considerably higher global warming potential than CO2, and actually increases the CO2 equivalent (CO2e) figure more than incineration would. Even if it’s assumed that the timber is in fact reused or recycled instead, the sequestered CO2 moves outside of the boundary conditions of the life cycle assessment. The benefit passes on to the next use – meaning the LCA effectively regards it as being released into the atmosphere anyway. Module D deals with the potential for reuse, recovery and recycling, beyond the boundaries of the LCA. These figures can’t be included in the cradle to grave figures, so we’ve elected not to include them in this analysis. A particular focus on Module A is illustrative. A1 to A3 relates to the upfront emissions in manufacturing the materials – everything emitted up to the factory gate. A4 relates to transporting those materials from the factory gate to the site, and A5 relates to the construction process itself. The data available presently tends to be clearest with regard to module A1-A3, as a growing number of manufacturers have already obtained Environmental Product Declarations (EPDs) or a French equivalent, the Product Environmental Passport (PEP), both of which include independently audited embodied carbon values for given products. There are also generic EPDs organised by industry bodies, which are intended to provide typical results for a given product type. These are less accurate than EPDs for specific products, for the very obvious reason that they don’t relate to a specific product. The vast bulk of EPDs tend to exist for building fabric products. Manufacturers of mechanical, electrical and plumbing products have tended to be less likely to obtain EPDs, though some relevant data is now available via the PEP database (www.pep-ecopassport.org). This analysis focuses on the materials in the building fabric: the substructure (including insulation, cement-based screed and hardwood flooring), the external walls, windows and doors, internal walls and intermediate
floors, the roof, and internal finishes to a builder’s finish. The heat pump is included, but there is no allowance for plumbing and heating distribution systems, electrics and lighting, the ventilation system, sanitaryware, bathroom and kitchen fitout, staircase, or for furniture, fixtures and equipment generally. Similarly, with the fabric, some information has been omitted in certain cases: such as wind posts and cavity closers. We have elected not to name proprietary products in general, although where possible, values were taken from actual EPDs for proprietary products. It is relatively tricky to obtain accurate data
BASE CASE 1B
Walls 12.5 mm plaster 100 mm blockwork 140 mm PIR 40 mm air gap 102.5 mm brick Floor 20 mm engineered timber floor 75 mm cementitious screed 150 mm PIR 225 mm concrete + strip foundation 150 mm aggregate A1-A3 (materials only, cradle to factory gate): 20.7t CO2e A1-A5 (cradle to practical completion): 27.3t CO2e A-C (cradle to grave): 27.7t CO2e Stored CO2: -1.1t CO2e
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undertaking for this analysis. For instance, take the case of concrete foundations. While there are concrete product manufacturers relatively local to the site of the project in this analysis, not all of the ingredients would have been sourced at or near the factory. Also, while return journeys may not be an issue with national or international travel – in many cases articulated lorries delivering materials to a local depot would be taking other goods on return journeys – this is much less likely with smaller rigid lorries, meaning a 50 km local freight assumption may be an underestimate. In line with the RICS methodology, the default data for emissions related to the construction process (A5) is based on the economic value of the project. The analysis includes certain elements which remained common in all cases: the roof and ceiling build up, internal walls and intermediate floor, windows, concrete sills and lintel, and heat pump. The only areas where variations were assessed included the external walls and the ground floor spec, including foundations. A health warning is necessary on the concrete figures. Data for the foundations in the base case was sourced from an EPD for a CEM
wall insulation (EWI) and a silicone-based render system. Upgrade 2A and 2B include EWI with render and brick slips respectively, and in both cases substitute the strip foundation for an insulated raft foundation system, including 50 per cent substitution of ordinary Portland cement (OPC) with GGBS. Upgrade 3 retains the same insulated foundations spec, but switches to a cellulose-insulated timber frame wall, finished with a rendered cement board system. Material impacts: walls and floors It is worth first considering the embodied carbon emissions of materials by the time they leave the factory gate, given that it’s possible to pin down these figures with greater certainty, and to focus first on the areas where variations were considered: external walls and foundations. The worst performing option in this case is Base Case 1B, the brick-clad cavity wall build, which comes in at 20.1 tonnes of carbon dioxide equivalent (CO2e), a measurement used to compare emissions of all greenhouse gases based on how their warming impact relates to that of carbon dioxide. Simply switching from brick to a rendered block outer leaf (Base Case 1A) drops the
The best performing option is Upgrade 3, the timber frame build on insulated foundations, which comes in at 9 tonnes of CO2e. Walls 12.5 mm plaster 215 mm blockwork 8 mm scratch coat 200 mm EPS 6 mm proprietary silicone render 450 x 150 mm PUR Aircrete block course in foundation wall Floor 20 mm engineered timber floor 75 mm cementitious screed 150 mm PIR 225 mm concrete + strip foundation 150 mm aggregate A1-A3 (materials only, cradle to factory gate): 17.2t CO2e A1-A5 (cradle to practical completion): 23.6t CO2e A-C (cradle to grave): 24.9t CO2e Stored CO2: -1.1t CO2e
on transport to site (A4). PHribbon includes default assumptions on transport based on UK government data on freight emissions, with different estimates per tonne km for sea freight, national road freight and local road freight. Based on the RICS methodology, PHribbon includes default transport distances of 300 km for national freight on an articulated lorry, and 50 km local freight on a smaller rigid lorry. In some instances, estimates have been made based on likely actual distances, but in practical terms this was often too much of an
