Passive House Plus (Sustainable building) issue 46 UK

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

HANDLE WITH CARE Exeter extra care scheme goes passive to protect the elderly

MUCH ADO ABOUT NOTHING Is zero carbon construction Carbon first, fabric second

How to decarbonise the UK’s housing stock

Play to win

Creative play café brings passive benefits for Bristol families

A Robin Hood energy policy

Give to the frugal, take from the profligate

46 C outside, cool inside

Seville hotel beats the heat with passive retrofit

Issue 46 £5.95 UK EDITION

even possible?

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EDITOR’S LETTER

PASSIVE HOUSE+

Publishers Temple Media Ltd PO Box 9688, Blackrock, Co. Dublin, Ireland t +353 (0)1 210 7513 e info@passivehouseplus.ie www.passivehouseplus.co.uk

Editor

Jeff Colley jeff@passivehouseplus.ie

Reporter

John Hearne john@passivehouseplus.ie

Reporter

Kate de Selincourt kate@passivehouseplus.ie

Reporter

John Cradden cradden@passivehouseplus.ie

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Art Director

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Design

Aoife O’Hara aoife@evekudesign.com | evekudesign.com

Contributors

Lenny Antonelli journalist John Butler Passivhaus Consultant Toby Cambray Greengauge Building Energy Consultants Juan Manuel Castaño Castaño & Asociados Passivhaus Marc Ó Riain doctor of architecture Andrew Simmonds Simmonds.Mills Architects María Vico Castaño & Asociados Passivhaus Jason Walsh journalist

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editor’s letter I

f 2023 was an annus horribilis for the planet, then December was the finis horribilis.

While negotiators were attempting to broker a deal to limit warming to 1.5 C above pre-industrial levels (1850-1900) at COP28 in Dubai, EU scientists confirmed that 2023 would be the warmest year on record, based on the global mean temperature for the first 11 months of the year. But how high was that temperature compared to 1850-1900 levels? 1.46 C. Think about this for a second. At a time when global emissions from fossil fuel use continue to increase – effectively pouring a hydrocarbon on a fire – the only thing that kept the world below the 1.5 C limit in 2023 was the fact that we go two places past the decimal point.

Of course, it should be said that this is just one year, and these are preliminary estimates. If we are to look for crumbs of comfort, we may find them in the hope that some climate scientists cling to – that an enormous sudden drop in emissions may keep 1.5 C within reach. But step back and look dispassionately at the situation. COP28 was held in a petrostate, presided over by Sultan Al Jaber. This is a man whose day job is chief executive of the United Arab Emirates’ state oil company, ADNOC. “There is no science out there that says that the phase-out of fossil fuel is what’s going to achieve 1.5 C,” Al Jaber said in the run up to the event, adding that phasing out fossil-fuels would not allow sustainable development “unless you want to take the world back into caves.”

In that context, you might consider it a blessing that COP28 led to any kind of agreement at all that even green politicians felt they could sell to their electorates, but

ISSUE 46 it’s hard to escape the feeling that the kind of radical action that the world needs will not stem from this agreement. We may already have reached the point where 1.5 C is no longer attainable.

This is not to throw in the towel or wallow in despair. The risk of reaching climate tipping points notwithstanding, we must beware of conceiving of our lot in simplistic binary terms of doom or salvation. The fact is that every fraction of a degree of warming that we can prevent is worth fighting for.

The power to stop a bad situation from getting worse – or limiting how much worse it gets – is still within reach.

True, the enormousness of the challenge facing humanity can be overwhelming. But there are signs of hope. Land use emissions are falling, albeit modestly. And fossil fuel-related emissions are falling in some regions, including Europe and the USA. With the developed world, the clue is in the name. Profligate, uneven and environmentally destructive though our development may have been, we do not need to create the systems required to give most people a reasonable standard of living. Rather, we need to radically adapt how we think and act to reduce our impacts on the planet.

For my part, as we head into a new year I will take inspiration in the stories we have the privilege of telling in Passive House Plus: stories of people making profound improvements to the places where ordinary men, women and children live, work and play, and in so doing prove that we do not need to keep destroying the conditions that sustain us in our attempts to improve our lives.

Regards, The editor

Cover

Edwards Court, Exeter Photo by Architype

Publisher’s circulation statement: Passive House Plus (UK edition) has a print run of 9,000 copies, posted to architects, clients, contractors & engineers. This includes the members of the Passivhaus Trust, the AECB & the Green Register of Construction Professionals, as well as thousands of key specifiers involved in current & forthcoming sustainable building projects.

Disclaimer: The opinions expressed in Passive House Plus are those of the authors and do not necessarily reflect the views of the publishers.

Official partner magazine of: • The Association of Environment Conscious Building

• The International Passive House Association

• The Passivhaus Trust

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CONTENTS

PASSIVE HOUSE+

CONTENTS COVER STORY

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NEWS Sustainable bodies criticise Future Homes lack of ambition; free training programme developed to provide UK architecture students with a solid foundation in climate-responsive building design; and Scotland committed to continuing passive house journey.

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COMMENT Shortlisted for the Stirling Prize in 2003, BedZed was a prominent example of architecture starting to pay attention to sustainability. But how well did it work? In the latest part of his series on the history of low energy architecture, Dr Marc O’Riain looks back at a landmark project.

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Handled with care

Exeter extra care scheme goes passive to protect the elderly If thermal comfort is important for people of all ages, it’s even more so for elderly people, for whom the right living conditions can be a matter of life or death. Passive House Plus visited one award-winning extra care facility in Exeter to learn how the decision to go passive was working out for the residents.

The first passive house certified hotel in Seville’s historic centre defies the challenges posed by its hot climate, small size, and preservation requirements, showcasing innovative strategies to mitigate heat and maximize energy efficiency.

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CASE STUDIES

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Play to win

Creative play café brings passive benefits for Bristol families A site with a dilapidated building in Bristol has been transformed into a crucial social space by a husband and wife team of environmentally- and socially-engaged architects, aided by a polymath sustainability consultant.

Bungalow bills

Monaghan retrofit takes passive route to low costs and high comfort What does it feel like to suffer the cold, mould and discomfort of a 1960s bungalow, and experience its rebirth as a passive house? The owner of one award-winning project spills the beans.

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Home from home

Architect turns childhood home into client’s passive house Few architects are tasked with knocking their old family home, but for John Morehead, once this difficult decision was made, it was a chance to create a future-proofed new passive house that embraces its stunning natural surroundings and exhibits remarkable attention to detail.

INSIGHT

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Much ado about nothing

Is zero carbon construction actually possible?

As the world edges ever closer to the precipice of runaway climate change, some sustainability terms have moved from relative obscurity towards the mainstream of marketing and public discourse – and none more so than zero carbon. But is zero carbon construction a real prospect, or is it just wishful thinking?

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Carbon first, fabric second

How to decarbonise the UK’s housing stock Rapidly decarbonising our cold, leaky dwellings is the greatest challenge facing the building industry, one fraught with complexity and risk.

Given that the UK faces similar challenges to Ireland – in a similar climate, with similar housing stock – what can we learn from British efforts to meet this challenge? Leading UK green building association the AECB has put forward a proposal that could help to chart a new course through these choppy waters.

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MARKETPLACE Keep up with the latest developments from some of the leading companies in sustainable building, including new product innovations, project updates and more.

A new energy policy: give to the frugal, take from the profligate

Should we look to Robin Hood to help transform energy use in buildings? New proposed reforms to how energy is priced could hold the key to discouraging excessive energy use, stimulating retrofit and driving down carbon emissions, argues Toby Cambray.

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CONTENTS

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TRIANA HOUSE

BIG PICTURE

BIG PICTURE PASSI VE & ECO BUIL D S F R O M A R O U N D TH E WO R LD With climate change leading to increasingly frequent and intense heatwaves across much of the world, parts of southern Europe have suffered more than most. In the historic Andalusian city of Seville, the mercury has been hitting 46 C. How do you keep a building cool in those conditions without putting enormous strain on air conditioning systems? One existing boutique hotel may have hit the answer – with a passive retrofit.

by Juan Manuel Castaño and María Vico, Castaño & Asociados Passivhaus

1. Triana House boutique hotel: a passive house icon in Andalusia The first passive house certified hotel in Seville’s historic centre defies the challenges posed by its hot climate, small size, and preservation requirements, showcasing innovative strategies to mitigate heat and maximize energy efficiency. Through meticulous design considerations, including strategies to minimize cooling demands, Triana House boutique hotel achieves the passive house standard while preserving its traditional Andalusian style.

Triana House proudly claims the title of being a trailblazing pioneer – the very first passive certified hotel in all of southern Spain.

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TRIANA HOUSE

2. The original idea Isabel, the driving force behind Triana House, already had another hotel in the same area and harboured an incredibly ambitious goal: to refurbish a newly acquired building in the Triana neighborhood, creating a hotel that would not only set industry standards but also deliver utmost comfort to its guests, coupled with unparalleled ener-

gy efficiency. It was a sustainable endeavor where, beyond the use of natural materials, minimizing pollutant emissions and energy consumption was paramount. It represented an ecological commitment that artfully melded sustainable features with luxury and tradition. The true allure of Triana House lies not just in what it is, but in how it op-

erates, how it feels, and how it appears. It’s a story of dedication to eco-conscious principles while weaving an intricate tapestry of opulence and heritage. The essence of Triana House transcends its physical form; it’s a visual symphony, a testament to sustainable hospitality, and an embodiment of beauty that extends far beyond what the eye can see.

3. Hotel layout overview At 291 m 2 in surface area, the hotel encompasses a basement, ground floor, two additional floors, and a total of seven guest rooms. Notably, the hotel only has a single facade facing the street, which lies to the east, complemented by a traditional Andalusian interior patio. The layout includes a kitchen and plant room situated in the basement, with the reception area and two guest rooms on the ground floor, three rooms on the first floor, and two penthouses on the second floor.

From the outset, this ambitious architectural undertaking had a formidable team of multidisciplinary experts: architect, passive house designer, engineer, interior designers, and a construction team with passive house tradesperson qualifications all came together to make this fantastic result possible.

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TRIANA HOUSE

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4. Enhancing thermal envelope efficiency The street-facing facade, protected by heritage regulations, posed a unique challenge.

External insulation, commonly used for retrofits, couldn’t be installed. As a result, insulation was primarily applied to the interior. Furthermore, in conjunction with interior insulation, the decision was made to implement a 2 cm insulating mortar layer on the exterior.

The U-values and composition varied to address thermal bridging, a necessary concession due to the traditional typology and design of the building.

Some of the envelope enclosure’s U-values on the facade are lower than typical for this climate: the average U-values are 0.29

for the facades and 0.173 for the roof. This adjustment compensates for the building’s shaded location and the thermal bridges that had to be accepted due to the inability to install external insulation.

Certified passive house wooden windows designed for warm climates (with a frame U-value of 1.20) were installed. The glazing features tripleglazing with a U-value of 0.84 and a solar factor (g) of 0.31. The decision to use triple glazing was driven by the shading of the building’s openings, restrictions on enlarging window openings due to heritage considerations, and the need to maintain a low solar factor to reduce cooling demand.

5. Hot climate, cool solutions Triana House, though small with substantial internal heat loads, efficiently meets cooling demands (15 kWh/m2yr) using strategic passive design techniques.

The central patio provides natural shade to every window, aided by a permanent awning during hot summers.

Managing solar radiation is key. Various exterior blinds, from traditional to modern roller blinds in insulated boxes, were used. The aforementioned glass g-factor of 0.31 helps balance cooling without increasing heating demand too much.

To reduce internal heat gains, the mechanical room is placed outside the thermal envelope.

The hotel has a fully automated installation, with smart building technology including automatic external mobile shading in the attic room, optimized time automation on hot water recirculation, and occupancy-based HVAC and ventilation modes.

The building’s three heat recovery units have three modes, considering an average of 0.7 air changes per hour in the building in summer mechanical ventilation.

In addition to dissipating heat, it reduces the indoor humidity.

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Photos: Triana House Boutique Hotel

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SELECTION SOFTWARE 2018

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6. Airtightness challenges The building’s airtightness posed a formidable challenge, given its compact size and the intricate web of installations, including mechanical ventilation with heat recovery, domestic hot water, and a cooling floor, all penetrating the envelope.

The structure was divided into two airtight sections: the basement and the combined ground floor, first floor, and attic.

With access to all spaces from the exterior patio and a complex network of utilities crisscrossing the envelope, achieving airtightness was no small feat.

Throughout construction, seven blower door tests were conducted to assess various elements of the airtight envelope.

These tests encompassed the two independent sectors, installation shafts, twelve exterior doors, windows, and more. To facilitate these tests, one-square metre openings were strategically left between rooms within the sector, extending above ground level until project completion. As the rooms were not interconnected, access was provided through the gallery, a necessity for conducting the airtightness test.

In the end, the n50 result stood at an impressive 0.60 air changes per hour at 50 Pa, marking the triumphant resolution of airtightness challenges in a structure that presented a unique amalgamation of characteristics: open design to a patio, modest proportions comparable to a family house, and the complexities inherent to a hotel’s utility demands.

Triana House’s achievement in airtightness underscores its commitment to both energy efficiency and guest comfort.

7. Mechanical ventilation: blending novelty with tradition The hotel features three passive house-certified mechanical ventilation with heat recovery (MVHR) units that provide filtered, clean, and conditioned air to: 1) the hotel rooms, 2) the basement, and 3) the ground floor’s entrance hall, reception area, and office.

The decision to install three units stemmed from the hotel’s compact size, allowing for a distributed ventilation system throughout the building. The passive house certification required a balancing protocol for all heat recovery units, encompassing three usage modes: minimum, standard, and maximum.

The MVHR system ensures excellent indoor air quality while operating quietly. A significant challenge was harmonizing the novelty of such a system with the hotel’s traditional design. For example, custom-designed air supply vents in the ventilation system blend seamlessly into the room decor, featuring a traditional plaster finish that complements the overall ambiance of the hotel’s rooms and spaces. These vents can be seen on the ceiling in this room’s photograph (left).

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TRIANA HOUSE

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8. Climate control: heating and cooling The hotel includes a combined heating and cooling system composed of air ventilation post-heating / cooling batteries, one for each heat recovery unit and a radiant floor heating / cooling system.

This innovative solution ensures a comfortable year-round interior environment with fully automated operation. Seville experiences exceptionally hot summers (with maximum temperatures reaching 46 C and mild winters, with minimum temperatures occasionally dropping to -5.5 C (averaging 10.9 C).

The cooling strategy includes a low thermal inertia radiant floor system to capitalise on Seville’s relatively arid summer climate. This underfloor system functions for both heating and cooling, and not only eliminates the need for in-room machinery like fan coils or splits, addressing issues of ceiling height and noise, but also offers guests rapid temperature control.

Operating at a refreshing 16 C, the cooling floor yields an impressive 41 W/m 2 (with a total cooling floor power of 9 kW) and boasts an EER of 3.6.

In tandem with this, three support water coils for post-treatment of ventilation air contribute approximately 2 kW each (totaling 6 kW) with an EER of 2.9. Initially, the cooling floor system takes charge, only engaging the water coils in the ventilation system when the desired temperature is yet to be reached. These three units, all passive house certified with an 84 per cent efficiency rating, work seamlessly to cool or heat the ventilation air as required.

Room climate control goes the extra mile, with automated adjustments in place for vacant rooms or instances of doors or windows left ajar for extended periods (monitored through contact sensors).

And for guests, the power to fine-tune the room’s temperature within a 3 C margin rests at their fingertips, all masterfully orchestrated from the reception desk.

According to PHPP calculations, heating and cooling loads are 11 W/m 2, but this is predicated on the occupant using the building as intended. But because the hotel may face extremely high temperatures, and may need to quickly adapt to a wide variety of situations and

occupancy levels on different days – with guests who may leave windows open and not be conscious of how to manage the rooms, the loads were oversized to 68 W/ m 2 to cover all eventualities. The air-towater heat pump installed has a robust 17 kW capacity.

9. Renewable energy solutions in action The hotel relies on a 17 kW air-to-water heat pump for heating, cooling, and domestic hot water (DHW).

Additionally, nine solar panels on the rooftop harness solar thermal energy to warm the water used for both heating and DHW. In case of heightened demand, the heat pump seamlessly kicks into action. Moreover, the system features controlled hot water recirculation. A pump circulates hot water through highly insulated pipes a few times a day to minimise the time it takes for hot water to reach appliances and thereby reduce water wastage.

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10. Elevating comfort and sustainability Staying at Triana House Boutique Hotel offers an unparalleled experience in terms of indoor air quality and comfort.

It is an eco-conscious establishment that prioritizes the well-being of their guests by meticulously controlling and filtering ventilation to ensure a constant supply of fresh and healthy air. The exceptional airtightness and sound insulation of passive house structures create a tranquil and temperature-stable environment, guaranteeing a peaceful night’s sleep and a comfortable stay.

What sets this passive hotel apart is the owner’s commitment to sustainabil-

ity in every aspect. From the materials used in construction to the furnishings and amenities, Triana House prioritizes eco-friendly options. You’ll find bed linens and towels made from sustainable materials, locally sourced products, and high energy efficiency throughout the hotel in all its uses.

This dedication to environmental responsibility not only enhances the guest experience but also contributes to a greener future for the planet. Staying at this hotel means enjoying the highest standards of comfort and well-being while minimizing your ecological footprint.

11. Passive house certification The official passive house classic certification of this hotel is a triumphant step towards sustainability and energy conservation. It proudly champions reduced energy consumption, slashing operational costs and carbon emissions. It champions unmatched indoor comfort, ensuring guests experience a space of pure serenity. Sustainability lies at its core.

This commitment translates into substantial, long-term savings, amplifying the hotel’s environmental responsibility and attracting eco-conscious guests. It stands as a beacon of change, a testament to a future where energy conservation is not a choice but a necessity, and where the comfort of guests and the planet coexist harmoniously.

12. Sustainable hotel and satisfied customers Triana House Boutique Hotel seamlessly blends sustainability with luxury, redefining the concept of hospitality in a historic city.

With a meticulous focus on energy efficiency and environmental consciousness, this architectural gem effortlessly combats Seville’s sweltering summers and ensures a cozy winter refuge. Harnessing clean energy via air source heat pumps and solar panels for hot water and heating generation, it’s a beacon of sustainability.

This hotel is efficient, comfortable, healthy, and environmentally committed, reducing 30 tons of CO2 emissions annually, equivalent to planting 3,000 trees each year. Triana House Boutique Hotel invites guests to indulge in sustainable opulence, ultimately leaving guests with a memorable and environmentally responsible experience.

Discover more about this remarkable oasis in the Passive House Database, ID: 7174.

SELECTED PROJECT DETAILS Passive house assessment: Juan Manuel Castaño / María Vico Castaño & Asociados Passivhaus. www.castanoyasociados.com Architects: Imago Arquitectura Builder: Construalia Hotel website: trianahouse.com

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NEWS

PASSIVE HOUSE+

NEWS Sustainable bodies criticise Future Homes lack of ambition T

hree leading sustainable building organisations have expressed disappointment with the government’s proposed Future Homes Standard, which went to consultation in December, along with proposals for non-domestic buildings.

The Passivhaus Trust, UKGBC and AECB all criticised the lack of ambition in the proposals.

The proposed standard, which will be introduced for new homes in England, includes two options, both of which have identical fabric U-values and an air source heat pump.

Option two features an airtightness AP50 of 5 m3/hr/m2 at 50 Pa and natural ventilation, while option one features a marginal airtightness uplift to 4m3/hr/m2 at 50 Pa, decentralised mechanical extract ventilation, a wastewater heat recovery system, and a solar PV array covering the equivalent of 40 per cent of the ground floor area.

By contrast, the news comes as the EU has just reached an agreement on the next recast of the Energy Performance of Buildings Directive – including zero emission requirements by 2030 for new buildings and 2050 for existing buildings, and a requirement to calculate the whole life carbon emissions of large new buildings from 2028 and all new buildings from 2030, and to set targets to limit whole life carbon emissions by 2030, and develop proposals for climate neutrality.

Commenting on the proposals, Passivhaus Trust CEO Jon Bootland said: “The Passivhaus Trust is disappointed with the proposals being put forward for the Future Homes Standard. We believe that what is being proposed is a missed opportunity to address fuel poverty and the climate crisis and will not deliver what we would consider to be a 'Future Home'.”

UKGBC deputy chief executive Simon McWhirter added: “This can’t genuinely be described as a ‘future’ standard. Having already shattered industry confidence with repeated green rollbacks, the government has opted for the least ambitious option that would deliver ‘future’ homes from 2025 at a lower standard than many homes already built today.”

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AECB CEO Andrew Simmonds said: “This proposal illustrates how government and the loudest voices in the home building industry remain at odds with the need for housing to reliably reduce its energy demand to strategically align with the developing UK low carbon heat and power supply system. Both AECB and Passivhaus Trust members have for years been building to sensible AECB & passive house low energy, low carbon, high-performance new build standards. Why not simply adopt these?”

The AECB also raised concerns about the proposed approaches to ventilation and airtightness and pointed out that while relying on natural ventilation as per option two is a bad option, the proposal of decentralised mechanical extract ventilation in option one is “little better.”

Bootland criticised the lack of progress on current fabric standards, with only some very minor improvements to U-values based on the notional building compared to Part L 2021.

“We believe that there should be an option three in the consultation which allows better building fabric performance, to improve occupant comfort, reduce energy bills, and reduce demand on the grid during winter,” he said.

“We would propose that the passive house standard should be considered as option three and should be accepted as “Deemed to Satisfy” the Future Homes Standard.”

While applauding the decision to include heat pump-based heating in both options in the consultation as “an important step towards decarbonising our domestic heating supply,” Bootland warned that it was only part of the picture. “On its own, this move will not reduce energy bills or improve occupant comfort,” he said. “Whilst the heat pump may deliver some of the efficiencies, electricity is still around three times the cost of gas. Option two in the proposals would still have hot water and heating costs of £1,220 per year. Is this really the best that we can expect of a 'Future Home'?”

Bootland said the trust is “not convinced” by the proposed approach to deal with the performance gap within the standard. “If new homes are not certain to achieve the expected

levels of energy efficiency, and could require between 40 and 200 per cent more energy for heating than expected, then there could easily be examples of 'Future Homes' that are cold, costly to heat, and detrimental to the health of the inhabitants.”

The trust called on the UK government to follow Scotland’s lead and develop a passive house equivalent under building regulations.

“This would ensure that homes are warm in winter, cool in summer, have fresh indoor air and low heating bills. Surely that is the minimum we should expect from a 'Future Home'?"

In January, the Passivhaus Trust will be releasing further modelling and analysis comparing the energy performance of the Future Homes standard contenders with the passive house standard.

Simon McWhirter noted the timing of the government announcement, at a sensitive stage in the COP 28 climate summit. “On the last day of the global climate negotiations when we’re in the last chance saloon to keep temperatures under 1.5 degrees, it’s unconscionable that the government is consulting on scrapping the expectation that new roofs should have solar panels, when this is already widely delivered through current regulations.

“While the Government is right, of course, to finally end the era of burning gas and oil in our new homes and buildings, fitting low carbon heating sources such as heat pumps is already commonplace, and the standard provides no improvement in energy efficiency.

“We’re disappointed that, despite such a long delay in producing this draft standard, the Government still hasn’t included measures to reduce the embodied carbon emissions from construction which accounts for around 1 in 10 tonnes of climate emissions in the UK. Nor has it moved to tackle flood risk or end the huge water waste from new builds that is driving shortages and so much ecological damage.”

To respond to the consultation on the proposed Future Homes and Buildings standards, which ends on 6 March, visit tinyurl.com/FutureHomesConsultation. •

PASSIVE HOUSE+

NEWS

Free programme to bring passive house to UK architecture students A

new free-to-access training programme, Design Performance for Climate Action, provides architecture students across the UK with a solid foundation in climate-responsive building design – with passive house at its core.

Developed collaboratively by experienced passive house training provider Coaction Training CIC and the Passivhaus Trust, alongside RIBA, the Standing Conference of Schools of Architecture (SCOSA), and the International Passive House Association (iPHA), this partnership has been formed so that together the organisations can do more, reach more people, and have more impact.

Design is the most powerful tool we have to improve the energy performance of buildings, both upfront and in use. This new course empowers architecture students with the knowledge and skills to design high-performance buildings, using the passive house standard as a proven and quality-assured route to achieving good building performance.

“This course is responding to a direct demand from industry for more climate conscious architects,” said Passivhaus Trust research and policy director Sarah Lewis.

“We are excited to be upscaling passive house education in universities so that when architecture students graduate, they hit the ground running, embedding these skills in the practices where they work to have an immediate impact on the delivery of sustainable buildings in the UK.” Buildings are a significant culprit of carbon emissions – accountable for 35 per cent of total global energy consumption.

Passive house is a proven approach to reducing building energy use in addition to delivering high standards for comfort and occupant health.

The passive house standard adopts a whole-building approach focused on high-quality construction with clear, measured targets and certification through an exacting quality assurance process. The programme, ‘Design Performance for Climate Action,’ is tailored to support existing architecture teaching in the UK architecture schools. It addresses priority areas in the emerging RIBA climate knowledge literacy schedule and the ARB competencies that form the backbone of the curriculum.

“This is a huge opportunity for architects at the very start of their practice to gain ac-

Photo: BE-ST

(above) Coaction and BE-ST delivering passive house training.

cess to Coaction’s community of trainers - each bringing their long-standing experience and expertise within the passive house industry,” said Coaction director Sally Godber, who is also a director of leading passive house certifiers WARM. The course has been developed by a specialist team of low-energy experts and educators from Coaction Training CIC and the Passivhaus Trust, and critically examines the passive house standard, exploring its strengths and limitations over four modules, two of which cover the principles of building design for optimal performance, while the remaining two delve into the specifics of construction and services design.

“It is essential that all architecture students have access to tools that can support in their learning to develop sustainable approaches to designing buildings,” said Standing Conference of Schools of Architecture chair Prof Lorraine Farrelly. “This initiative, funded

by SCOSA and other partners will ensure our students can have an understanding of passive house principles to inform their approach to sustainable design.”

The course materials, which are available to all UK schools of architecture students

on an open-access basis, consist of online self-study modules. The partners’ ambition for the course is to expand opportunities for undergraduates and postgraduates in future years – including studio practice – empowering these students with tools and knowledge used in low-energy construction.

It is also hoped that the programme may be adapted and rolled out to other disciplines once successfully up and running.

Climate literacy among architects is fundamental to delivering a low carbon future and we are committed to ensuring that the next generation have the knowledge and skills they need. This important initiative will provide schools with resources to ensure that each and every architecture student enters the profession with a firm grounding in the principles of climate-responsive design.

We are looking for supporters to help us widen this programme further and empower the next generation of climate responsible architects to deliver a low carbon future. If you’re interested in being part of the change or want to find out more about the project, contact bex@coaction.org.uk or visit coaction.org.uk/blog/2023/design-performance-for-climate-action. •

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NEWS

PASSIVE HOUSE+

AECB conference 2023: from edible landscaping to whole life carbon

D

elegates at the 2023 AECB Conference heard a wide range of speakers covering everything from guerrilla edible planting to peak oil to detailed discussions on whole life carbon calculation.

The two-day event, held at the School of Natural Building at Tod College in Todmorden, West Yorkshire, started with an inspirational talk by community activist Mary Clear MBE on the work of Incredible Edibles. The local community benefit society that runs several initiatives to forge community within the town, centring on food, growing fruit, herbs and vegetables around the town – sometimes on an “ask forgiveness, not permission” basis, and runs weekly meals which are free to all.

The food theme was complemented by the plenary talk from Prof Steven N Newman of Biodiversity International, who spoke about food forests and new forest villages as a peaceful path to real reform.

AECB CEO Andy Simmonds updated delegates on the association’s work over the last 12 months, including the development of a step-by-step approach to retrofit under the CarbonLite Retrofit standard – an approach designed to enable significant decarbonisation of existing homes even when significant fabric upgrade measures are not possible.

Passive House Plus editor Jeff Colley

chaired the Sponsors Under Scrutiny session, where the AECB invited the event’s carefully selected sponsors to articulate their business in terms of specific sustainability concerns, with talks given by Platinum sponsor Partel’s director Hugh Whiriskey, and Gold sponsors including Medite Smartply’s head of technical affairs David Murray, Green Building Store MD Andy Mitchell, and Airflow Developments’ national business development manager Stephen Parker.

Day two opened with a plenary talk from broadcaster and architectural designer Charlie Luxton, who described how his firm’s projects approach sustainability, with an emphasis on passive house energy performance levels and a creative yet rigorous approach to a range of sustainability considerations including reducing embodied carbon, circularity and biodiversity.

Luxton’s talk was followed by a joint plenary by Prof Robert Lowe and Dr Lai Fong Chiu of UCL Energy Institute on systems shocks and peak oil, including the problem of negotiating multiple constraints on energy, economic and geopolitical development through the 21st century.

Over the two days a number of interactive, hands-on and technical workshops were hosted on a diverse range of subjects, with highlights including Dr Huda

(above) Charlie Luxton describing how the ratio between carbon emissions from operational energy use and embodied carbon can shift as low energy building efforts advance.

Elsherif and AECB CEO Andy Simmonds describing their work on creating climate resilient buildings in the global south; a panel discussion with QODA Consulting’s Dr Sarah Price, MCS Charitable Foundation’s Alastair Mumford, LEAP’s Mark Siddall and AECB standards manager Tim Martel on the CarbonLite Retrofit step-by-step standards; Greengauge’s Toby Cambray on deep home retrofit; and workshops by The School of Natural Building’s Barbara Jones on pre-fabricated straw panels and Partel’s Dara McGowan on airtightness application. •

ASBP Awards shortlist announced

T

he Alliance for Sustainable Building Products has announced the shortlist for its 2024 awards – including everything from biogenic passive houses to reclaimed steel and AIbased whole life carbon optimisation software.

The ASBP Awards 2024 will include awards under three categories: project, product and initiative. In each case the breadth of shortlisted projects is striking.

Since launching in 2018, the ASBP Awards have provided a platform for industry leaders, innovators and radical thinkers to highlight their exemplar building projects, problem solving products and transformative ideas. To date, over 60 applicants have been shortlisted, with 24 winners being awarded a coveted ASBP Award trophy for accelerating the pace of change in industry.

This year’s finalists will be invited to present at the Healthy Buildings Conference and Expo, which returns as an in-person event for the first time since 2020, on Thursday 29 February at the Building Centre in London.

The project category shortlist includes a project featured in this issue of Passive House Plus: Goldfinch Create and Play café, a passive house in Bristol built with a heavy emphasis on tim-

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ber and timber-based materials. Other finalists include the adaptive reuse of the Grade II listed East Ham Old Fire Station, and a combination of new build and sympathetically repurposed historic masonry transmitter buildings at Houlton Secondary School.

The shortlisted products include Clime Armourcoat’s cement-free clay lime plaster; Honext Board FR-B, which is made from 100 per cent upcycled waste fibres; the Natureplus-certified Keim Twinstar exterior masonry paint; Geosentinel’s water-saving Washbox closedloop, mobile wash station; EMR’s Reusable Steel, a reclaimed material designed with future circularity in mind; and Natural Building Systems’ breathable, modular building system.

The initiative category includes: • Qflow’s automated data collection and aggregation platform for construction projects • Preoptima’s AI-driven early-stage carbon optioneering software • Grosvenor and Heart of the City’s free supplier mentor programme for reducing emissions in the

property sector • The HTS Stockmatcher selection tool built to procure reclaimed steel for use in new construction projects • Gentian’s deep learning and AIbased approach to assessing and reporting on biodiversity value • The Reyooz circular economy software platform • SponsorConstruction4Refugees’ Renovate, Support, Empower, which focuses on providing sustainable housing and support for refugees by renovating abandoned buildings • The Environment Agency’s Pathfinder TEAM2100 Programme, which delivers flood risk management infrastructure by applying circular economy concepts • The MDFR Fibre Recovery Technology, which transforms post-use MDF into a valuable resource • NMITE’s groundbreaking Timber Technology Engineering and Design course. •

PASSIVE HOUSE+

NEWS

Scotland committed to continuing passive house journey

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atrick Harvie MSP, the Scottish government’s minister for zero carbon buildings, active travel and tenants' rights, was a keynote speaker at the UK Passivhaus Conference in Edinburgh on 17 October, and shared his vision for energy efficient and low carbon buildings in Scotland.

In January 2023, the Scottish government announced plans to introduce new minimum environmental design standards for all new build housing to meet a ‘Scottish equivalent’ to the passive house standard. Harvie gave an update on how the policy is developing.

A cross-industry working group is currently working through the policy details, with a thorough consultation on the proposals due to begin in 2024.

Minister Harvie said: “I am very pleased that Scotland is hosting this year’s conference, reflecting the leadership shown through our intent to introduce a Scottish equivalent of the passive house standard.

“Improving the energy performance of our new homes and buildings is essential to cut overall energy use and help end our reliance on fossil fuels, which exposes everyone to volatile prices.

“The passive house standard encourages the design and construction of low energy buildings, which complements commitments already made in the Bute House Agreement.

This is about delivering high quality, low en-

ergy and healthy buildings for people to live in that are built to the standards to which they are designed.”

Passivhaus Trust research and policy director Sarah Lewis commented: "Scotland is leading the way in the UK – and the world - with its commitment to delivering comfortable, affordable and low carbon housing.