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I-based concrete – where 95 per cent or more of the cement is clinker (the active ingredient in cement). A lower embodied footprint would have been achieved by using CEM II – which has become the default product for most concrete applications in Ireland, excluding precast concrete. However, CEM II cement has a broad bandwidth – comprising from 65 per cent up to 95 per cent cement clinker, with different options for additions such as GGBS, fly ash or limestone – meaning it’s unclear how much of a reduction compared to CEM I that CEM II will achieve, unless the cement manufacturer has declared the amount and type of additives used in the CEM II cement. The figures for concrete blocks are derived from an industry association EPD, which doesn’t specify the type of cement used – meaning it’s not possible to reach conclusions on its constitution. The analysis established two base cases, Base Case 1A and 1B, derived from what was considered to be a typical Irish reference: a cavity wall building with strip foundations, with both the floor and cavities insulated with oil-based insulation board. The only difference between the two was the outer leaf: rendered blockwork in the case of Base Case 1A, and a brick outer leaf for Base Case 1B. Upgrade 1 includes one change: instead of cavity walls, it includes a single leaf 215 mm block-on-flat fitted with oil-based external
total to 18.2 tonnes. Switching to single leaf 215 mm blockwork with rendered external insulation as per Upgrade 1 drops the total to 15.4 tonnes. A further significant drop to 11.4 tonnes is achieved in Upgrade 2A by switching from conventional foundations to an insulated foundation system with 50 per cent GGBS. Upgrade 2B sees the total rise again to 13.8 tonnes, due to switching from a rendered finish to brick slips. The best performing option is Upgrade 3, the timber frame build on insulated foundations, which comes in at 9 tonnes of CO2e. Sequestered CO2 It’s important to treat the sequestered CO2 figures with care. After all, timber-based construction products don’t suck CO2 out of the air – forests do. The notion of achieving carbon negativity by using vast quantities of timber may be too simplistic. But notwithstanding issues around the need for broader attention to sustainability in forestry management, a strong environmental case can be made for lean timber-based approaches, such as those that make structural use of Larsen trusses or I-beams. Upgrade 3 in this analysis therefore opted for just such an approach. In terms of the wall and floor analysis, the sequestered CO2 in the timber and timber-based products used, including cellulose insulation – is
almost equivalent to the entire A1-A3 emissions for the wall and floor. However, this is not to suggest that one figure should be netted off against the other. While there is a value in keeping CO2 sequestered in buildings – hopefully for centuries – perhaps the more significant point is that by stage A1-A3, the timber frame and insulated foundation option in this analysis had emitted less than 40 per cent of the emissions of the brick-clad base case. This is not down to the timber frame alone, but to the application of a combination of
Walls 12.5 mm plaster 215 mm blockwork 8 mm scratch coat 200 mm EPS 6 mm proprietary silicone render 450 x 150 mm PUR Thermal (AAC) block course in foundation wall Floor 75 mm screed 200 mm concrete (50% GGBS) 250 mm EPS150 A1-A3 (materials only, cradle to factory gate): 11.4t CO2e A1-A5 (cradle to practical completion): 16.6t CO2e A-C (cradle to grave): 18.5t CO2e Stored CO2: -1.1t CO2e
carbon saving yet mainstream materials: cellulose insulation, GGBS, cement board, silicone render and a foundation approach that reduces the amount of concrete used. There is also some sequestration assumed via carbonation of concrete in the case of
Transport and construction emissions When transport and construction emissions are considered, the differences between the different build approaches look a little less pronounced, because construction emissions – estimated based on the value of the project, which is assumed not to have changed – are identical in each scenario, at 1.2 tonnes for the walls and ground floor. As mentioned before, the transport data is much less precise than the materials data, given the use of default values in this case. Interestingly, in spite of the fact that many of the materials in the timber frame option are estimated to have travelled far greater distances – such as the cement board, wood fibre sheathing and silicone render – its transport emissions total remains far lower than the base cases – 3.2 tonnes compared to 5.9 tonnes for Base Case 1A and 6.2 tonnes for Base Case 1B. This is for a few reasons: the carbon factors for rigid HGVs assumed locally are far higher than large artics assumed for larger distances, sea freight emissions are very low in relative terms, and heavy materials add considerably to the transport emissions. Use stage In the use stage (Module B), the analysis generally assumed that the building fabric measures would last for the 60 year lifespan of the building set out in the RICS methodology. This rationale is supported by the existence of 60 year design life statements in Agrément certificates for proprietary systems in the case of cement fibre boards and external insulation systems. In the case of the building’s double glazed windows, a 40 year lifespan has been assumed, meaning one replacement is included in module B. Base Case 1A was assumed to have a standard sand/cement 19 mm render, with an estimated 30 year lifespan. The main contribution in the use stage is the air source heat pump. Data for the 6 kW heat pump was derived from an industry association Product Environmental Passport, representing a number of mainstream brands. The PEP assumed a 17 year lifespan for the heat pump, which therefore meant three replacements within the sixty year timeframe, and an embodied carbon total of 8.8 tonnes. The analysis assumed that while the first heat pump would have leakage (in line with CIBSE TM 65) of conventional refrigerants with a high global warming potential, policy on phasing out polluting refrigerants would have kicked in after this point, meaning CO2e emissions for refrigerants were not included in replacement units. There is a remarkable point of comparison here: the cradle to factory (A1-A3) and use stage (B) emissions for the heat pump
Walls 12.5 mm plaster 215 mm blockwork 8 mm scratch coat 200 mm EPS 450 x 150 mm PUR 10 mm adhesive 20 mm brick slip Floor 75 mm screed 200 mm concrete (50% GGBS) 250 mm EPS150 A1-A3 (materials only, cradle to factory gate): 13.8t CO2e A1-A5 (cradle to practical completion): 19.5t CO2e A-C (cradle to grave): 21.4t CO2e Stored CO2: -1.1t CO2e
come in at 8.7 tonnes, compared to 9 tonnes for the external walls and floors of Upgrade 3, the timber frame variant. Heat pumps have an important role to play in decarbonising heating, but – while embodied carbon data on MEP systems generally is in its infancy, clearly work is needed to reduce the embodied carbon of building services. In part this may be down to assuming longer lifespans, and therefore fewer replacements – and there is some evidence of air source heat pumps lasting far longer than 17 years. Another factor which
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The Renewable Energy Consultant ISO-CORNER
The strength to hang from external wall. ETICS systems maintain integrity, drive performance and target near zero-energy building objectives.
Because their depth is insulation material, EJOT developed a family of fixing products for medium to heavy loads that add strength to the system’s components, or utilise the anchoring properties of the substrate. Very often both.
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All are designed to maintain the thermal performance and bridging criteria set out by PAS 2035.
To know more about EJOT’s EWI fixing solutions contact our ETICS sales engineer Mark Newell firstname.lastname@example.org
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m � -
A–C embodied carbon totals 50 45
Base Case 1a
Base Case 1b
Embodied tonnes CO2e A–C
Walls Plasterboard and skim 25 mm battens @ 600 centres 12 mm structural airtight board 300 mm cellulose in I-beam 22 mm WF sheathing Battens, counterbattens, 12.5 mm cement fibre board 8 mm proprietary silicone render Floor 75 mm screed 200 mm concrete (50% GGBS) 250 mm EPS150 A1-A3 (materials only, cradle to factory gate): 9.0t CO2e A1-A5 (Cradle to practical completion): 13.4t CO2e A-C (Cradle to grave): 14.6t CO2e Stored CO2: -8.5t CO2e
may make a substantial difference is reducing the demand and size of a heat pump, provided it can comfortably meet the building’s actual heat load. The roof build up was common to all variants, consisting of a standard trussed roof with cement fibre slates, and mineral wool insulation at ceiling level. Internal walls consisted of a timber stud walls insulated with mineral wool and finished with plasterboard, and the intermediate floor included a metal web joist, mineral wool insulation, plasterboard
Kg CO2e/m2 GIA
Embodied Kg CO2e/m2 GIA
beneath and chipboard above. The constant elements – roof, internal walls and intermediate floor, windows and heat pump – add 6.9 tonnes to the module A emissions, 15.3 tonnes to the cradle to grave (A-C) total, and sequester 5.4 tonnes. Further reductions could have been made from the constant elements by a number of measures such as reductions in the number of replacements of heat pumps, choosing a window spec where 60-year lifespan may be reasonably assumed, switching to cellulose insulation for the roof and switching to a thinner calcium sulphate screed. If more radical changes were considered – such as using cellulose insulation in the floor and using ground screws instead of concrete foundations – additional significant reductions could have been achieved. There is also an interesting question of whether improving the fabric to the passive house standard – utilising low carbon materials – would have achieved further reductions, by enabling the use of a smaller heat pump and reducing or potentially removing the need for underfloor heating or other heating emitters. It’s important to note that this analysis was not attempting to produce a like for like comparison between typical cavity wall builds and other approaches. Rather the emphasis was on taking a base case where there has been no particular focus made to reduce embodied carbon use, and to explore what kinds of reductions could be made by switching to relatively mainstream alternatives, supported by certification attesting to their longevity and fitness for use. Further analysis may also involve consideration of other build systems such as insulating concrete formwork, light gauge steel frame, mass timber, poroton blocks, and less mainstream approaches such as hempcrete and strawbale construction. Notwithstanding the health warnings over some of the limitations in this analysis, it demonstrates some of the significant differences in embodied carbon that can result from changes in build specifications at design stage. Whole building cradle to grave emissions The differences between the various build methods look less pronounced when the
whole building calculations are included, rather than the walls and floors only, because the constant elements add significant amounts to the totals. The worst performer, Base Case 1B, totals 43.9 tonnes of CO2e, while the best performer, Upgrade 3, totals 30.8 tonnes. It’s useful to compare the six variants against the embodied carbon targets in RIBA’s revised 2030 Climate Challenge, albeit with the major caveat that not all of the elements of the building have been included in this analysis. The worst performer, Base Case 1B, totals 526 kg CO2e/m2 gross internal area (GIA). In the author’s view, having consulted with building LCA experts, this means it may meet the 2030 target for residential/domestic buildings of 625 kg CO2e/m2, once the missing elements are included. The best performer, Upgrade 3, comes in at 369 kg CO2e/m2, indicating it would likely comfortably surpass the 2030 target. The author speculates that Base Case 1A and Upgrade 1, which respectively total 496 and 492 kg CO2e/m2, would also comfortably meet the target, once the missing elements are included. This begs the question: if a notional house built with business-asusual build specs can potentially meet a forward-reaching embodied carbon target, does the target need tightening?