Building on the Scottish government’s leadership, our conference has explored the practical and policy aspects of scaling up a passive house equivalent standard in Scotland, with discussions on standards, tools, certification, and expanding passive house training and the supply chain."

The conference showcased passive house projects across Scotland, from Fife Council’s super-sized 23,000 m2 Dunfermline Learning Campus to Midlothian Council’s ambitious social housing programme delivering over 200 passive house council homes. The conference also featured Scotland’s first passive house school – Riverside Primary School for Perth and Kinross Council – and the City of Edinburgh Council’s passive house schools’ programme. It is estimated that there are 35 passive house schools currently underway or in the pipeline in Scotland.

Sarah Lewis said: “An innovative funding mechanism from the Scottish Futures Trust has encouraged the building of schools to the passive house standard in Scotland. Projects

(above) Scotland’s zero carbon buildings minister Patrick Harvie gave the keynote speech at the UK Passivhaus Conference 2023.

receiving funding need to meet a very clear energy target and funding may be reduced based on any performance gap post-completion. The passive house standard effectively eliminates the performance gap, de-risking the securing of funding. It has been impressive how swiftly the industry, supply chain and clients have adjusted to delivering to the passive house standard in the education sector.”

More Scottish passive house projects are showcased at: ukphc.org.uk/scottish-showcase.

The Passivhaus Trust is actively engaging with the Scottish construction industry to help it scale up to deliver the Scottish government's ambition for a Scottish equivalent to the passive house standard.

Free resources, training, and guidance are available at www.passivhaustrust.org.uk. •

Green finance for green homes must meet new rules, experts warn

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reen home certifications and mortgage products in the EU must align with new EU rules on green finance, the pan-European Smarter Finance for EU consortium has warned.

In 2022, the EU passed into law the EU taxonomy for sustainable activities, a landmark policy which is rapidly moving the finance industry towards quantifying and reducing environmental impacts of economic activities. As real estate and construction are downstream of finance, the taxonomy has serious ramifications for these sectors too.

While the UK government has repealed the EU taxonomy under the Financial Services and Markets Bill, and is working on establishing a UK taxonomy, the international nature of the finance industry means that the requirements of the EU taxonomy may gain currency in the UK. The taxonomy is a classification system established to clarify which economic activities are environmentally sustainable, in the context of the €1 trillion-funded European Green Deal and its targets to cut net green-

house gas emissions by at least 55 per cent from 1990 levels by 2030.

Smarter Finance for EU spokesperson and Passive House Plus editor Jeff Colley said: "In the absence of sufficiently tight rules and definitions to define greenness, it has been possible for lenders to develop ostensibly "green" property finance products which may lack rigour and focus only on one sustainability feature, such as energy performance. That won't wash any more, because of the EU taxonomy."

Supported by the EU Life programme, Smarter Finance for EU has been established to facilitate the uptake of two key building blocks for decarbonising buildings: credible, evidence-based green home certifications, and tailored green finance products such as mortgages, loans and development finance. The project is essentially the second phase in the broader Smarter initiative, which has a global remit. From a standing start the first phase, Smarter Finance for Families, led to €8.5bn worth of investments in certified green homes, and

the development of 13 green mortgage and development finance products.

The Smarter Finance for EU consortium's implementing partners include green building councils and energy agencies who are defining or finessing green home certification systems to ensure taxonomy alignment.

The consortium is also developing plans to establish a European Centre of Excellence to serve new and existing implementing partners from across Europe.

Co-ordinated by the Romania Green Building Council, the partners in Smarter Finance for EU include the Irish Green Building Council, Luxembourg-based sustainable finance facilitator EnerSave Capital, Passive House Plus publishers Temple Media Ltd, the association Energy Efficient Cities of Ukraine, Green Building Council España, Portuguese energy agency Adene, Habitat for Humanity International, and the European-Ukrainian Energy Agency.

For further information visit smarterfinance4.eu •

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DR MARC Ó RIAIN

COLUMN

Bedding sustainability into British buildings: Bioregional’s BedZed Shortlisted for the Stirling Prize in 2003, BedZed was a prominent example of architecture starting to pay attention to sustainability. But how well did it work? In the latest part of his series on the history of low energy architecture, Dr. Marc O Riain looks back at a landmark project.

I

n 2002, as governments across Europe started to integrate Kyoto protocol targets into building regulations, a medium sized mixed-use development outside London aspired to become a seminal low carbon super sustainable community.

BedZed tested a lot of sustainable concepts in a real world setting together with human behavioural change as a central focus. Some strategies worked better than others, but the scheme signposted the direction the rest of us had to take over the following 20 years.

The Beddington zero energy development was based in the London borough of Sutton, located close to a train line, including 100 homes, offices, a community centre, playing field, gardens and allotments. BedZed featured optimal southerly orientation for winter solar heat gain, a passive ventilation strategy, an aspect of heat exchange, double and triple glazed windows, southerly conservatories, super insulation, good airtightness, stack ventilation, plug load monitoring, photovoltaic panels and initially a combined heat and power-based district heating system. Many of the materials used in the construction of the buildings were reclaimed or sourced locally, thus reducing the embodied carbon by 20 per cent to 30 per cent.

The overall design resulted in a reported 90 per cent reduction in fixed loads, and a 56 per cent overall carbon reduction when compared to an average UK home, with all renewable energy accounting for 20 per cent of all site electrical demand. Note that at this time CHP was considered renewable, as the development intended to use reclaimed timber – which led to impurities impacting the performance of the CHP. The profile of the building is designed to

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minimise overshadowing to the southerly face of the block to its rear. Passive ventilation combined with thermally massive materials help to offset heating needs. Conservatory doors are intended to be opened during the summer to allow for trapped heat to dissipate out, and prevent overheating, and in the winter internal doors with stack ventilation are intended to draw solar heat gain from the conservatory through the building. The CHP plant was less successful due to maintenance issues and as a result the company ceasing trading. The 2007 building occupancy survey showed that 56 per cent of occupants surveyed complained about overheating during the summer period. Research indicated that poor user education on the design principles of the houses and user behaviour mitigated against passive solar heat in winter and aggravated heat demand in the heating season. Looking forward 20 years from 2002, some of the learning outcomes might include the use of a mechanical ventilation heat recovery system combined with an air source heat pump as less complicated solutions to District CHP and natural ventilation, especially where we have better airtightness and control.

Other aspects of the sustainable design strategy included one car parking place per home, car sharing, free electric car charging with good links to public transport, and bicycle storage on site. This resulted in an average resident’s mileage of 3,138 per person, which would be 64 per cent lower than the average local area resident. While this is good, BedZed residents were three times more likely to fly abroad than local residents, mitigating against carbon offsetting targets.

The development also used a sustainable urban drainage system (SuDS), with permeable paving, green roofs, and a soak away ditch. Wastewater was treated with a mixture of biologically active sludge and reedbeds, an expensive system to run from an electrical standpoint. Rainfall collection is mixed with water to flush WCs, resulting in a 50 per cent lower use of water when compared to UK average.

Remotely located shared recycle bins are less successful because of distance and human behavioural issues. However, com-

munity composting, helped very much by peer education and chats with the neighbours, has been much more successful in local food gardens and allotments. Food is grown on site and accounts for an 8 per cent reduction in the total CO2 footprint.

The local organic vegetables are sold on Sunday and Monday markets helping to build an inter-reliant community. Interestingly, BedZed residents know 20 people in the development by name, which is double the strong community benchmark of 10, with one person being able to name 150 neighbours. This is a testament to the design of the project by Bio-Regional and ZED Factory with Tom Chance.

BedZed was indeed a ground-breaking project which field-tested a combination of design and sustainability strategies, sometimes illustrating limitations, but becoming very successful in reducing the carbon footprint of its residents. It faced problems such as overheating and having to switch from CHP to gas which undermined its sustainability targets. That said the rest of us learnt that we need to depend on more reliable renewable energy solutions that are less prone to variable behavioural conditions. Natural ventilation is more problematic in urban contexts where privacy and security are an issue, leading to windows being closed and curtains been placed over windows. Even 20 years on we have a lot to learn from BedZed, in designing for better communities and delivering real CO2 reductions in terms of build, operation and lifestyle.

Much of this article is drawn from data published in a paper written by Tom Chance in 2009, the BedZed monitoring report by Jessica Hodge and Julia Haltrecht for BioRegional in 2007, and the findings of a PhD thesis by Janet Young in 2015. n

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.

Photo: Tom Chance/BioRegional

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CASE STUDY

HANDLED WITH CARE EXETER EXTRA CARE SCHEME GOES PASSIVE TO PROTECT THE ELDERLY If thermal comfort is important for people of all ages, it’s even more so for elderly people, for whom the right living conditions can be a matter of life or death. Passive House Plus visited one award-winning extra care facility in Exeter to learn how the decision to go passive was working out for the residents.

Words: Kate de Selincourt Additional reporting: Jeff Colley

IN BRIEF House type: 4,457 m2 care home (53 one and two-bed apartments) Method: Cavity wall with precast inner leaf. Communal heating and centralised heat recovery ventilation, with dynamically modelled summer comfort.

Location: Exeter Standard: Passive house classic Heating costs: £11 to £15 per month (indicative space heating costs for a one-bed and two-bed apartment*) * see ‘In detail’ panel for more information.

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£11-15 per month

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CASE STUDY

It’s unbelievable. My mother’s only been here a few weeks and the change in her is incredible. This is a miracle place!

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s you arrive at the new Edwards Court Extra Care housing scheme in Exeter, the entrance is understated, austere even. Go through the doors though, and you enter a surprising, lovely space. The foyer is high and airy , with double-height glazing looking out onto a garden. Above, a gallery is set into a wall richly decorated with natural wood fluting. People are sitting chatting and playing scrabble, watching the world go by.

Beyond the entrance, the corridors are naturally lit, some with views over the gardens or towards the river. You pass through daylit corridors, some with views over the river Exe, and more attractive communal spaces, again decorated with an abundance of solid natural wood and colourful furnishings. The building is peaceful and fresh, and with a goldilocks sort of temperature: not too warm, not too cool, and perfectly even.

What is probably loveliest of all about this apartment building though is the fact that it is council-owned and run. It is not a high-

Photos: Architype

end, eye-wateringly-priced private sector facility. The residents, who are mainly over 55, with low to moderate care needs, pay ‘affordable rent’ to live there.

The quality of the building is really appreciated by residents – and by their families.

“When people come in it’s absolutely ‘wow!’” one resident told Passive House Plus. “When my sister-in-law and our niece came to stay, they were really surprised at how nice it is – they said ‘Ooh, it looks like a hotel!’”

Design for users Edwards Court is in many ways quite different from a hotel, however. Most hotels feature long, straight, gloomy corridors, some enhanced with a hint of stale carpet. Edwards Court has none of that.

A hotel is built for privacy – however, Edwards Court is very much built for community too. To this end it cleverly borrows from the towns and villages of the outside world.

You have the chance to be among people even when not actively seeking company, and you can see what’s going on and who is around. If you want to socialise, there are places to meet for chat or a coffee, or to eat together.

This connectedness is achieved by a porous layout. Window and galleries like the one above the entrance foyer give views down from corridors into communal spaces. On the roof is a cafe serving snacks and hot meals, and the popular roof terrace has views over the leafy riverside to the hills beyond.

Individual apartments can be fully private, or residents can peek out slantways from their kitchen windows down the corridor.

Once out of the door, each flat has a built in seat (that some residents have personalised with ornaments).

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The client team at Exeter – in particular, Exeter’s asset management lead Gary Stenning, and Emma Osmundsen, the then MD of Exeter City Living – visited similar facilities elsewhere to learn what residents did and didn’t like. Then working with Lee Fordham, Kirk Rushby and colleagues at Architype they developed this very effective design.

Residents are full of praise for the facility. As one resident, Adrian, explained: “Before, we were in a flat supposedly for over 55’s, but my wife has increasing mobility problems and early dementia, and she was really struggling, even with a stair lift. She was very low, feeling like her life was over.

“Here everything is level access and with her wheelchair she can get everywhere in the building, and go out. She is so much better here, she settled in really quickly.”

Adrian is active in the community that is forming here – with chat sessions, board games afternoons, plus a weekly music evening that he organises.

Visible, tangible luxury Adrian’s appreciation of the building is shared by his fellow residents, Claire Taylor, the housing manager says: “Everyone finds the building light, bright and decorated in a very pleasing manner. They love the terrace upstairs and the view.”

The generous design and quality finishes were not imposed by architects spending their client’s money unasked. The luxury was absolutely central to the brief. “Exeter were very keen to drive the quality so it was the same as a private sector facility,” architect Kirk Rushby explains. If anything, Edwards Court is not only as good as most private sector facilities: compared to those Passive

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House Plus has encountered, it is rather nicer.

In the individual flats, the thoughtful layout and beautiful finishes continue. The ceramic tiled floors give off a gentle, even heat in winter. Every flat is well daylit and has a balcony big enough to sit out on, plus room for some pots. The balconies are all angled to catch the sun for at least half the day.

But the luxury at Edwards Court is not only the things you can see, as the residents appreciate.

“The flat is really comfortable, we have thermostats to control the temperature, and can open the windows or the door to the balcony when it’s warm,” Adrian says. “We just wear short sleeves all year round, but it doesn’t seem to get too hot.”

He explained how his disabled wife has benefited: “We have underfloor heating which is great. My wife gets up often in the night, so it is lovely that it stays warm all night too.”

You could say the comfort in the building is distinguished by what you don’t notice: no cold or drafty places where you wouldn’t want to sit, no oppressive heat in summer – and no smells.

Even at lunchtime, the only noticeable smell is the faint linseed-y presence of the marmoleum underfoot in the circulation spaces.

“The air is always so fresh, you can’t smell any cooking, even from the café,” Adrian says.

Claire Taylor is experienced with care facilities and is used to residents being too cold or too hot. But not here: she has had not one complaint about indoor temperatures. “We have an age range from 50 to 101 and to never get, even in the depth of winter, any comments about the heating is

a major compliment.”

A safer environment As we know, the older we get, the more sensitive to cold (and excess heat) we become. For those of us with mobility or cognition problems – like many residents in Edwards Court – this vulnerability increases. As experienced passive house clients, Exeter City Council were well aware of the benefits passive house would bring to this occupant group.

The goldilocks conditions inside – not too warm, and not too cold – are not only very nice to live in: they keep the occupants safe, and aligned with the kinds of temperatures required by EN16798-1, a standard which sets indoor environmental quality requirements for energy calculation methodologies.

“We had in our minds that passive house would deliver thermal comfort and fresh air, with extraction where we need it. We are very pleased with the result,” Gary Stenning says.

The comfort makes life a great deal easier for the housing manager. “Age Concern recommends 21 C temperature for extra care provision,” says Claire Taylor. “People need to be warm, but if it is much warmer than 21 then you can start to risk issues with dehydration and stroke. We check the temperatures to make sure the flats don’t get too much warmer than this, and I haven’t seen any flats go above 21, winter or summer.”

Gary Stenning confirms this was the intention: “The hope was that in winter, with the warm surfaces including the windows, and lack of drafts, people would not feel the need to turn the heating up high. This seems to be what is happening.”

Older people are also more vulnerable to infections – not least, to airborne infections such as covid. Research has shown that the lower the air exchange rates in a building, the more outbreaks of respiratory infection you will have. The centralised passive house heat recovery ventilation here delivers a steady stream of pre-warmed air to a set target, without so much as a hum, never mind a draft. As Hugh Griffiths of E3 Consulting Engineers explains, the units chosen were from Swegon’s Gold range. “Plate Heat exchangers for the kitchen, rotary wheels for the general areas, chosen because they are passive house certified and because we have used them on previous passive house projects,” he says. While the systems have no recirculation outside of the air handling units themselves, in the case of the rotary wheels Griffiths says there can be a very small percentage of recirculation.

How the passive house standard was met Edwards Court contains 50 small flats, plus communal, office and circulation space, over four storeys. With a building this size, achieving passive house levels of thermal efficiency should not be challenging. The team opted for a layout with apartments on both sides of a central – albeit daylit – circulation spine.

This gives an excellent form factor (surface area to volume ratio) of 1.5. As a result Architype were able to specify a standard 150 mm cavity construction – cheaper and more straightforward than a thicker build-up.

The spec at Edwards Court includes a brick outer leaf, 150 mm cavity with Isover mineral wool fill and thermally broken TeploTie wall ties, albeit with a comparatively modest

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

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CASE STUDY

U-value for a passive house of 0.249 enabled by the building’s form factor, and the forgiving Exeter climate. Where most cavity walls have a masonry inner leaf the inner frame is pre-cast concrete, a decision that helped the building’s airtightness, albeit at an embodied carbon cost. Precast concrete tends to have high embodied carbon, given the typical spec of high cement content and steel reinforcement used for precast concrete. Early on, Architype explored the option of reducing the embodied carbon of the concrete via substituting cement for ground granulated blast-furnace slag (GGBS), a low carbon byproduct of the steel smelting process. “We started with a high GGBS specification for the concrete but this was removed due to the availability of GGBS due to high market demand,” says Kirk Rushby. “We were also therefore concerned about the actual sustainability of this.” The embodied carbon of the building wasn’t calculated, Rushby explains, because although Architype had helped develop Eccolab, a design tool which calculates embodied carbon, staff hadn’t been trained in the use of the tool when this project was at design stage.