With thanks to the Passive House Association of Ireland for commissioning this analysis, to Andy Simmonds and Tim Martel of the AECB for conducting the analysis in collaboration with the author and John Morehead, and to Cork City Council’s architect’s department for providing a house type to analyse. Thanks are also due to industry sources who fielded awkward technical questions, including Jane Anderson of Construction LCA, Jess Hrivnak of RIBA, Peter Seymour of EPD consultants EcoReview, Simon Sturgis of Targeting Zero LLP and numerous others.
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PA S S I V E H O U S E +
Marketplace News Lancaster student wins eco design award
CVC Direct launch MVHR addon for space heating & cooling
he School of Architecture from Lancaster University and Ecological Building Systems UK formed a partnership in 2021 to award the best eco-design produced by first year students of the BA (Hons) Architecture at the university. The award went to Katie Phillips, her designs and portfolio showed that she was clearly thinking about usability and functionality, and considered how this can integrate with the building structure and ventilation proposals. Ecological Building Systems provided a prize of a one-year membership to the UK Passivhaus Trust and a subscription to Passive House Plus magazine. Ecological Building Systems general manager Penny Randell said: “We were delighted to work with Lancaster University to create the Eco-Design Award. We like to do as much as we can as a business to support and invest in the future generation of architects, particularly at this critical time as we move towards net zero carbon in the UK, and of course we’d always encourage students to incorporate natural building materials. I am also particularly aware how difficult it can be to recruit technical staff locally at our head office in Cumbria, so supporting a relatively local university is important for us. We hope that the prize given to Katie relating to all things passive house, helps to encourage her to develop these principles within her career.” Course leader for the BA (Hons) Architecture, Dr Ana Rute Costa, said: “We are very pleased to develop this partnership with Ecological Building Systems. Setting a new course of architecture at the university is quite challenging, but also a really exciting opportunity to shape the future of architecture. Creating a supportive network of professionals, academics, industry and community is essential to respond creatively to what the market – and planet – demands.” • (above) Katie Phillips receiving her award, presented by Ecological Building Systems for the best eco-design portfolio produced by first year students of the BA (Hons) Architecture at Lancaster University.
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echanical ventilation with heat recovery (MVHR) systems are an efficient way of providing the necessary ventilation with very few heat losses for airtight dwellings. However, MVHR systems can also be used for space heating or back up heating. For a passive house with a peak load of only 10 W/m2, using your MVHR system to provide both heating and cooling seems like a really good idea, as this is a system that is already required due to the airtightness of passive houses. With the above in mind, CVC Direct have launched a new product from Brink called the Air Comfort. The Air Comfort works as an add-on to the MVHR system and can provide both heating and cooling when provided with hot or chilled water from your central heating and cooling unit. The system can be connected to almost any hot water system, for instance the central heating boiler, district heating, or a reversible heat pump. “Here at CVC Direct we are committed to renewables so we decided to also partner with Stiebel Eltron and offer air source heat pump solutions which can easily be integrated with the Air Comfort system,” said Vitor Roriz of CVC Direct. Because there is a limited amount of
heat that can effectively be transferred with air, and passive house guidelines suggest that the number of air changes per hour for an MVHR system should be kept to a minimum in order to reduce heat losses, the Air Comfort allows you to recirculate some of the indoor air, up to a maximum air flow (fresh and recirculated air) of 450 m3/h. “So we can effectively increase the total heat or cooling we can provide while not changing the total air changes in the house with the outside,” Roriz explained. To achieve a perfect interior climate with a constant room temperature, the recirculated air flow is automatically adjusted according to the discharge temperature. “Here at CVC, if the PHPP calculations show that heating or cooling via the MVHR is feasible, we will design and commission your MVHR and Air Comfort to offer exactly the right amount of heating or cooling necessary to ensure thermal comfort, and that overall relative humidity is at the required level.” • (above) CVC Direct have launched the Air Comfort, pictured here with a Brink Flair 325 MVHR unit, to enable heating and cooling to be provided via the ventilation system in passive houses.