To offer the depth of reveals needed for controlling summer solar gains, the windows and doors are not set in the line of the insulation, but rest on the inner concrete frame, with the insulation line kept continuous by the addition of a Compacfoam “frame round the frame” overlapping the cavity insulation.

“This was fiddlier to design, but actually, it was easier to build, as the weight of the doors and windows sits over the structure,” Kirk Rushby explained.

To avoid thermal bridging, balconies are self-supporting vertically, but still have to be tied in to the wall behind for horizontal stability. The ties had to be carefully designed to ensure there was no thermal bridge back into the building. And of course every balcony has a door, requiring a robust threshold (that can take feet and mobility aids).

As Kirk Rushby put it: “The inclusion of balconies immediately means 50 extra doorways. And you need to find a way to support them that does not form a thermal bridge. In passive house, balconies are a nuisance technically, but they were absolutely essential. The whole country learned this during lockdown – there was no question we would not include them. You can see from the way people use them that they are well worthwhile.

With such a good form factor, passive house heat demand could be met without the need for a south orientation. This was a great advantage, as to give equal access to sunshine for occupants on either side of the building, an east-west orientation worked a lot better – and fitted better with the shape of the site.

The alternative would have been two narrow wings of apartments, but this would have been an inefficient shape with a much bigger envelope, all needing a higher fabric specification, greatly pushing up the con-

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struction cost.

Of more concern perhaps was controlling overheating. “You do need to take care to control gains, with the lower morning and afternoon sun, so we paid a lot of attention to the glazing design. We were careful not to over-glaze, sizing the windows so they were well shaded by the reveals.

Chamfered inner reveals both increase the daylight indoors, and enable more effective ventilation even with window restrictors. The opening windows in the corridors are also useful in summer, Claire Taylor adds.

It was important to control internal gains from services – both to limit overheating, and to meet the passive house primary energy targets – not least because at the time of the design, back in 2017, the standard low cost choice for heating was gas. Gas has a high impact on the primary energy totals compared to heat pumps, in spite of the fact that gas has a lower primary energy score than grid electricity. The reason: fossil fuel boilers are less than 100 per cent efficient, whereas heat pumps are typically 300 per cent efficient or more.

Why was a fossil fuel source chosen for the project? “The project has been in the working for a long time and the design information for the project was being developed in 2015,” says Kirk Rushby. “At this time, we were encouraging clients to focus more on reducing demand rather than spending on any form of renewable. If we were to look at this today we would certainly take a different view, especially considering how appropriate a heat pump would be with a low temperature underfloor heating system.”

Communal hot water circulates at 60 C to avoid legionella risk to such a vulnerable population. But the circulation is confined to short loops that do not enter the apartments.

Separate small-bore spurs supply the shower, washbasin and kitchen to minimise losses into the occupied spaces. The communal underfloor heating circuit meanwhile runs at

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People need to be warm, but if it is much warmer than 21 then you can start to risk issues with dehydration and stroke. We check the temperatures, and I haven’t seen any flats go above 21, winter or summer

around 30 C, so again losses are very low.

Overheating risk was checked by IES dynamic thermal modelling as well as in PHPP. For a larger building, mechanical and electrical engineer Hugh Griffiths of E3 explains that dynamic modelling is recommended, to understand temperatures in individual spaces and across the day. Minimal overheating was predicted.

Following Exeter’s well-established requirements, indoor conditions were also modelled for predicted climate in 2050 and 2080.

This did point to a future overheating risk, so the building was future proofed accordingly. Rather than spend money adding shading and space cooling now, when it is not necessary, provision has been made to retrofit external shutters if and when the need arises.

Ventilation ducts were pre-insulated to allow for cooling, on the basis that taking down the ceilings to retrofit insulation later would be a horrible job.

Certification Mike Roe at Warm was the certifier, and found the project commendably straightforward to take through the requirements for passive house.

“It was not that different in the end from a standard apartment block. The differences were that the apartments are very small, so there is a high density in terms of equipment.

At that time PHPP was not as flexible about primary energy in relation to occupant density as it is now. The primary energy target was quite challenging to meet but we just got through, helped by the clever services design which really minimised the energy loads.

While the project may have navigated the rarefied space of passive house and PHPP calculation, how would it fare when put through the UK’s national methodology, SAP? Curiously, the apartments received relatively poor Energy Performance Certificate (EPC) scores of C and in once case B. Kirk

ph+ | edwards court case study | 27

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01250 872 261 01250 872 261 contact@proctorgroup.com 28 | passivehouseplus.co.uk | issue 46 contact@proctorgroup.com

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CASE STUDY

E DWA R D S CO U R T

Rushby says this is due to the way that EPCs are calculated. “Each apartment is assessed as a separate unit with a nominal U-value given to party walls. Essentially it doesn’t account for the efficiency of a large block of apartments huddled together.”

Passive house in Exeter Edwards Court is another fine feather in Exeter’s cap, adding to the already excellent reputation of passive house in the city. Adrian said his daughter uses the pool at St Sidwells, “which is also passive”.

“She finds it really nice at the leisure centre, and she said to us ‘if your new flat is passive it should be good’.”

The considerate management and care provisions, the occupant-centred layout, and the gorgeous fit-out of the building, combined with its unobtrusive comfort, have worked wonders for some occupants. The son of another resident told Passive House Plus that his mother’s wellbeing had transformed since she had moved in. “It’s unbelievable. She’s only been here a few weeks and the change in her is incredible. This is a miracle place!”

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REFERENCES

Cold Truths, Passive House Plus Issue 43.

Passive house Benefits: Health, Wellbeing & People Performance. www.passivhaustrust.org.uk

SELECTED PROJECT DETAILS

Client: Exeter City Council Architect: Architype Ltd M&E engineer: E3CE Civil/structural engineer: Price & Myers Energy consultant: Elemental Solutions Project management/quantity surveyors: Arcadis Main contractor: Kier Construction Ltd Mechanical and electrical contractor: Whitehead Passive house certifier: Warm Windows and doors: Ecowin Roof lights: Lamilux Entrance doors: Raico Wall insulation: Isover Thermally broken wall ties: Ancon Thermal blocks: Foamglas Roof insulation: Bauder Floor insulation: Foamglas Floor insulation: Styrene Airtightness products: Pro Clima Bricks: Ibstock Timber flooring: Junckers Floor tiles: British Ceramitile Linoleum: Forbo Mechanical ventilation supplier: Swegon

1 Installation of EPS insulation below slab; 2 Foamglas installation below structural walls; 3 tight insulation cut to soil stack penetration; 4 edge of ground slab revealed after formwork removed; 5 aerial shot of the precast concrete frame erection; 6 a dedicated mitre jig setup on site to cut EPS plinth insulation; 7 neat and tidy plinth insulation install to the building perimeter; 8 weathertight seal between windows and concrete frame; 9 quality control of the mineral wool cavity insulation with TeploTie basalt wall ties; 10 excellent weatherproofing around the penetrations for the air handling unit.

ph+ | edwards court case study | 29

E DWA R D S CO U R T

CASE STUDY

www.ecomerchant.co.uk www.ecomerchant.co.uk info@ecomerchant.co.uk info@ecomerchant.co.uk +44 (0) 1793 847 444 +44 (0) 1793 847 444

SUSTAINABLE SUSTAINABLE BUILDING BUILDING MATERIALS MATERIALS FROM FROM FOUNDATION FOUNDATION TO TO RIDGE RIDGE

WINNER OF THE SUSTAINABILITY PRIZE WINNER OF THE SUSTAINABILITY PRIZE

Creating quality low energy architecture requires a dedicated, Creating quality low energy architecture requires a dedicated, knowledgeable team from initial concept right through to finishing knowledgeable team from initial concept right through to finishing touches. Ecomerchant is a key part of that team for Charlie touches. Ecomerchant is a key part of that team for Charlie Luxton Design. Our values align, creating good buildings that Luxton Design. Our values align, creating good buildings that perform and last whilst respecting our environment. perform and last whilst respecting our environment.

Charlie Luxton Charlie Luxton Principal, Charlie Luxton Design Principal, Charlie Luxton Design Black Barn Studios by Black Barn Studios by Charlie Luxton Design Charlie Luxton Design Winner of Architects' Journal Winner of Architects' Journal Sustainability Prize 2023 30 | passivehouseplus.co.uk | issue 46 Sustainability Prize 2023

CASE STUDY

E DWA R D S CO U R T

IN DETAIL The UK’s first and only passive house extra care apartments. Exeter City Council’s innovative new Edwards Court Extra Care scheme provides 53 one and two-bedroom mixed tenure apartments. Designed to encourage community and companionship among its residents and neighbours, a variety of communal areas are interspersed throughout the building, on the rooftop, and in the garden walkways and terraces.

With in-depth research into dementia support and new design thinking, Architype has created a healthy, homely and sociable environment where residents can safely maintain an independent lifestyle with various levels of support and care.

Designed specifically to address the mental and physical needs of an older demographic, these welcoming ‘homes for life’ encourage movement and social inclusion, helping relieve demands on the NHS. To meet Exeter City Council’s demanding sustainability and health and wellbeing standards, the passive house design helps address fuel poverty by radically cutting heating bills and is climate-proofed to 2080.

Building type: A 4,457 m2 care home including 53 one and two-bedroom mixed tenure apartments.

Site type & location: Suburban brownfield site on the edge of Exeter City.

Completion date: September 2021 Budget: Final account figure approx £12m.

Passive house certification: Certified passive house classic Space heating demand: 13 kWh/m2/yr Heat load: 9 W/m2 Primary energy non-renewable: 133 kWh/m2/yr Heat loss form factor: 1.47 Overheating: IES modelling 0.5-1% using current weather data Number of occupants: 80 Airtightness (at 50 Pascals): 0.23 ACH Energy performance certificate (EPC): Each apartment has a separate figure but all apartments achieved a C rating between 76-79 with one exception of B (83) Embodied carbon: Embodied carbon analysis not undertaken Measured energy consumption: Not yet available

Thermal bridging: With a large building and therefore better form factor the attempt was to make the building form efficient enough that a typical insulation of 150 mm thick masonry cavity fill generally could be used that would be similar to a more standard construction.

Initially design loads allowed a raft slab on top of pile-caps by designing the structure to spread across load-bearing walls rather than having point loads. Additional loads from the precast frame manufacturer meant that this could not be achieved, but Foamglas could be used below walls to take the loads with an EPS infill which still made a thermally bridge-free construction.

Parapets were reduced to a minimum but required to terraces and plant areas. These were thermally broken with a break designed by the concrete frame subcontractor similar to a Schoeck type.

Balconies were kept structurally separate from the building with ties back to remove thermal bridges and lime mortar with bed joint reinforcement was used to allow the five storeys of brick to be self-supporting, thereby removing the need for structural shelf brackets.

Heating costs: Calculated costs for typical apartments of £11 to £15 per month, based on a 45 m2 one-bed apartment, and a 62 m2 two bed apartment. This is based on a number of assumptions. First, it’s assumed that each apartment has the same space heating demand (13kWh/m2/yr) of the whole building, when the reality is that some will be above or below this figure. Secondly, it’s assumed that that the boiler will be delivering heat in line with the stated gross seasonal efficiency of 96.5 per cent.

Thirdly, a high unit price for communal gas of 22p is assumed, based on an article from The Guardian on gas price spikes, “UK households with communal heating facing 350% rise in energy costs.” If we instead focus on the whole 4,457 m2 building, the calculated space heating total is £1,100/month – for 53 flats and all common areas.

Ground floor: 65 mm bonded screed with underfloor heating with VCL, on 25 mm rigid insulation, on 300 mm reinforced concrete slab, on 100 mm of EPS insulation with Foamglas in load bearing areas. Concrete slab acting as airtight layer. U-value: 0.206 W/m2K Walls: 100 mm brick tied back with TeploTie thermally broken wall ties, 150 mm full fill Isover CWS 34 glass mineral wool slabs, 200 mm precast concrete walls with service zone and plasterboard. Precast concrete with external joints

sealed with Pro Clima Aerosana Viscon liquid sealant. U-value: 0.249 W/m2K Roof: Bauder bituminous warm roof system with waterproof layer, 160 mm PIR insulation and VCL on 150 mm precast concrete planks. VCL acting as airtightness layer. U-value: 0.131 W/m2K Windows & external doors: Zylefenster windows

by Ecowin, triple glazed aluclad timber windows.

Average Uw-value: 0.84-0.88 Wm2K. G-value: 0.48 Roof windows: Lamilux FEEnergysave triple glazed roof lights Heating system: Two Potterton Sirius 3 90kW gas boilers with a gross seasonal efficiency of 96.5 per cent distributing through underfloor heating embedded in the screed.

Ventilation: Four centralised ventilation units, as follows: North flats and communal areas: Swegon Gold F RX (Size 14): Temp efficiency: 86 per cent South flats and communal areas: Swegon Gold F RX (Size 12) Top: Temp efficiency: 85 per cent Fourth floor communal areas: Swegon Gold F RX (Size 07): Temp efficiency: 84 per cent Kitchen: Swegon Gold F PX (Size 07): Temp efficiency: 76 per cent Water: Low flow fittings as per AECB Water Standards Electricity: No renewables on site Sustainable materials: A priority for Exeter City Council, the building aligns with the Building Biology Association’s 25 Guiding Principles of Building Biology for a healthy, beautiful and sustainable building in an ecologically sound and socially connected community.

It reduces physical, chemical and biological risks and eliminates toxic materials and electro-magnetic radiation. Materials are as natural as possible, with particular care made to avoid skin irritants and ensure optimum air quality. Paints are natural and timber is lacquered rather than oiled to reduce VOCs (Volatile Organic Compounds) which are hazardous to human health. To keep dust and particulate matter levels low, surfaces that more easily collect duct such as carpets have been avoided. Fibre insulation has been selected on the basis of having the lowest formaldehyde content possible.

Cellulose insulation to top floor terrace area.

Natural finishes such as oiled timber floors, linoleum, timber ceiling and wall finishes, low VOC paints and ceramic tiles.

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CASE STUDY

PLAY TO WIN CREATIVE PLAY CAFÉ BRINGS PASSIVE BENEFITS FOR BRISTOL FAMILIES A site with a dilapidated building in Bristol has been transformed into a crucial social space by a husband and wife team of environmentally and socially engaged architects, aided by a polymath sustainability consultant.

Words: Jason Walsh Additional reporting: Jeff Colley

32 | passivehouseplus.co.uk | issue 46

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IN BRIEF

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Living room Ensuite Stairs Bed 3 Bed 1 Storage Utility

Building type: 150 m2 mid terrace café and art studio Method: Timber frame, insulated foundations, cellulose, heat pump, PV Location: Bristol Standard: Passive house classic (pending) Embodied carbon: £75 / month* * Calculated total energy costs, including standing charges and feed-in tariff income. See ‘In detail’ panel for more information.

£75 per month

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CASE STUDY

hen Nicole Strong and Mark Finney arrived in Bristol they were seeking a change. They got one, and a challenge, too.

Coming from Cape Town, the couple, both of whom are architectural professionals, relocated to England, Finney’s home, and set to work. Arriving in the city, Strong, who had been a senior landscape architect for the city of Cape Town, decided to turn a problem into an opportunity: having young children, she found that the city, despite its reputation as one of England’s most vibrant, was missing something. But using her background as the foundation, she set about building it.

“My background is in architecture, urban design and city planning, and I am interested in the social side of buildings and the built environment,” she said.

So what was missing? Strong parlayed her experience to create a new space that offered families somewhere to be that was neither home nor an unsuitable commercial space.

“The coffee shops are very dark and dingy, and there are not many healthy options in terms of food. There are play centres but they can be a little bit overwhelming [both] for parents and children,” she said.

The end result is Goldfinch, a welcoming community space designed to give families the freedom to imagine, create and connect, beyond the confines of the traditional café or classroom.

“We wanted to create a space where children could be, where adults could be, where

34 | passivehouseplus.co.uk | issue 46

they could connect in a really beautiful space. So we found a building,” she said.

The building was far from suitable, however. The 80 m2 site, located in the Bristol suburb of Westbury-On-Trym, was home to a one-storey building in extremely bad condition that had previously housed a print shop.

Nevertheless, despite this and the bad luck of beginning the process just as the Covid-19 pandemic and its attendant lockdown shut down construction, Strong and Finney proceeded.

“It was a dilapidated building that needed to be completely rebuilt. Covid slowed things down, but we got the planning [permission],” she said.