PA S S I V E H O U S E +
Ecomerchant launches three new eco building products
eading sustainable product merchant Ecomerchant is offering three new eco building products to the market. The first is Faay HV84 Indoor Climate Wall, a strong, rapid-install partition wall system made from 100 per cent natural materials (flax, wood fibre and timber). It is installed using the Faay track system. “HV84 is a breathing wall that helps to improve indoor air quality, thermal performance and noise reduction. It is quick and simple to install, and brings a new level of flexibility and savings for partition walling across new build and retrofit,” Will Kirkman of Ecomerchant told Passive House Plus. The product consists of a dense flax core with a factory-bonded wood fibre surface, onto which a natural, breathing finishing layer of the customer’s choice is applied, such as lime or clay plaster. The second new product from Ecomerchant is SkamoWall, a calcium silicate board which absorbs moisture present in buildings by actively diffusing it through the material, where it is safely and harmlessly locked away. Kirkman said: “Over time, in a traditional wall build up, dampness builds up as it is held onto, or trapped within, the wall structure, and this penetrating damp is what causes the development of mould and mildew. “By using SkamoWall Boards the dampness is absorbed and held harmlessly by the board to be later released by evaporation, helping to prevent persistent damp problems.” Kirkman explained that when the relative humidity in the internal space lowers, the drying surface attracts stored water from within the board to the surface, and this is then evaporated safely away in a controlled manner into the internal space, leaving the surface dry once again. For this to be effective, it is important that the room is effectively ventilated. The alkaline composition of SkamoWall Board (pH of 10.3) means that mould cannot form on its surface. The boards can be applied to a wide range of solid mineral surfaces including brick, concrete and blockwork. The boards are not suitable for application to wooden surfaces or studwork. Finally, Ecomerchant is also now supplying Breathe carpet underlay, which is made from natural wood fibres, and has the ability to filter even the smallest dust particles to improve indoor air quality. “Remarkably, tests have shown Breathe filters over 95 per cent of dust out of the air you breathe, trapping even the smallest particles as air passes through for a fresher-feeling home – and making life easier for allergy sufferers too,” Kirkman said. For more see www.ecomerchant.co.uk. • (above) Ecomerchant’s new products include SkamoWall calcium silicate boards (main image), Breathe wood fibre carpet underlay and Faay HV84 Indoor Climate Wall (both inset).
Forbo joins World Green Building Council corporate advisory board
orbo Flooring Systems has joined the World Green Building Council’s (WorldGBC) corporate advisory board. The WorldGBC corporate advisory board is a select group of global leaders in sustainability, active in the building and construction industry. These companies serve to guide WorldGBC on its strategy and activities to accelerate the sustainable building movement. As a global provider of premium commercial and residential floor coverings, sustainability is a major part of Forbo’s ethos; from how it chooses its raw materials to the way it markets and sells its products. By using green design guidelines, green energy and the 4R principle of: reduce, reuse, recycle and renew, Forbo is able to fulfil its mission to create better environments. The company said it has also managed to develop a truly CO2 neutral flooring solution from cradle to gate called Marmoleum, without buying carbon credits. “This real and unique achievement is fuelling its further sustainability ambitions,” a company statement said. All of Forbo’s manufacturing sites are SA8000 certified, one of the world’s pre-eminent social standards, designed to ensure that everyone in the supply chain is cared for, from employees to suppliers. WorldGBC CEO Cristina Gamboa said: “We are thrilled to welcome Forbo Flooring Systems to the World Green Building Council’s corporate advisory board (CAB) for 2021. Through their demonstrations of market leadership towards sustainable building and construction practices, we know that they will bring a wealth of expertise and will be a huge asset to the CAB. We look forward to collaborating over the coming year to deliver sustainable buildings for everyone, everywhere.” Forbo Flooring Systems director Edo Rem said: “We are proud to be recognised for our efforts in creating better environments. Our sustainability goals show a remarkable match with those of the WorldGBC. With our entry to the CAB, we see a great opportunity to actively contribute to green buildings beyond the scope of our company. By working together on a global scale, we believe that we can advance towards a greener built environment with real solutions for decreasing carbon dioxide emissions and achieving circularity, while realising better indoor health and wellbeing.” •
Forbo’s Marmoleum flooring is certified as CO2 neutral from cradle to gate.
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PA S S I V E H O U S E +
PARTEL LAUNCHES NEW EUROCLASS A2 FIRE-RATED VAPOUR CONTROL SYSTEM
Cem-Rock offers best-in-class fire & eco credentials Greenspan L
artel’s newly launched Euroclass A2 Izoperm Plus vapour control system, designed for internal applications in energy efficient buildings, has become the first fire-rated solution in this class developed in Ireland. The system is comprised of Izoperm Plus FR vapour control layer plus Echoseal Alu FR adhesive tape. As a passive fire protection solution, the system is designed to safeguard critical structural components, and to slow and confine a fire once it has started, providing “outstanding fire safety and smoke protection for both occupants and construction assets”, according to Partel. The system was tested to and successfully received the Euroclass Class A2-s1, dz0 standard in accordance with EN 13501-1, making it ideal for taller buildings. “High-rise structures, by their very design, pose particular fire-safety issues. As a result, building codes for high rises emphasise fire-resistant construction. Our integrated technical solution was explicitly built in response to evolving building requirements to be Class A2-s1, dz0 fire-rated — facilitating designers, architects, and building professionals to achieve modern resilient buildings,” said Hugh Whiriskey, founder and technical director of Partel. Partel said that its high-performance membrane and tape uses an innovative technology based on lacquered aluminium laminated with strong glass fibre. Both aluminium and glass fibre are non-combustible, ensuring excellent fire resistance, the company said, and this unique composition guarantees superior structural integrity and durability alongside a high mechanical resistance and maximum airtightness. Izoperm Plus FR acts as an air and vapour control layer, preventing condensation and improving energy efficiency in building assemblies. It is suitable for all construction types, especially mid and high-rise public buildings such as offices, hospitals, schools, and shopping centres where building codes recommend a higher level of fire safety. The system has been extensively tested in accordance with EN 13823 (single burning item test) and has successfully received the Class A2-s1-d0 standard in accordance with EN 13501-1. In this case, s1 indicates the highest performance category for minimum smoke production if ignited by a fire, and d0 represents the highest performance category with regards to the potential for hot droplet/ particle production. “The system comes with an unmatched 20-year warranty and uncompromising quality from Partel,” Hugh Whiriskey said. For more information see www.partel.ie. • (above) Partel’s Izoperm Plus vapour control system has achieved a Euroclass A2 fire rating.