Planning was approved for a two-storey – 75 m2 per storey – building to house the new venture.

Strong’s husband Finney, a partner in Seb + Fin Architects, took up duties as architect on the project and, despite the site’s suitability, it soon became clear that an entirely new building would need to be designed and built.

While Finney says he prefers to preserve building fabric when it is possible, his description of the existing building on the site makes it clear why the couple did not go down that road.

“We did look at a retrofit. It was a single storey, but increasingly dilapidated building and half of the site was a yard. Part of it had a corrugated tin roof, which was collapsing, the walls were collapsing and were covered in algae and mould, so we had to demolish

The walls were collapsing and covered in algae and mould, so we had to demolish and start again

and start again,” he said.

“The previous tenant moved out because the building was so dysfunctional. It was heated with electric bar heaters [and] frankly, it was getting dangerous”.

Sustainability consultants Ecospheric, who provided energy and life cycle assessment consultancy on the project, did attempt to see if a retrofit was possible, but the results were not positive.

“We looked at viability, but it was too restrictive,” said Kit Knowles, Ecospheric’s managing director. “First, as an infill site it was tight, as they always are, but the building was not really salvageable. It was a case of too structurally compromised, too much function required and too little space”.

Skills on site If the existing building was an inauspicious start the site at least afforded the oppor-

CASE STUDY

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GSPublisherVersion 560.0.93.26

GSPublisherVersion 560.0.93.26

We had already done all of the joinery and then the Russian invasion of Ukraine meant birch ply became much harder to get

tunity for a new beginning. As Seb + Fin Architects, a specialist in residential architecture, is enthusiastic about the passive house and Enerphit standards, building the new building to passive standard was the obvious choice.

Finney designed the building with the ground floor resting on a concrete raft foundation with a 25 mm thick concrete slab, housed in an Isoquick insulated foundation system. The walls are made with timber I-joists with cellulose fibre insulation and an external render. “Internally, on the walls, we get good airtightness,” said Finney.

Ecospheric, in its consulting role, took major steps to ensure that the building would meet passive house standards despite the difficulty doing so given its use as a café. Knowles and his colleagues did a feasibility study to establish how the passive house standard could be met for a building with this intended use, given the specific kinds of loads a café would bring. According to Knowles, other similar UK projects were thin on the ground at best. “There are cafés inside a university and a student accommodation unit, but those are much bigger, commercial buildings. So, this is the first time that’s been done in the UK.” This points to a general truism: while residential buildings tend to have very similar energy use profiles, non-domestic buildings are far

more varied, given the broad ranges of uses they encompass, and the consequent divergence in terms of impact on energy use. For a building where the main function is a café, a substantial amount of appliance use in a relatively small building pushes up the plug loads, and therefore makes it more challenging to meet the primary energy targets for passive house. “We did our modelling and consulted with the passive house certifiers [PH Certification],” said Knowles. “The conclusion is that it would be possible if we drew up a new profile with the Passive House Institute.”

Ecospheric also performed a whole life carbon analysis, a process analysis and engaged with the design of the mechanical and electrical systems.

“Carbon analysis was done with the creation of an ‘optioneering’ engine, looking at the viability and impact on a whole life basis, of both the active and passive elements.

Once we’ve got through that we know all of the different materials and methodologies we’re using and all the mechanical and elec-

Photos: Zed Photography / SuperFunkyPenguin Photography

trical elements. After that, we need to know how it is going to fit together: it’s the nitty gritty that gets it right,” Knowles said.

“Next, we used our detailing methodology process, called the ‘thirteen hats’. It’s an analysis where you put on a different hat and use that to guide our detailing process. Finally, we did the mechanical and electrical, getting involved with designing that,” he said.

Construction was contracted to Earthwise Construction, a Bristol-based specialist in passive house construction and heat recovery ventilation.

Both Strong and Finney complimented Earthwise’s work, noting that few contractors have the right skills and experience – and some of the few that do only work on massive projects.

According to Strong, working with Earthwise was particularly reassuring because previous experiences with other builders had not always been ideal.

“Because of our specialist contractor it went as smoothly as it possibly could. When we first tried out [passive house techniques]

ph+ | goldfinch create & play case study | 35

G O L D F I N C H C R E AT E & P L AY

CASE STUDY

at our home, with different contactors, there were some problems, Earthwise knew what they were doing,” said Strong.

Finney says he was glad to work with Earthwise because there are few enough contractors in the area with the right expertise.

“In Bristol, you’ve got a little group of about three people who can do this. One of them, I don’t think they touch things under half a million and are looking for more than a million: high-end houses, basically,” he said.

Earthwise was also able to make suggestions during the design and build, including how to meet requirements around heating and ventilation.

“We were very nervous about meeting building regulations requirements, but the contractor suggested using two residential MVHR units,” said Finney.

“We were incredibly pleased with the contractor because they were very experienced.

They were good at what they do, and so there was no need for hand-holding,” he said.

This was also important because one of the core dreams was for a healthy building for the families visiting for classes and social space at Goldfinch.

“Apart from sustainability, we wanted a healthy environment with good air circulation,” Strong said.

In addition to construction and ventilation, Earthwise also did all of the internal joinery.

“That was quite novel, [and was possible] because they are joiners,” said Finney.

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As it is not a residential building, however, there were additional challenges. As a result, the fact that a new build was required had some significant design benefits.

“Due to the high occupancy, the ventilation rate has got to be really high and that’s quite challenging to address, but the envelope is new so it was easier to achieve. Working around things in Enerphit is tricky: you always have cold bridges to address, whereas we just designed them out of it,” said Finney.

A Stiebel Eltron air source heat pump – selected by Ecospheric to ensure a low global warming potential refrigerant as part of the

performance spec – provides heating and cooling, while photovoltaic panels feed electricity to a battery for storage and later use.

Geopolitical events also had an impact, primarily on cost: both the post-pandemic supply chain crunch and the Russian invasion of Ukraine were felt.

“We were quite fortunate because the plot was purchased and was going through the legal side during lockdown. What we did suffer from was price inflation. We were relying on a lot of timber products, which all went up by 50 per cent. That has now levelled off but not come down,” said Finney.

CASE STUDY

“We had already done all of the joinery specifications and design and then the Russian invasion of Ukraine meant birch ply became much harder to get,” he said. Nevertheless, the project was completed and signs of success are visible.

“Because it’s tight and well-insulated we were able to do all of the hot water, heating and cooling from an air source heat pump on the roof and that’s distributed by the

ventilation system. The heat demand should be pretty low – it’s designed to minimise the demand,” he said.

Open for around three months at the time of publication, the next step for Goldfinch is to see if the building performs as expected.

“What we are keen to do is see how it works down the road,” said Finney.

“What we often tell clients is that if you did passive house modelling it should be

G O L D F I N C H C R E AT E & P L AY

pretty accurate – but we want to see just how accurate,” he said.

Of particular interest to Finney is understanding the impact of materials such as concrete and expanded polystyrene, choices forced on the design by the site.

“We’re very keen on embodied carbon analysis. We were keen to use as much timber and [as many] natural materials as possible, but in this case we had to use EPS and concrete and

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1, 2 & 3 The existing building was in extremely bad condition and structurally compromised; 4 work underway demolishing the building as it had to be completely rebuilt; 5 & 6 ground floor build-up features a 250 mm deep concrete raft slab with Isoquick 100 mm perimeter insulation upstand; 7 arrival of windows for installation; 8 timber frame structure progressing; 9 Smartply Propassiv OSB, seams fully taped with Pro Clima Tescon Vana; 10 Intello Plus membrane and ductwork for MVHR systems; 11 the Velux roof windows help to bring in more natural light; 12 installation of two 12.5 mm layers of British Gypsum FireLine board on timber battens.

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CASE STUDY

G O L D F I N C H C R E AT E & P L AY

[petrochemical-based] roof insulation. We would have avoided that on a greenfield site.

Also, there was zero information on the steel and that means we have to assume the worst case scenario and that could knock us out of the top bracket,” he said.

The experience, largely positive but not without the unexpected problem of inflation in the price of materials, has only confirmed Finney’s view that all construction projects should be sustainable.

“The government needs to come to the party and incentivise good building practice.

It should always be the case that choosing the green option is cheaper,” he said.

Embodied carbon Ecospheric’s carbon analysis included a life cycle assessment on the building calculated using OneClickLCA. The building was assessed against the RIBA 2030 Climate Challenge, and compared against the RIBA 2030 target for schools, as the closest building use category to the play cafe. The building met the RIBA 2030 target of 540 kg CO2e/m2 GIA, covering the RICS life cycle stages A1 through C5, but excluding operational energy and water use (B6 & B7).

The reality however may be better still.

One problem Ecospheric encountered was the absence of Environmental Product Declarations for big ticket items such as the steel, concrete and rebar. “We have assumed average UK figures, to be conservative,” said Knowles.

Life cycle assessments cover up to four modules: A, B, C and D. Module A covers the carbon emitted in manufacturing the building’s materials and technologies, in transporting them to site, and in the construction process itself. B covers emissions during the expected lifespan of the building – in the UK a reference life of 60 years is typically taken - including maintaining, repairing or replacing materials, and operational energy and water use. C covers the building’s end of life, including emissions released by the building being knocked down (or hopefully taken apart), including material disposal. D focuses on potential future uses of materials from the building in other applications. Module D

emissions typically aren’t included in embodied carbon targets, but it’s encouraged to report them separately. Frankly, once a life cycle assessment moves beyond module A, the figures start to become heavily reliant on assumptions – about how long a component will last, about how a building will be maintained, about how polluting the manufacture of replacement components will be, and about how much care will be taken in deconstructing rather than just demolishing a building. While it is important to look at a building on a cradle-to-grave basis – and to think about designing the building in such a way as to minimise emissions down the line – Knowles makes the point that a particular focus on upfront emissions is key.

“We feel it is important to list the A1A5 figures separately as the next eight years are crucial for climate change,” he says, “and trying to predict what the embodied carbon of replacement materials in 30 years time or the end of life carbon in 60 years is pretty difficult.”

In this building, Ecospheric calculated a module A total of 353 kg CO2e/m2 GIA. If the CO2 stored in biogenic materials such as timber, wood products and cellulose is factored in, that total drops to 190 kg CO2e/m2 though LCA experts tend to counsel against netting off in this case, preferring instead to say that the upfront total is 353 kg CO2e/m2, with a further 163 kg CO2e/m2 stored in the biogenic materials in the building.

SELECTED PROJECT DETAILS

Client: Goldfinch Create and Play Architect: Seb + Fin Architects Civil / structural engineer: Build Collective Energy consultant and life cycle assessment consultant: Ecospheric Main contractor: Earthwise Construction Electrical contractor: Electrotech SW Ltd Airtightness tester/consultant: Building Analysis and Testing Ltd Passive house certifier: Zero Energy Build system supplier: Pasquill Cellulose insulation: Warmcel, via PYC Wood fibre insulation: Pavatex, via Soprema Floor insulation: Isoquick Airtight OSB: Medite Smartply Airtight membrane and tapes: Pro Clima via Ecological Building Systems Windows and doors: Viking Roof lights: Velux Entrance doors: Velfac Flooring: Forbo Roofing: Alwitra Evalon Rainwater systems: Lindab Heat pump: Stiebel Eltron, via Green Flare Mechanical ventilation system: Zehnder, via Earthwise Construction Photovoltaic supplier: JA Solar array and Pylontech battery, via Green Flare Sanitaryware: Ideal Standard

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A low-carbon building solution A low-carbon building solution for Passive House walls and roofs for Passive House walls and roofs

Suitable for new buildings with timber framing, Passive EcoWall provides a complete low-energy, diffusion-open design based on tried and tested Passive House principles.

Suitable for new buildings with timber framing, Passive EcoWall provides a complete low-energy, diffusion-open design based on tried and tested Passive House principles.

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Gutex Thermoflex Flexible wood fibre Gutex Thermofl ex insulation mat

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40 | passivehouseplus.co.uk | issue 46

Discover our solutions online at ecologicalbuildingsystems.com

CASE STUDY

G O L D F I N C H C R E AT E & P L AY

IN DETAIL Building type: 150 m2, mid-terrace two-storey timber frame café and art studio.

Site type & location: Suburban high street, Westbury-on-Trym, Bristol Completion date: July 2023 Budget: Construction cost including fit out and furnishings of £670,000 (excluding site purchase and professional fees).

Passive house certification: Passive house classic (certification pending) Space heating demand: 3.0 kWh/m2/yr Heat load: 6.7 W/m2 Primary energy non-renewable: 195.1 kWh/m2/yr Primary energy renewable: 77.5 kWh/m2/yr Heat loss form factor: 2.9 Overheating: 0.0 per cent of year above 25 C, assessed in PHPP Number of occupants: Ground floor max: 26 people (20 seated, 2 staff, 4 people queuing for take away).

First floor max: 26 people (12 children, 12 accompanying adults, 2 staff). A realistic average occupancy would be 20-40 people during daytime.

Airtightness (at 50 Pascals): 0.43 m3/hr/m2 at 50 Pa / 0.40 air changes per hour Embodied carbon: 540 kg CO2e/m2 GIA for RICS life cycle stages A1 through C5, but excluding operational energy and water use (B6 & B7).

Calculated using OneClickLCA. A1-A5 (cradle to practical completion) = 353 kg CO2e/m2 GIA excluding biogenic storage.

A1-A5 (cradle to practical completion) = 190 kg CO2e/m2 GIA including biogenic storage.

Measured energy consumption: Not available Thermal bridging: Continuous tongue and groove wood fibre to each façade; Isoquick below slab insulation with insulated upstands; Insulated reveal liners (wood fibre for main windows, spacetherm for roof light windows); Warm roof deck extending close to the perimeter, with insulated timber ladder structure to form perimeter edge. Building Y-value: 0.005 w/m2K, based on calculated thermal bridges.

Energy bills (measured or estimated): Estimate based on PHPP data and assumed levels of occupancy is £900/yr electricity based on current typical business energy costs of 30p/kWh and assuming 80 per cent self-consumption of energy generated by PV on roof, plus a standing charge of £200/yr. Export of the remaining 20 per cent is estimated to generate £200 in income at 15p/kWh. Ground floor: (Top to bottom) Marmoleum Cocoa - Earl Grey Chocolate finish; latex self-levelling compound; 250 mm deep concrete raft slab to structural engineer’s spec and detail; Isoquick 100 mm perimeter insulation upstand (vertically around perimeter of the slab), with the top of the insulation

level with the top of the floor screed; Isoquick 150 mm grade EPS300; Visqueen Radon R400 membrane with fully taped seams; non-shrinkable compacted fill; ground. U-value: 0.207 W/m2K. Walls: (Inside to out) Paint; two 12.5 mm layers of British Gypsum FireLine board and 3 mm skim coat plaster finish with all joints taped with scrim tape; 25x50 mm treated FSC certified pine battens, running vertically at 400 mm centres to form services void; 12.5 mm layer of Smartply airtight board with fully taped seams with Pro Clima Tescon Vana; 300x90 mm JJ I-joist construction fully filled with Warmcel cellulose fibre insulation; 40 mm Pavatex Isolair wood fibre insulation board mechanically fixed to the timber frame; Baumit render system including 2 mm Baumit SilikonTop finish render, Baumit premium Primer, 6 mm Baumit MC55 lime contact mortar, incorporating Baumit StarTex mesh. Colour Baumit W1208 ceramic white.

U-Value: 0.115 W/m2K. Where the external wall runs along the external maintenance access, the render system is replaced as follows to allow for pre-fabrication of wall panels: 40 mm Pavatex Isolair wood fibre insulation board mechanically fixed to the timber frame; Pro Clima Solitex Frontra WA breather membrane, with fully taped seams using Tescon Vana; treated 44x44 mm pine battens running vertically at 400 mm centres (and doubled up at junctions of boards) with Tenmat FF102/50 ventilated cavity barrier; 3050x1200x8 mm RockPanel. Panels screwed into battens with stainless steel screws. The top of the panels are weatherproofed with a PPC aluminium sill (colour matched to windows external colour) fixed to the I-joist beyond. The underside of the panels includes a stainless steel insect mesh to form a continuous barrier to vermin and insects.

The wall plinth (dense blockwork upstand with Isoquick insulated upstand externally) clad with 15 mm Wetherby Brick Slip Cladding System in ‘Staffordshire Blue’ colour. U-value: 0.115 W/m2K. New party walls: (Inside to outside) Paint; two 12.5 mm layers of British Gypsum FireLine board and 3 mm skim coat plaster finish with all joints taped with scrim tape; 25x50 mm treated pine battens, FSC certified, running vertically at 400 mm centres to form services void; 12.5 mm layer of Smartply airtight board with fully taped seams; 300x90 mm JJ I-joist construction to structural engineer’s spec fully filled with Warmcel cellulose insulation; egg crate tanking system: Delta MS500 (8 mm cavity drain membrane) with fully taped seams and plugs to manufacturers spec. Minimum embedment of plugs in party wall to manufacturers spec. subject to party wall agreement; Koster Polysil TG500 (anti lime coating) applied to existing wall; existing masonry party wall; neighbouring building.

U-value: 0.121 W/m2K Roof: (Outside to inside) Warm roofing system

including Alwitra Evalon in slate grey (RAL 7015) with colour matched 75 mm drip trims; 200 mm (100+100 mm) PIR with staggered board application, secured using manufacturer approved, thermally broken fasteners; InStar Elotene DSN self-adhesive total vapour barrier; 18 mm OSB3 T&G board fixed to timber structure below; firring timbers: ex 47x225 mm C24 timber at 400 mm centres at minimum 1:60 falls. Timbers trimmed to a minimum of 70 mm; 300x90 mm JJ I-joist construction to structural engineer’s specification / specialist sub-consultants design to form a level ceiling; timber battens to form service void and allow ceiling to extend into window reveal; two 12.5 mm layers of British Gypsum FireLine board and 3 mm skim coat plaster finish with all joints taped with scrim tape; paint; acoustic panels. U-Value: 0.105 W/m2K Windows & external doors: Main entrance door: Velfac Ribo door and top light window triple glazed aluminium clad timber framed window and door, with Argon filling and overall Uw value of 0.89 W/m2K installed.

Windows and fire escape door: Viking triple glazed aluminium clad timber framed windows, with Argon filling and overall Uw value range between 0.74 and 1.4 W/m2K. The lower Uw value is due to fire-rated glass requirement.

Service access door: Moralt Ferro Passiv Firesafe FD30 Exterior MDF faced door with laminated pine frame (no glazing). Ud value of 1.0 W/m2K. PHI certified.

Roof windows: Two Velux UK08 triple glazed ‘Extra Heat’ roof lights with Velux UK08.

U-value: 1.01 W/m2K installed.

Heating system: Stiebel Eltron WPL-A 07 HK Premium Pack consisting of an air-to-water heat pump with cooling capacity, integral hot water cylinder with a nominal capacity of 168 L, and a 100 L buffer cylinder. The heat pump refrigerant R454C, has a global warming potential of 146.

Heating and cooling distributed via two Zehnder ComfoPost air-to-water heat exchangers (one per floor).

Ventilation: Two Zehnder Comfoair Q600 MVHR systems (one per floor). PHI certified. Heat recovery rate of 87 per cent thermal efficiency according to EPN standard 97.6 per cent.

Water: Low flush WCs and microbore hot water pipes.

Electricity: PV: 21 x JA solar panels JAM60S21-370/MR 370 Watts Inverter: S5-GR3P8K SOLIS - Ningbo Ginlong Technologies 8.000 kW Battery: PylonTech FORCE H2 7.1 kWh Sustainable materials: Timber frame using FSC certified timber and I-joists, cellulose insulation, wood fibre insulation and marmoleum floor finish.

ph+ | goldfinch create & play case study | 41

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CASE STUDY

IN BRIEF Building type: Retrofit and extension to 188 m2 bungalow Method: Bone-deep retrofit - floors dug out, chimney removed, roof replaced. Warm roof, external insulation, heat pump, MVHR Location: Monaghan Standard: Passive house classic

£43

Heating cost: €80/month* * All energy costs – including heating, hot water, lighting and plug loads.

per month 42

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€80 per month

BUNGALOW BILLS MONAGHAN RETROFIT TAKES PASSIVE ROUTE TO LOW COSTS AND HIGH COMFORT What does it feel like to suffer the cold, mould and discomfort of a 1960s bungalow, and experience its rebirth as a passive house? The owner of one award-winning project spills the beans.

by John Hearne Additional reporting by Jeff Colley

42 | passivehouseplus.co.uk | issue 46

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BUNGALOW BILLS

In the old house when you got out of the bed you would have [had to] hop, skip and jump to the bathroom because it was so uncomfortable.

Now when you put your foot onto the tile it isn’t cold. The underfloor heating hasn’t been on yet

I

t’s now fifty-two years since Jack Fitzsimmons’ highly influential book of house plans ‘Bungalow Bliss’ was first unleashed on the Irish market. Reprinted ten times, it sold in excess of 250,000 copies, and bears much of the responsibility for the fact that 15 per cent of all homes in the country are bungalows. The Sustainable Energy Authority of Ireland estimates that there are 300,000 dotted throughout the Irish countryside, 80 per cent of which have BERs of low D or worse.

Addressing their energy and comfort shortcomings has of course become one of the many building stock challenges we face.

Barry McCarron has answered these challenges brilliantly in the deep retrofit of his family home in Ballinode, Co. Monaghan.

He monitored the energy performance of the bungalow for two years prior to beginning the project. The costs came in at €3,711 in 2020/2021 and €4,773 in 2021/2022 – an average of €4,242 per year, excluding standing charges. One passive retrofit later and predicted annual running costs have dropped

to €1,082, again excluding standing charges, nearly four times cheaper. The total savings over the life of the mortgage as a result of the project come to €91,627, while the payback period for the additional cost of achieving the full passive house standard is just four years.

‘There’s absolutely no regret,” says McCarron, ‘I believe we’ve made a great investment in our family for the years ahead.’

Though this was his first passive project, Barry McCarron isn’t exactly a stranger to sustainable building. He is the current chair of the Passive House Association of Ireland, is head of business development with South West College, and for the past eight years has been teaching on their passive house designer course. Earlier in his career, he also put in what he describes as three ‘very very educational years’ doing BERs. His first passive project was always going to be worth checking out.

McCarron says that he and his wife Aisling had always expected that they would build a house on the family farm in Ballinode. Then,

in the lean years following the property crash, a bungalow opposite the farm came up for sale. They got it for just €95,000.

‘We lived in it for eight years,’ he explains, ‘but we didn’t really commit to the house. We only did superficial refurb work. We thought we would probably sell it and build new, but the longer we stayed without building, the more a new build came off the agenda and retrofitting came on.’

Wouldn’t it have been easier to just demolish and start fresh?

Maybe it would, says McCarron. ‘But I would have had to apply for full planning permission, which I probably would have got, but with the retrofit, I only had to apply for an extension, and it also avoided the necessity for an assigned certifier and all that comes with new build.’

The big attraction of retrofit however was that it was an opportunity to do something interesting and relevant. ‘I work in a college, and that keeps me away from real life, I’m always on the fringe of projects. This was an op-

ph+ | bungalow bills case study | 43

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portunity to be involved in a real project and for me, retrofits are a huge part of the picture going forward. I wanted a retrofit project, I wanted to learn as much as I could about it.’

The existing house The McCarron family home, built in 1969, was a typical bungalow. Long, low and compartmentalized, it was rated D2, and had a space heating demand of 324 kWh/m2/yr. In addition to monitoring energy costs in the two years running up to the project, McCarron also monitored temperature and indoor air quality. The average temperature in the kitchen was 17.8 C, relative humidity was 61 per cent, while CO2 PPM averaged 1,050.

The living room wasn’t much better.

‘My bald head is fantastic for picking up drafts. I’m a Liverpool fan, I watch the Champions League at this time of the year.

And in our old living room, with the stove on, the temperatures could be as high as 35 C, but the draft from behind the curtains would turn you into a snowman. So my face would be melted but the back of my head would be frozen.’

44 | passivehouseplus.co.uk | issue 46

It was apparent very early on that this was going to have to be a very deep retrofit. Like so many bungalows, the house had two sitting rooms, separated by a chimney breast, on which the roof was structurally dependent.

Taking down the chimney breast more or less meant taking down the roof. Once the demolition phase was over, the house had been reduced to three external walls and the foundation. All internal walls, along with most of the front wall and the roof had to go.

“In doing that, we saw all the horror shows that you expect to see. We had built-in wall cabinets around the bed, and when they came out, there was mould behind them.

And there was mould behind the units in the kitchen. We had sagging insulation in the wall cavities, and when we cracked up the floor, we found insulation that was the thickness of a Curly Wurly.’

The new wall build-up mixes old with new: blown bead into the existing cavity, internal plastering for airtightness, with external wall insulation doing the heavy lifting.

McCarron says he did a lot of agonising over the windows. The cost uplift between

the basic passive house option and the Internorm units he eventually chose was in the order of €10,000.

‘Looking back, I’m delighted that we went for those. Once you see the quality of the product, you can’t unsee it. The handles in particular were so much better than the handles on the cheaper windows.’

The fact that the Internorm units were uPVC aluclad as opposed to timber aluclad was the clincher. The windows were hung on the outside of the original wall in order to help preserve thermal continuity.

‘I didn’t like the notion of putting timber out there, in case there was any unintended water at play at sometime down the road.’

Decrement delay and overheating The build-up in the new pre-manufactured truss roof is also worth highlighting. McCarron points out that rooms in roofs – where the children’s bedrooms are now situated – are vulnerable to overheating. His build-up seeks to mitigate that risk through decrement delay: reducing the time it takes for external heat to transfer into the house. There’s no less

CASE STUDY

BUNGALOW BILLS

My bald head is fantastic for picking up drafts. In our old living room, with the stove on, my face would be melted but the back of my head would be frozen

than three tons of cellulose insulation in the roof. It’s got more mass than lightweight, petrochemical-based insulations, so it acts like a sink, absorbing the heat from the sun rather than transmitting it into the space.

‘We also have five Velux windows in the house. They were deliberately chosen so that we could purge ventilate the house if we needed to. Over years of observing passive house projects, I’ve seen that a roof light is an excellent way of cooling the building if it did have an overheating issue, which fortunately we don’t.’

These units are five-glazed – a cassette of triple glazed and another gap of double glazed, and remote controlled. Interesting to note too that PHPP modeling prompted a reduction in glazing at the front of the house, and the removal of additional Velux windows from an early version of the plan – again to reduce overheating risk. So far so good: after one summer in the house, air temperatures never climbed above the 25 C threshold. Staying with PHPP, McCarron notes that the process of designing and building his own house opened his eyes to the power of passive house software.

‘A lot of people in the construction industry think of them as compliance tools, they think in terms of ‘What’s my score?’ Really, PHPP is a tool that helps you evolve the design of the house. It took me a couple of years on my journey to learn that properly. To see the impact of that in my own house was really great, because every decision was educated and backed up by evidence.’

The other big advantage of using so much timber-based insulation was a reduction in the building’s embodied carbon score, in particular in the case of the cellulose insulation. Because of life cycle assessment rules, this has little or nothing to do with CO2 stored in the materials, but all to do with the fact that products like cellulose require remarkably little energy and associated CO2 to manufacture.

“Obviously, when you have a retrofit, your

Photos: Internorm / Stefan Hoare

embodied carbon is going to be part of the story because you’re keeping much of the existing structure and you’re not building in a greenfield site, but when you start to use cellulose or wood fibre, you’re going to do so much better.”

He notes too that choosing natural materials didn’t have any adverse impact on cost.

Exceeding airtightness ambitions Achieving airtightness in a retrofit is often a major challenge, but thanks to careful detailing and support from professionals, the team achieved the Enerphit standard on the first attempt, with 0.69 air changes per hour (ACH) – well inside the 1 ACH threshold, and right on the cusp of the 0.6 ACH threshold required by passive house.

‘Roman (Szypura of Clioma House, who did the blower door test) rang me at the time and said, “Well done, Barry. You’ve got Enerphit. It’s a passive house retrofit. But this is a bad result for you because now you have to go after a full passive house.”’

At the time, the heat load in the retrofitted house had been reduced to 10 W/m2 – which

meets the heat load target for the passive house standard. This meant that if McCarron could secure a small improvement in airtightness, he would achieve full passive certification for the project.

The airtightness team carried out some remedial work around screw holes in kitchen units and junctions where the old structure met the new, and a second blower door test confirmed that the target had been met.

Now, remarkably, the retrofit meets the full passive standard.

As part of the process of seeking passive house certification, the project had to be meticulously documented throughout, primarily by taking photographs at every stage.

That’s what put the idea in McCarron’s head: start an Instagram account and share the experience of building passive with the wider self-build community.

‘It was one way of making sure I didn’t drop off on the homework, so every Friday, I did a post, I wrote something up and I put up the photographs. That really kept me on track.’

It also proved to be very popular, and over the months of the build, picked up over

ph+ | bungalow bills case study | 45

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CASE STUDY

3,700 followers (@bungalow_retrofit). It was, he says, a very rich and positive experience.

‘There is a huge thirst for independent information out there…That whole Instagram self-build community bouncing off each other, asking questions – it’s amazing how fertile it is. Of course, the danger is that there are also people out there who are not construction experts communicating things that may not be right.’

As it happens some bona fide construction experts communicated that things are most definitely right with this project, with the house picking up the housing award at the Towards Net Zero Awards in November.

McCarron pays tribute to the range of construction professionals that worked with him on the project, including Ryan Daly of Daly Renewables, Roman Szypura of Clioma House, and Seamus Keenan of Positive Energy Ireland, as well as his contractor, Owen Treanor. ‘He was excellent. He was really open and open minded. He had never built a passive house before, but he kept listening.

And he kept an open mind.”

As Passive House Plus often hears from builders who have built their first passive house, Treanor says the process has changed him.

“Definitely,” he says. “It has given me a whole new way of thinking in terms of junctions and detailing and even in terms of minimising waste. I’m working on new extensions now, and the detailing from Barry’s house is being used again.” Even while still on site with new projects, Treanor can see signs of the benefits his clients will reap. “The heating isn’t on in the extension yet and it’s warmer than the house.”

Treanor says McCarron’s efforts to minimise waste on this project has encouraged him to the opportunities to reduce waste disposal costs. This project arguably blurs the line between a new build and a retrofit, but 25 per cent of the existing building was retained, including 66 per cent of the existing walls. “All rubble and concrete waste went to a project about 400 m from our site to another site for hard standing and back fill,” says McCarron. With waste disposal costs becoming an increasing issue, Treanor points to less progressive approaches to construction and demolition waste. “I remember a builder saying a hole is a very handy thing,” he says, while pointing out that a more circular approach can avoid costs on waste disposal and on acquiring new materials.

Moving back in The family moved into the house in May and are loving the new space. While the look and feel of the house has been transformed, the design team retained that original bungalow profile. Inside, the double height ceilings in the main living area belie what we’ve

46 | passivehouseplus.co.uk | issue 46

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Before: 1 The existing house built in 1969; 2 & 3 mould visible in rooms; 4 the red line indicates a gap in insulation at top of wall; 5 & 6 cavity insulation with massive gap at top including block at wall plate.

come to expect when we walk through the front door of an Irish bungalow. It’s bright and airy, with consistent temperature and perfect indoor air quality.

Having suffered the house’s discomfort before the retrofit, McCarron is acutely aware of the palpable change in living conditions.

“One of the great experiences of living in the house so far has been when you get up in the middle of the night. In the old house you would have got out of the bed and you would have [had to] hop, skip and jump to the bathroom and back because it was so uncomfortable,” he says. “Now you just get up, and what really strikes you is when you put your foot onto the tile, the tile isn’t cold.

The underfloor heating hasn’t been on in the house yet. We’re now 12 October. This morning was the first day with frost and still this morning I would have got up about 5am to go to the toilet and the tiles aren’t cold underfoot. That level of comfort’s there even without the heat.”

While healthy adults may be able to grin and bear the discomfort of typical houses, it’s a different matter for vulnerable occupants such as people with disabilities, elderly

people or young children, whose health is more likely to suffer in suboptimal living conditions. “Doing passive was directly linked to the family motivations,” he says, referring to his three children, Doireann, Daithi and Dylan. “For myself and Aisling it was: do this now for them really to get the good out of it from when they are young.”

The focus was very much on the living conditions his children would experience growing up, and how it might affect their development. “Doireann is seven, Daithi is five and Dylan is three, so that’s 11, 13 and 15 years of excellent indoor air quality levels respectively till they turn 18 – sleeping and living in CO2 levels below 800 ppm.”

One issue McCarron thought long and hard about was kitchen extraction. As Passive House Plus has previously reported , a number of potentially harmful pollutants can be released during cooking, meaning effective air extraction becomes essential. McCarron opted for a recirculating extractor in light of a paper at the 2023 International Passive House Conference showing reasonable extract coverage for recirculating extractor hoods. But in this case the extractor

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WANT TO KNOW MORE? The digital version of this magazine includes access to exclusive galleries of architectural drawings.