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eading Limerick and Birmingham-based sustainable building product supplier Greenspan has added a floor substructure board to its Cem-Rock range of magnesium oxide (MgO) sheathing boards. “Cem-Rock is mainly geared to be used as a sheathing board for larger buildings, and for mid and high-rise construction,” Mike Cregan, managing director of Greenspan, told Passive House Plus. “We find it’s very popular because of its excellent fire performance and because of its tremendous structural and sustainability credentials. It also has excellent pull out resistance and racking strength, making it ideal for use on timber frame construction.” Designed as an alternative to traditional fibre cement or OSB/ plywood boards, Greenspan launched Cem-Rock in 2013. Cregan said that the board’s “fire, moisture, mould and mildew resistance properties far outweigh any competing products like plywood or OSB sheathing” and that its performance is unaffected by environmental exposure during construction. The company has developed different variations of the product to be used as exterior sheathing boards, external insulation substrate boards, and rainscreen backer boards. The newest iteration is Cem-Rock Floor. “Cem-Rock Floor has structural and bending characteristics similar to plywood, and Cem-Rock Floor has been tested for its load bearing capabilities making it suitable for all classes of buildings,” Cregan added. Cem-Rock is produced from magnesium oxide, a white hygroscopic solid mineral, together with binders such as perlite and wood dust. The material is inert and fully recyclable. It is manufactured using a cold process that is powered entirely on electricity, so can be fully powered by renewables, and requires no firing or autoclaving, thus minimising carbon emissions. “Cem-Rock Floor also offers best-in-class fire performance,” Cregan said, “making it a popular choice for large buildings such as apartments, commercial, student accommodation and high rise where fire performance is critical”. It has achieved Euroclass A1 non-combustibility rating according to BS EN 13501, and Cem-Rock achieves more than two hours of fire resistance on wall partitions according to BS EN 476 parts 20 and 22. Cem-Rock has also recently become the first Irish brand of MgO boards to enter the US market. For more information see www.cemrock.ie. • (below) Cem-Rock Floor, the newest addition to the Cem-Rock magnesium oxide board range.
PA S S I V E H O U S E +
Soprema launches insulation made from recycled jeans
Munster Joinery publishes first Irish window EPD
oprema is turning workwear into sustainable insulation with its launch of Pavatextil P, a versatile material made from recycled cotton and denim, and with “superb thermal performance and buildability benefits”. The company said that the new product drives forward its “circular construction approach to developing products that utilise recycled materials to reduce waste, offer a sustainable supply chain and answer increasing demand for credible, environmental solutions”. To produce Pavatextil P, selected cotton and jeans are unravelled and reused in an “ecologically optimised production process” that is powered by renewable energy, the company said. The recycled cotton fibres are then processed into soft insulation panels. Pavatextil P also provides excellent acoustic insulation and boasts an A+ rating for VOC emissions. Roland Jackson, commercial director of Soprema UK, said: “Soprema is a pioneer in developing sustainable construction concepts and transforming those ideas into products that offer environmental, buildability and performance benefits. “With Pavatextil P, we have delivered those principles in a way that’s accessible for everyone – anyone who has ever owned a pair of jeans could potentially be part of this innovative approach to recycling a ubiquitous consumer product into a high-performing element of a more sustainable built environment.” In addition to its environmental and performance benefits, Pavatextil P also offers significant buildability advantages, according to Soprema. Light and flexible, the material is simple and easy to cut to size and shape on site and can be installed quickly and easily between roof beams, under floorboards or in stud walls and partitions. The material can also be installed in layers to tailor the installation to the required thermal performance and property design. Roland Jackson added: “Denim has been chosen as an ideal recyclable material by Soprema thanks to its durability and flexibility. Indeed, American gold diggers chose jeans because they were the strongest trousers they could find. Now, even when jeans are worn out, the ultra-tough fabric can be repurposed as insulation material, giving them a second life. “A good pair of jeans can last for years but Pavatextil P can last for generations while providing a more comfortable, energy efficient and sustainable built environment. We believe it is a game changer in the way the construction sector will think about sustainability and the use of recycled materials in the supply chain.”• (above) Soprema’s new Pavatextil P insulation is made from recycled cotton and jeans.