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The digital magazine is available to subscribers on passivehouseplus.ie & passivehouseplus.co.uk

1 The house stripped back to three external walls and the foundation; 2 first course of Mannok Aircrete blocks on inner leaf; 3 & 4 when heat is required, it’s delivered via underfloor heating buried in a screed; 5 plastic starter rail to reduce thermal bridging; 6 new Internorm windows hung on the outside of the wall, sat on Alma Vert structural insulation supports; 7 300 mm cavity wall pre installation of bonded bead insulation, with 200 mm KORE EPS70 Silver insulation externally; 8 airtightness taping around windows; 9 KORE EPS insulation cut to measure to insulate the eaves; 10 the new truss roof; 11 Roman Szypura explaining the airtightness work to a team from Net Zero Bau; 12 Pro Clima Intello Plus vapour control membrane to ceiling; 13 cellulose blown in at high density; 14 Thermafleece insulation in service void; 15 insulated supply and extract ducts from MVHR sealed to exterior walls; 16 Diathonite cork plaster to window reveals.

ph+ | bungalow bills case study | 47

Non-combustible mineral clay insulation BUNGALOW BILLS

CASE STUDY

48 | passivehouseplus.co.uk | issue 46

Class A2-s1,d0 Fire rating

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Thermal conductivity 0.034W/mK

For new and refurbished buildings

CASE STUDY

BUNGALOW BILLS

SELECTED PROJECT DETAILS

(above) McCarron’s children Daithí, Dylan and Doireann during the build; a temperature reading in the children’s bedroom pre retrofit; McCarron using a thermal imaging camera phone in the finished home.

is integrated into the hob. With ventilation experts tending to recommend overhead extractors, McCarron added two extracts for the MVHR system above the cooker too, and is replacing filters every three months.

So far so good, he says.

For McCarron, in light of the comfort and energy benefits families can reap in such high performance homes, the decision to go passive should be a no brainer.

“My advice for anyone, if you’re building a new build or you’re retrofitting would be to go the whole hog and to do the passive house thing. I’m forty years of age, and my only regret is I should have done it ten years earlier, instead of procrastinating. And always build to the best standard that you can at any given moment. I don’t think you’ll ever regret it.”

Embodied carbon The McCarrons’ house is about as deep as a retrofit can be, and could almost be considered a new build, given that the floors were dug out and the building stripped right back to the walls. The RIAI 2030 Climate Challenge dif-

fers from the RIBA equivalent which inspired it in one key regard for this project. While the target for smaller dwellings is 625 kg CO2e/ m2, for dwellings over 133 m2, and low density dwellings of up to two storeys, that target is reduced to 450 kg CO2e/m2 – reflecting the fact that large one off houses tend to bring additional environmental burdens.

An indicative analysis of the bungalow’s embodied carbon carried out using PHribbon showed that the building hit 80.5 tonnes of CO2e – or 454 kg CO2e/m2, narrowly missing the RIAI 2030 target for this house.

The biggest contribution came from the building’s concrete products and large PV array, though it’s worth noting that default data for materials was used in both cases. When assessed against LETI’s embodied carbon targets, the building scored 294 kg CO2e/ m2 in terms of upfront emissions – meaning up to the point of the building’s practical completion. As per LETI’s approach for upfront emissions, this figure doesn’t count the sequestered (or stored) CO2 in the biogenic products used like timber, wood fibre and

Client: Barry & Aisling McCarron Architect/engineer: Wayne Funston, Funston Howe Architecture Mechanical and electrical: Daly Renewables Passive house certification: MosArt Project management: SustainABLE Builder: Owen Treanor Construction Electrical: Positive Energy Ireland Airtightness: Atlantic Air / Greenbuild Passive house certifier: MosArt Home Performance Index assessment: Wain Morehead EPS/XPS and cavity fill: KORE Insulation, via Breffni Insulation External insulation system: Sto Aerated blocks and roof tiles: Mannok Thermal breaks: Partel Airtightness membrane, cork plaster, woodfibre, cellulose and wool insulation: Ecological Building Systems Cellulose and airtight membrane installer: Clíoma house Airtight tapes: Ecological Building Systems / Partel Windows and doors: Internorm via Interlux Roof windows: Velux Air source heat pump: Eco Forest, via Daly Renewables Underfloor heating: Roth, via Daly Renewables Heat recovery ventilation: Renson, via Daly Renewables Lighting: Mullan Lighting Sand/cement screed: Micheal Heeney Flooring Interior design: Mags McCarron, Your Home Illustrated Furniture and carpet: Upstairs Downstairs Tiles: Irwins Castleblaney Water conserving fittings: Grahams Hardware Monaghan Sanitaryware: My Life Heat pump: Ecoforest EcoAir PRO 1-7kw ASHP, via Daly Renewables

cellulose, and it also excludes the PV, as LETI regard PV as part of the grid rather than the building, except in cases where the PV array forms part of the roof structure, such as building-integrated PV. The cradle-to-grave LETI total only marginally increases to 298 kg CO2e/m2. This is for a couple of reasons: the benefit of the sequestered CO2 in the biogenic materials is effectively cancelled out by the assumption those emissions are released into the atmosphere at the end of life of the building. And the assumed carbonation of the building’s concrete products at end of life adds a small amount of permanent sequestration to the results.

ph+ | bungalow bills case study | 49

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CASE STUDY

BUNGALOW BILLS

IN DETAIL Building type: 138 m2 1969 bungalow retrofitted and extended to 188 m2 Site & location: Ballinode Village, north county Monaghan Completion date: April 2023 Budget: €360,000 / €1,925 per m2 Passive house certification: Passive house classic (pending) Embodied carbon total: 422 kg CO2e/m2 (when assessed as per RIAI 2030 Climate Challenge, including modules A, B1-B5, and C) Green building certification: Home Performance Index (pending) Space heating demand (PHPP): 27 kWh/m2/yr Heat load (PHPP): 10 W/m² Primary energy demand non-renewable (PHPP): 87 kWh/m2/yr Primary energy demand renewable (PHPP): 50 kWh/m2/yr Renewable energy generation: 27 kWh/m2/yr

Heat loss form factor (PHPP): 3.9 Overheating (PHPP): 1 per cent Number of occupants (PHPP): 5.0 for passive house assessment.

Airtightness (at 50 Pascals): 0.57m3/hr/m2 at 50 Pa / n50 of 0.53 Thermal bridging: First course of Mannok Aircrete blocks on new inner leaf walls, windows and doors bracketed into external insulation line sitting on Alma Vert structural insulation supports/thresholds, cork plaster to the window reveals.

Ground floor: 100 mm sand and cement screed, followed underneath by 180 mm PIR insulation, U-value: 0.11 W/m2K Walls: 300 mm traditional cavity wall construction with 100 mm KORE Fill insulation in cavity, 200 mm KORE EPS70 Silver insulation, StoMIX EWI System. U-value: 0.10 W/m2K Roof: Mannok concrete tiles, timber batten,

Pro Clima Solitex membrane, Gutex wood fibre insulation, Dämmstatt cellulose insulation, Pro Clima Intello airtightness membrane, Thermafleece sheep wool insulation, 50 mm service void/air gap, U-value: 0.125 W/m2K Windows & external doors: Internorm KF410 UVPC Aluclad. Passive House Institute certified.

Overall U-value of 0.84 W/m2K Roof window: Velux certified passive house roof light Heating: Ecoforest EcoAir PRO 1-7 KW modulating air source heat pump, with low temperature heat delivered via underfloor heating.

Ventilation: Renson Endura Delta mechanical ventilation with heat recovery (MVHR) system.

Passive House Institute certified heat recovery efficiency of 84 per cent.

Electricity: 5.92 kWp photovoltaic array.

Excess energy is used for electric car charging or grid export. ph+ | bungalow bills case study | 51

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IN BRIEF Development type: 269 m2 detached dwelling Method: Timber frame, insulated foundations, brick slips, low carbon materials, heat pump, PV Location: Cork City Standard: Passive house classic (pending) Heating cost: €12 per month* * Calculated space heating cost.

See ‘In detail’ panel for more information.

€12 per month

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HOME FROM HOME ARCHITECT TURNS CHILDHOOD HOME INTO CLIENT’S PASSIVE HOUSE Few architects are tasked with knocking their old family home, but for John Morehead, once this difficult decision was made, it was a chance to create a future-proofed new passive house that embraces its stunning natural surroundings and exhibits remarkable attention to detail.

Words: Lenny Antonelli

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Passive house is really important, but it comes second to the architecture sometimes for us

W

hen passive house architect John Morehead received an email from a prospective client, enquiring about the prospect of designing a passive house on the site of Morehead’s childhood home in Cork, he assumed it was a joke.

Morehead is a well-known figure in the passive house community. The house he grew up in, a 1960s dwelling in the riverside suburb of Blackrock, had recently been sold. “I thought it was a family friend winding me up,” he says. But it was not.

The email came from Killian Hurley, a Cork native who is the chief executive at Mount Anvil, a housebuilder in central London. Killian and his wife Maeve had bought the house in 2018, with a view to building a new home for themselves on the site. They had turned up Morehead’s name when looking for a local architect with passive house expertise.

For Morehead, taking on the project was an emotional as well as a practical proposition. His parents moved from Dublin back to Cork in 1965. They bought the site along the marina, and had an architect-friend design a modest brick-clad dwelling, which they called Leeward. They lived there for almost 40 years.

In 2005, Morehead’s parents divided the site in two, and Morehead designed a new low energy house for them on the newly created site next door.

Morehead’s parents moved into that house, called Svendborg, in 2007, and sold their old home. Sadly, Morehead’s father died soon after. Leeward was rented out for a few years, but was not looked after, and was empty when Killian and Maeve purchased it. The area is now highly sought after and has some of the highest house prices in the city.

Killian knew about the passive house standard from his work as a developer and says that if he was going to knock a dwelling, with the inherent environmental impact of doing so, he was keen to make the replacement as sustainable as possible. The couple were also keen on the promise of good indoor air quality.

A difficult decision Morehead and his team at Wain Morehead Architects examined the possibility of ren-

54 | passivehouseplus.co.uk | issue 46

ovating Leeward, but the ground floor was quite low-lying, and the house sits less than 20 metres from the tidal estuary of the Lee. The site is on reclaimed slob-land along the river, created during the construction of a towpath in the 19th century, and will face an increased flood risk in the coming decades.

Extending the lifespan of the site meant knocking Leeward and building a new house with a raised floor level. “It was a dif-

ficult decision as you can imagine, to demolish the house,” Morehead says. “It was a very strange time for me, emotionally.”

But there were good reference points to guide the design of a new home. The waterfront location was one, even though the estuary views are north-facing. The sunny, sheltered, south-facing garden was another.

The neighbouring architecture was a third.

The house is located in an Architectural

CASE STUDY

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Good quality daylighting, light dancing off things, good shading, is very important for the wellbeing of the person living there

Conservation Area, in a row of a dozen oneoff homes. “There’s a lovely eclectic mix of architecture along there,” says Morehead.

“They’re very much of their time. There’s Victorian, Edwardian, early Arts and Crafts.” He wanted to reference these styles and embrace their attention to detail while creating something thoroughly modern.

With its north-facing façade, a back garden that rises steeply at the rear, and lots of mature vegetation, getting more light into the house was a priority. For the northern rooms and terracing, this was achieved by introducing a glazed courtyard into the core of the dwelling, with vertical features to draw light down. Maeve Hurley took on the role of finishing the design of the courtyard and selecting a tree to plant at its centre.

Doughnut design The small, partly-glazed courtyard is a work of art, with vertical larch cladding, a bench for seating, and pedestals referencing the

old greenheart fenders on the quay wall. It sits in a direct line between the front door and the rear sliding door, creating an axis of light and vegetation running right through the house. “The courtyard has been a great success, it’s just gorgeous, it keeps drawing you into it,” Morehead says.

But it was “a nightmare from a passive

Photos: Gabrielle Morehead, John Morehead, Owen McSwiney

house perspective,” he says. It essentially turns the house into a doughnut, with one external envelope on the outside, and another on the inside. This meant more surface area from which heat could escape, and more junctions to be made airtight.

“Passive house is really important,” Morehead says. “But it comes second to the archi-

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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

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1 The original 1960s house; 2 site cleared in preparation for the new build; 3 insulated foundation system prior to concrete pour; 4 foundation complete; 5 timber frame walls with Smartply Propassiv OSB airtight layer; 6 underfloor heating; 7 Smet Sudanit 280 hemihydrate screed; 8 taping around windows; 9 sill to timber cladding; 10 Gutex wood fibre insulation; 11 Siga Majpell airtightness membrane and taping; 12 brick slip installation in progress; 13 MVHR ducting; 14 the south terrace; 15 flat roof and solar PV array; 16 arrival of the silver birch tree for the courtyard at the centre of the house.

56 | passivehouseplus.co.uk | issue 46

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With the principles of biophilia, we still have the same attention to the detail that the Edwardians did

tecture sometimes for us.”

The courtyard features triple glazed sliding glass doors from Schüco, and on hot days, these can be opened, along with the rear sliding doors, to create a stack effect and cool the building.

Morehead was keen to make sure the building was fit for a warming climate (it is interesting to note that, by using site specific climate data rather than generic data from Cork Airport, it was easier to meet the passive house standard. See figures for energy demand from ‘In detail’).

But he did not want to install active cooling. He was wary that, in our damp climate, mechanical cooling creates a risk of interstitial condensation, lowering the temperature of surfaces and triggering the dew point at which water vapour condenses.

At Leeward, the project team learned the hard way just how sneaky condensation can be. When the intermediate floor slab was slow to dry, the team inserted moisture probes to find out why. They found the temperature of the slab was lower than the surrounding air — water vapour was condensing on its underside, soaking into the Gutex wood fibre insulation beneath. It was a problem easily solved by cranking up the underfloor heating, but one that could have been much more serious.

Attention to detail The build suffered from other slowdowns — Brexit, Covid, and a difficulty in finding skilled subcontractors — but the finished house scored a blower door test result of 0.45 air changes per hour, an exceptional result given the number of junctions. “The detailing had to be very robust everywhere,” Morehead says. He praises his builder, Lough Contractors, for their “top class attention to detail”.

The timber frame was built by Eco Timber Systems, whose factory is just 15 kilometres away. And the twin-stud walls feature 300 mm of cellulose, manufactured by Ecocel less than three kilometres from the site.

The twin stud was key to ensuring there was enough insulation to meet the passive house standard. Airtightness is provided by Smartply Propassiv OSB, rather than membranes.

“We’ve always had a preference to use OSB as an airtight layer,” says Stephen Spillane of Eco Timber Systems. “It’s easy to apply tapes to. It’s very robust, you can even fix electrical socket boxes, etc directly to it without any compromise in the airtightness. A membrane can be damaged much easier and sometimes goes by unnoticed.” Spillane says that some of the architectural features, such as cantilevered corner windows and doors, required especially careful detailing.

The ground floor, meanwhile, was raised 310 mm above its previous level. It has an EPS insulated foundation system from Cavan manufacturer KORE. Space heating is provided by a Hitachi air-to-water heat pump, ventilation from a Zehnder mechanical ventilation with heat recovery system. There’s also a Showersave wastewater heat recovery unit — essentially a heat exchanger that recovers heat from wastewater going down the shower drain, and uses it to warm incoming mains water, and the cold supply to the shower mixer. There’s also an Amerisolar solar PV

array with an average annual output of 1,979 kWh — which can be extended further on the western monopitch roof — and two electric car chargers.

Biophilia Killian Hurley praises his architect’s “attention to minute detail”, and this is perhaps best expressed in the way the house interacts with its environment — its appreciation for nature, or biophilia, as Morehead likes to say. “[Killian and Maeve] were very taken by the Edwardian houses down the road,” Morehead says. “We were designing a modern house, knowing they love the intricacies of those properties. With the principles of biophilia that we apply, we still have the same attention to the detail that the Edwardians did.”

This meant embracing views of the water and the garden, and retaining the mature vegetation on site (the build team were careful to retain the large Scots pines in the front garden). Maeve Hurley selected a silver birch tree for the courtyard at the centre of the house,

ph+ | leeward case study | 57

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CASE STUDY

and when landscaping is complete, the view from the front door through the courtyard will extend out back to a timber-framed pathway, covered with climbing plants. A winding path will lead through thick vegetation to the escarpment at the back of the garden.

The new Leeward sits on a similar footprint as the original dwelling, but is larger at 269 m2. It embraces the estuary views while keeping the glazing ratio sensible on this north facade. But there is a new outdoor terrace here at first floor level, with views over the river. And there are clever nods to neighbouring properties. The western element of Leeward is aligned with its neighbour to the west, Svendborg, while the eastern element is aligned with Carriglee, to the east. This creates a slight ‘crank’ in the plan. The house’s timber and zinc cladding doff their cap to Svendborg, the brick cladding to the Edwardian dwellings nearby. The steep roof of the western element also references the gables of neighbouring homes.

for energy, it’s for humanity as well.”

The more extensively glazed south-façade looks out into the sunny, sheltered and lushly vegetated garden, with its outdoor dining terrace. Downstairs, the main living and dining areas face south too. A basket weave oak floor that was salvaged from the demolished house has been reused here.

Upstairs, the emphasis was on creating useful, adaptable rooms. There’s a study with a pull-out sofa for guests, and a family room with bunkbeds hiding behind a sliding door.