unster Joinery has published the first environmental product declaration (EPD) for a window under the Irish EPD system. The EPD was published for the company’s Passiv uPVC window and is available to view on the Irish Green Building Council’s EPD database. “This EPD has allowed Munster Joinery to measure its performance and set goals in regard to sustainability while demonstrating our commitment to reducing carbon emissions,” said Marlene O’Mahony, quality manager with Munster Joinery. “We expect to publish EPDs for our other product ranges in the coming months.” An EPD is a standardised report containing data on the environmental impacts of a product or material over its lifetime. This data provides construction industry professionals with a transparent source of information, allowing the comparison of different products under a common set of environmental performance indicators. The EPD is based on data generated by a life cycle assessment (LCA), which can measure the sustainability of the product across various stages – production, installation, use and end of life. The production stage assesses the impacts of raw material supply, transport and manufacturing. Seven different impact categories are used: climate change, depletion of abiotic resources (both fossil fuel and elemental), ozone depletion, photochemical oxidation, acidification of land and water, and eutrophication. As the availability of EPDs for construction products increases, specifiers will be able to access quantified environmental information detailing the impacts of materials in buildings. This will allow more informed decisions in procurement. “Munster Joinery aim to be at the forefront of this drive to make accurate, unbiased sustainability data available to the market,” O’Mahony said. “This reflects our wider sustainability policy. All our product ranges meet NZEB requirements as a minimum and eight product lines are certified by the Passive House Institute in Germany. We aim to make sustainability, carbon neutrality and energy efficiency accessible to the built environment. “Our operations are tailored to minimise the use of energy and water, use materials that are environmentally friendly, use recycled materials wherever possible, minimise waste and continually reduce emissions. “Much of our energy needs are met by two wind turbines with an electrical output of 4.2 megawatts. A biomass combined heat and power (CHP) plant with a capability of 12 MW thermal and 3 MW electrical also contributes significant amounts of green energy to the plant.” •
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PA S S I V E H O U S E +
IG MASONRY SUPPORT CLAIMS “CARBON NEUTRAL” STATUS
nnovative manufacturer of brickwork support systems IG Masonry Support has become the first company in its sector – and the first company in the Keystone Group – to achieve “carbon neutral” status. As a group committed to reducing the environmental impact of all operations, other companies within Keystone are now taking the necessary
steps to achieve carbon neutral status. IG Masonry Support’s sustainability journey began in 2018. Year on year the company has implemented sustainability initiatives, including upgrading forklift trucks to electrically operated systems and having zero per cent waste sent to landfill. Earlier this year, carbon neutral certification was awarded to the company’s BOSS A1 brick on soffit system product, a goal which formed one of the first steps in the company’s commitment to bringing innovative products to the marketplace in the most sustainable, carbon neutral way. Speaking of IG Masonry Support’s latest achievement, IG Masonry Support managing director Andy Neal said: “We take our environmental responsibility seriously and are making the necessary changes within our business practices to become a net carbon zero company. I am proud that we have now achieved carbon neutral status and are the first masonry support manufacturer in the UK to reach this goal. It is testament to our team’s passion and commitment to operating a sustainable business and to delivering sustainable products and solutions to our marketplace.” Amidst many initiatives implemented by IG Masonry Support, such as switching to a 100 per cent renewable energy tariff, the company is continuing to proactively reduce its carbon footprint alongside the SBTi (Science Based Targets Initia-
tive) methodology. This methodology drives ambitious climate action in the private sector by enabling companies to set science-based emissions reduction targets. For IG Masonry Support, identifying Scope one, two and three emissions provided clarity of the environmental impact across all operations and raised opportunities for carbon reductions. As the company sees its emissions plummet following the SBTi, IG Masonry Support is on track to play its role in achieving the 1.5 degree Paris Agreement target. Going forward, IG Masonry Support has pledged to continue to address all areas for improvement with a sustainably-focussed supply chain, helping to source its responsible future. IG Masonry Support pledges to develop products that provide environmentally significant solutions to its customers and end users, among other goals including a conversion to 100 per cent electric fleet by 2025. It will also develop environmental product declarations (EPDs) for its product portfolio, providing transparent and comparable information about the life-cycle environmental impact of its products. Doing so will empower the business and its people to make and adhere to the changes that are needed to reduce impact on the environment. • (above) IG Masonry Support managing director Andy Neal.
Xtratherm announce agreement in principle to acquire Ballytherm’s operations in Ireland and the UK L eading insulation manufacturer Xtratherm has announced the signing of an agreement in principle to purchase Ballytherm’s operations in Ireland and the UK. The company said the acquisition is in line with its strategic growth ambition and will bring additional manufacturing capacity and the newest PIR manufacturing facility in the United Kingdom. “The acquisition will complement and enhance our offering and will create the most innovative and comprehensive insulation offering in the UK and Ireland, increasing our capacity, and contributing to our drive for a more sustainable business model,” a statement from the company said. “This expansion greatly enhances Unilin Insulation’s operations in the UK and Ireland where currently, through Xtratherm, they
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offer a wide and innovative range of insulation technologies to customers.” Ballytherm currently manufactures PIR insulation products in Ballyconnell, Ireland and plans to do so soon at its new state-of-theart manufacturing facility in Ross-on-Wye, UK. In commenting on the acquisition, Barry Rafferty, Xtratherm MD said: “Xtratherm has experienced steady growth since 2015 when it became part of the Unilin Group. The acquisition of Ballytherm, along with additional investment in new technologies will allow Xtratherm to deliver on operational excellence, new product innovations and improved service that will contribute towards a stronger and more sustainable future for our employees, customers and the construction sector in the UK & Ireland.”
Lieven Malfait, president of Unilin Insulation and member of the Unilin Group executive committee, said: “I am delighted to welcome our new colleagues from Ballytherm to our group. We are fully committed to strengthening our position as a European leader in our markets, and this agreement is an important step forward.” The deal will be notified to the Competition and Consumer Protection Commission in Ireland, and so is subject to its approval. The parties anticipate that the deal will be closed towards the end of 2021. Xtratherm was founded in 1986 and became part of the Unilin organisation in 2015. It owns and operates two state-of-the-art production facilities in the UK and Ireland manufacturing PIR, Phenolic and EPS insulation. •
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T O BY C A M B R AY
On the 3D printing of buildings Building physics expert Toby Cambray finds himself unconvinced by the merits of a new home in the Netherlands that has been 3D printed with concrete.
o the already long list of unfashionable opinions which I have put forward, I need to add the following: when it comes to 3D printing, I can’t see what all the fuss is about. Sure, it’s a useful means of making prototypes, and the small number of one-off products or parts that need very little strength – but there seems to be a distinctly finite number of those. 3D printers mostly seem to churn out little toy boats more likely to pollute our oceans than sail on them. Some argue that 3D printers are inexpensive enough to represent a democratisation of the manufacturing process, but I don’t buy it. There is still a skill threshold to reach in the digital design stage, time which one could spend learning how to use a metal working lathe, hobby versions of which aren’t much more money than a half decent 3D printer. Or think of the stunning architectural models that have been made with little
Proper sustainable building is all about the boring stuff.
more than a craft knife. So, while 3D printing is an interesting tool to add to our collective arsenal, the popular obsession with it is baffling to me. You will be therefore unsurprised to read that I have reservations when it comes to the recent flurry of attention around 3D printed buildings. The one doing the rounds on the socials at the time of writing is the Dutch “boulder house” featured in the Guardian (30 April 2021). This detached house is the latest in a string of prototypes and is designed to resemble a boulder. Exactly which boulder served as a model has not been disclosed. I understand that the process is still in development, but if this is the sort of architectural expression we can expect to be unlocked, I am unmoved. Even if more ‘interesting’ shapes become possible, are they a good idea? Frankly, assuming for a moment that such forms are so essential to architectural expression, all this is possible with more boring techniques. Then there is the subject of form versus function in passive
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The recently completed ‘boulder house’ in Eindhoven.
buildings, which I won’t rehash here. This is Passive House Plus after all, so we turn next to the thermal performance. Those involved are coy about the exact performance, and though I’d be delighted to be proven wrong I doubt that the energy performance is being measured. It’s difficult to find out exactly how the walls work in the Dutch example, but we can see in Matt Risenger’s recent video (‘Is this the future of Construction? 3D Concrete Printed Homes’, YouTube, 4 May 2021), that we have two leaves separated by a zigzagging ‘core’ like an extruded truss-joist. The window reveals are formed by simply continuing the leaves from inside to out. I therefore raised an eyebrow when the engineer claimed the construction to be ‘thermal bridge free’. In other words, as far as I can tell, to actually add insulation to any of these structures, you’d have to stick it on the outside afterwards (and clad to taste), which seems to defeat the object somewhat. Airtightness wise, OK it is monolithic but it’s at junctions (windows, floor, services) where one finds leaks, so I’m unconvinced the method of construction is inherently airtight. As printed, the internal walls are rough, but Matt Risenger assures us it’s not a bug, it’s a feature. Anyhow, good luck keeping all those crevices clean. We should also consider the claim that this technology speeds up construction. I’m willing to accept it might save some time on the superstructure compared to standard masonry, but anyone that has experienced a build from beginning to end knows that the superstructure is far from the most time-consuming element – it’s the groundworks, services, fixtures and fittings and finishing that take the real time.
Finally, there is the issue of embodied carbon. Most of the examples I’ve seen are some sort of very clever concrete, though an earth-based example has also been finished (with only a tiny bit of ‘binder’). The builders attempt to justify the Dutch example by observing that we must use less concrete, and the boulder house uses less. I’ll go out on a limb and say maybe – stay with me – you might use less concrete if you didn’t build the entire house out of it. The waste of resources is perhaps the most frustrating thing – not just the concrete but the human effort. I’ve no doubt that it was a great technical achievement to develop this technology, but it has the feel of a solution looking for a problem. One of those ideas that look great in the sketch book and are sexy enough to get some cash thrown at them, but aren’t really moving us forwards. In contrast, proper sustainable building is all about a solid strategy, the fine detail and quality of execution – some might say, the boring stuff. If you’re reading this magazine, you probably know all this and spend your time worrying about precisely which type of airtightness tape is best to join material A to material B, rather than whether we can equip a drone with a tube of silicone. And I salute you and your quiet dedication to getting on with delivering sustainable buildings. n
Toby Cambray is a founding director at Greengauge and leads the building physics team. He is an engineer intrigued by how buildings work and how they fail, and uses a variety of methods to understand these processes.
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The renewable heating alternative
Serious about sustainability The Ultra Quiet Ecodan range of air source heat pumps from Mitsubishi Electric are some of the most advanced heating systems available. Designed specifically for UK conditions, Ecodan provides renewable, low carbon alternatives to traditional fossil fuel-burning heating systems. With an A+++ ErP Rating label across the range, homes can be heated for less while cutting CO2 emissions.
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