A south-facing, first floor terrace overlooking the garden is accessible from two of the

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upstairs bedrooms, with an external spiral stair connecting to the gardens below.

Killian and Maeve had just moved in as Passive House Plus went to press, and according to Killian they are loving the house, and especially the courtyard.

“To have a tree in your kitchen or living room is a nice one,” Killian says. “We’re in there a couple of weeks. We’re just loving the space. The light is particularly good. There are full height windows in a lot of the rooms, and that combined with the atrium gives a lovely feel to the house.”

For energy & humanity Morehead and his team thought hard about how natural lighting would work in the space. “Good quality daylighting, light dancing off things, good shading — all of that stuff is very important for the wellbeing of the person that’s living there,” he says. “How the light works around the house — it’s not just

SELECTED PROJECT DETAILS

Client: Killian & Maeve Hurley Architect: Wain Morehead Architects Civil/structural engineer: Horgan Lynch Consulting Engineers Main contractor: Lough Contractors Quantity surveyors: Richard Leonard & Associates Mechanical contractor: Robert McGarry Plumbing Electrical contractor: Gar Callanan Electrical Airtightness tester/consultant: Building Environmental Resources Build system supplier: EcoHomes Thermal breaks: Bosig, via Ecological Building Systems Roof insulation: Unilin Insulation / Xtratherm Additional roof insulation: Ecocel Insulated foundation system: Kore Airtight board: Medite Smartply Airtightness membranes and tapes: Ecological Building Systems / Siga Heat pump and underfloor heating system: Pipelife Ireland Heat recovery ventilation: Zehnder, via Clean Energy Ireland Screeds: Smet Windows: Zylefenster, via Walter Power

Embodied carbon Shane Fenton of Wain Morehead Architects calculated the building’s embodied carbon using an early iteration of the new Irish national methodology for whole life carbon assessment, which is being developed by the IGBC under the Indicate project.

The scope was as per the EU’s Level(s) framework, and the cradle-to-grave total came in at 155 tonnes of CO2e, or 594kg/m2. As per the RIAI 2030 Climate Challenge requirements the results excluded emissions from operational energy and water use (modules B6 and B7).

As product level embodied carbon data is currently harder to come by for mechanical, electrical and plumbing services, at present the tool uses generic estimates for these elements, based on weight of each material type.

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CASE STUDY

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IN DETAIL Project name: Leeward Building type: 269 m2 detached dwelling, off site timber frame construction Site type & location: Urban site, Cork Completion date: 01/08/2023 Budget: Not disclosed.

Passive house certification: Passive House classic certification pending Space heating demand: 11.01 Wh/m2/yr (site specific climate data), or 12.92 kWh/m2/yr (Cork Data) calculated using PHPP Heating load: 8.69 W/m2 (site specific climate data), or 10.11 W/m2 (Cork data) calculated using PHPP Primary energy non-renewable: 37.82 kWh/m2/ yr (site specific climate data), or 38.45 kWh/m2/yr (Cork Data) calculated using PHPP Primary energy renewable: 20.33 kWh/m2/yr (site specific climate data), or 20.70 kWh/m2/yr (Cork Data) calculated using PHPP Heat loss form factor: 4.05 calculated using PHPP Overheating: 0 per cent of year above 25 C (site specific climate data), or 3 per cent of year above 25 C (Cork data) calculated using PHPP Number of occupants: Two adults Energy performance coefficient (EPC): 0.031 (0.30 threshold) Carbon performance coefficient (CPC): 0.019 (0.35 threshold) BER: A1 (4.75 kWh/m2/yr) Environmental assessment method: N/A Embodied carbon: 492 kgCO2e/m2, calculated using PHribbon.

Measured energy consumption: Data not yet available Space heating costs: Calculated at €148.91/yr, based on the calculated space heating demand of 11.01 kWh/m2/yr and stated heat pump

seasonal performance factor of 569 per cent.

Based on a 24-hour rate of 31.54c per kWh from Yuno Energy, this figure ignores the contribution to running heat pump from the solar PV array.

Airtightness: n50: 0.45 ACH at 50 Pa AP50: 0.47 m3/hr/m2 at 50 Pa Thermal bridging: All Psi values calculated.

Insulated foundation system with timber frame construction superstructure. Thermal bridging reduced by optimising window junction details, installation of wood fibre board externally and Bosig Phonotherm at window sills/thresholds.

Y-value (based on ACDs and numerical simulations): 0.020 W/m2K Ground floor: 50 mm Smet Sudanit 280 hemihydrate screed, over Visqueen vapour barrier, over 90 mm Xtratherm Thin-R XT-UF (thermal conductivity 0.022 W/mK), over 70 per cent GGBS RC concrete slab, over 350 mm KORE Airfloor EPS100 insulated foundation system over, Necoflex RMB400 radon barrier.

U-Value: 0.071 W/m2K Walls: Factory-built timber frame with 22 mm larch cladding externally / Likestone Capri brick slips on Cemrock Extreme carrier boards, followed inside by 44 x 50 mm treated battens and counter-batten, Proctor Facadeshield UV breather membrane, 22 mm Steico Universal wood fibre board (thermal conductivity 0.040 W/ mK), 2no. 90 x 44 mm twin stud timber frame with full fill Ecocel cellulose (300 mm overall) (thermal conductivity 0.032 W/mK), 12.5 mm Smartply Propassiv OSB taped and sealed (airtight layer), 45 mm service cavity, 15 mm Gyproc Wallboard internally. U-value: 0.102 W/m2K Pitched roof: Standing seam VMZinc, 125 x 25 mm rough sawn boards over, 50 x 50 mm battens, over Icopal All Zone breather membrane, 354 mm open web joists with full fill Ecocel cellulose insulation (thermal conductivity 0.032 W/mK), 12.5 mm Smartply Propassiv OSB

taped and sealed (airtight layer), 35 x 50 mm battens, 15 mm Gyproc Wallboard internally.

U-value: 0.15 W/m2K Flat roof: Sarnafil G410 PVC membrane over, 190 mm Xtratherm Thin-R TR/MG tapered flat roof insulation (thermal conductivity = 0.024W/ mK), Sarnavap 5000e AVCL adhered to 18 mm plywood, 219 mm open web joists full filled with Knauf Loft Roll 44 insulation (thermal conductivity = 0.032W/mK), Siga Majpell (airtight layer) with 15 mm Gyproc Wallboard internally.

U-value: 0.081 W/m2K Windows and external doors: Zylefenster Europa 92 triple glazed alu-clad timber windows, Zylefenster Sky triple glazed alu-clad lift and slide units & Schüco ASE 80.HI aluminium lift and slide units. Overall Uw: 0.92 W/m2K Roof windows: Two EOS Rooflights.

Uw: 1.28 W/m2K Heating system: Hitachi RWD air-to-water heat pump with SPF of 569 per cent supplying underfloor heating. Electric towel radiators to bathrooms.

Ventilation: Zehnder ComfoAir Q600 heat recovery ventilation system - Passive House Institute certified to have an effective heat recovery efficiency of 84.4 per cent Water: Domestic hot water provided by Hitachi air-to-water heat pump, Showersave waste water heat recovery system installed. 3,000 litre rainwater harvesting tank for use in toilets and external irrigation.

Electricity: Seven Amerisolar 410W PV Panels with average annual output of 1,979 kWh. No storage, electric car charging, and excess electricity exported.

Sustainable materials: Timber frame using FSC certified timber, wood fibre board, cellulose insulation, 70 per cent GGBS cement.

ph+ | leeward case study | 61

ZERO CARBON

INSIGHT

MUCH ADO ABOUT NOTHING IS ZERO CARBON CONSTRUCTION ACTUALLY POSSIBLE? As the world edges ever closer to the precipice of runaway climate change, some sustainability terms have moved from relative obscurity towards the mainstream of marketing and public discourse – and none more so than zero carbon. But is zero carbon construction a real prospect, or is it just wishful thinking?

Words: John Butler and Andrew Simmonds

What is a net zero carbon building? Attempts at a definition are underway in the UK and Ireland In the UK, a proposal for a net zero carbon building standard is being developed by a group of prominent industry bodies.

For more information visit www.nzcbuildings.co.uk/. A full list of characteristics and metrics for this proposed standard are shown in the technical update and consultation document, including limits on embodied carbon and operational energy, and minimum targets for aspects such as on-site renewables, demand flexibility, for example. You can read the document at: tinyurl.com/ysft3aec.

In Ireland, the IGBC recently held a consultation on a proposed net zero carbon building definition, and is processing the results.

This can be read at: tinyurl.com/ IGBCnetzerocarbon.

62 | passivehouseplus.co.uk | issue 46

I

ncreasingly claims are made that some buildings are zero carbon in their construction (as opposed to being operationally zero carbon). The incorporation of sequestered biogenic carbon in large quantities of plant-based materials (carbon that has been removed from the atmosphere and stored in the structure of plants while they grow) is seized upon as evidence that the resulting building is zero carbon or even ‘carbon negative’.

Such claims are usually based on the idea that more carbon is stored in the materials used to construct the building than was emitted to create those materials and assemble them into the building.

While this feels like it might make sense the reality is much more complex, making such claims deeply problematic.

Is guidance aligned with standards?

In some areas planning requirements or guidance are being developed to encourage zero carbon development, in both operational and embodied terms. It’s a laudable aim. However, poorly worded guidance can lead to increased misunderstanding of what is really entailed in attempting to achieve genuinely low carbon construction.

The main standards setting out how to calculate the carbon emissions of products and whole buildings state with increasing clarity that the ‘negative emissions’, i.e., the sequestered carbon of biogenic materials, may only be reported for projects when the whole carbon life cycle is accounted for.

These key documents are: • EN15804+A2 ‘Sustainability of construction works: Environmental product declarations - Core rules for the product category of construction products’.

• RICS ‘Whole life carbon assessment (WLCA) for the built environment’.

In fact, EN 15804+A2 puts it the other way around: if a product contains biogenic carbon, then you must account for the whole life cycle. Additionally, it states that the stored carbon cannot be reported for products coming from native forests (carbon emissions resulting from harvesting such resources are reported under “land use and land use change emissions”), and the RICS methodology requires that in the case of timber, only stored carbon in FSC or equivalent certified sustainable forestry

Photo: Black Salmon / Shutterstock.com

INSIGHT

(above) A strong carbon buffering argument can be made for systems such as the Ecococon modular straw bale system, which use straw, an annual rotation crop.

can be counted.

Creative accounting Sticking to the approach set out in the standards is crucial to avoid misrepresenting projects and downright creative accounting. What do we mean by ‘creative accounting’? For example, suppose the negative figures for stored carbon are added together with the upfront carbon emissions , and it happens to be the case that more carbon is stored in the building than was emitted in delivering the building – as can happen in buildings where there’s very high use of biogenic materials. The stored carbon may appear to cancel out the emissions, and may even be used to claim the building is ‘carbon negative’ – perhaps evoking an emotional concept of it actively sucking carbon out of the sky? While this may look appealing to marketing departments, it simply doesn’t reflect reality. The reality is that the manufacture of any product (including those made from plants) results in some emission of carbon now.

Sticking to a standard approach is also the only way any comparison can be made between projects to aid more focused and effective research and development in the industry.

There is confusion around the importance and timing of emissions. Carbon stored in timber materials will have been absorbed over many decades of growth, and it will take many decades of growth to re-

peat the process after the timber has been felled, extracted, and used in a building. By contrast, in the case of fast-growing crops used in construction such as straw, sequestration takes place over the previous annual growing season and is regrown just as fast.

As electricity grids and manufacturing industries decarbonise (decarbonising the UK electricity grid is progressing faster than the manufacture of common building materials) then the level of emissions from the manufacturing and processing of material for construction may reduce.

But again, that decarbonisation process is happening over decades, and much is still uncertain – bringing us back to the point that right now pretty much all construction causes immediate emissions to a heavily carbon-polluted atmosphere.

LETI 2030 design target LETI 2030 design target LETI 2020 design target LETI 2020 design target

Office

A++ A+ A B C D E F G

<100 <225 <350 <475 <600 <775 <950 <1100 <1300

thropogenic carbon emissions on climate change and make wise use of resources over time, we need to make the fastest reductions in emissions now, and now means within the next ten years. But we still cannot ignore future emissions. It is essential that the potential release of carbon at the end of life is considered.

Genuine low carbon construction means now and in the future The LETI approach to embodied carbon targets and benchmarking is useful here, where a building must meet targets both for upfront and life cycle embodied carbon.

They suggest that by 2030 at the latest we should be building to their A rating, with A+ and A++ still to aspire to – arguably where we should be aiming already.

Band A, applied to residential buildings, allows up to 350 kgCO2e per square metre of gross internal area (GIA) for upfront carbon and 530 kgCO2e/m2 (GIA) for life cycle embodied carbon.

The lower allowance for upfront emissions addresses the need to reduce real-terms emissions right now.

The increased allowance for life cycle embodied carbon reflects not just the potential future emissions of the stored carbon from disposal or processing of all materials at the building’s end of life (EOL), but also emissions from product replacements and maintenance during a building’s life.

End of life – future planning It’s also important to note that any biogenic carbon in a product or building will eventually be released at the end of the lifecycle of that product or building. Again, on timing of the carbon ‘leakage’: carbon from badly detailed timber cladding or landscaping features will find its way to the atmosphere quicker than the timber structural elements or natural-fibre based insulations or linings of a well-detailed and well-built building.

Even if a biogenic material is removed from a building and re-used intact in another building, from the carbon-accounting perspective the carbon is still ‘released’ from the first building (which is no longer Biogenic materials storing its precious carbon-cargo), and There are many discussions to be had the ‘negative emissions’ value is then rec- around the storing of carbon long term in ognised in the carbon accounts of the new building materials, but the main issue is building. When planning a building we that while many tonnes of carbon might be can (and should) design with a clear intent temporarily locked up in the plant-based for reuse or recycling of the materials in it, materials in a building, they won’t stay helping future generations (or our future locked up forever. Clearly this practical reselves) when the building is ultimately de- ality is in direct conflict with the simplistic constructed. They won’t thank us for build- notion of zero carbon construction. ings and materials that are hard to repurWith plant-based materials (and many pose, reuse or recycle! non-plant-based ones) there are further carbon, A1-5 (excluding We must accept that we can’t knowUpfront what embodied emissions associated withsequestration) land use and land Residential Education will happen however well we design – Band but useOffice change.

Another welcome Retail addition to (6+ storeys) <100 <100 <100 emissions <100 A++ that is no excuse not to think long term. AcEN15804 +A2 is that these must <225 <200 <200 <200 A+ cess to resources appears almost certain to be now be accounted for and stated separately.

LETI 2030 design target <350 <300 <300 <300 A <475 <400in soil<400 <425 much more difficult in the years ahead. B Carbon stored can be released by LETI 2020 design target <600 <500 <500 <550 C Clearly, to limit the worst impacts of ancultivation.

Any existing vegetation re<775 <675 <625 <700 D E F G

Upfront embodied carbon, A1-5 (excluding sequestration) Band

ZERO CARBON

Residential (6+ storeys) <100 <200 <300 <400 <500 <675 <850 <1000 <1200

<950 <1100 <1300

<850 <1000 <1200

<750 <875 <1100

<850 <1000 <1200

Life cycle embodied carbon, A1-5, B1-5, C1-4

Education

Retail

Band

Office

<100 <200 <300 <400 <500 <625 <750 <875 <1100

<100 <200 <300 <425 <550 <700 <850 <1000 <1200

A++ A+ A B C D E F G

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build target RIBARIBA 20302030 build target

Residential (6+ storeys) <150 <300 <450 <625 <800 <1000 <1200 <1400 <1600

Education

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<125 <250 <380 <535 <690 <870 <1050 <1250 <1450

Life cycle embodied carbon, A1-5, B1-5, C1-4 Band

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<125 <250 <380 <535 <690 <870 <1050 <1250 <1450

(6+ storeys) Figure 1: LETI’s upfront and cradle-to-grave carbon targets

RIBA 2030 build target

<150 <300 <450 <625 <800 <1000 <1200 <1400 <1600

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ZERO CARBON

INSIGHT

achieve the aim, whether that is structure, insulation, or weather proofing.

Whatever type of material is used it is vital to use the smallest amount necessary to safely, effectively and durably achieve the aim

moved to make way for crops will result in carbon emissions, and there are also potential biodiversity impacts from land use and land use change.

Carbon release buffer However, there is a case to make that the biogenic carbon in building materials can provide a useful carbon release buffer. Using materials made from plants that reduce the amount of carbon in the atmosphere – and then storing that carbon in buildings even temporarily – may be beneficial as it slows the rate of release of that carbon.

The exact length of storage is uncertain, tied to the future life of that building and any decisions or disasters that may befall it. But when left to decompose, the plant material releases its carbon back to the atmosphere within a few years. Incorporated into a building, it could be locked up for anything from a couple of decades to hundreds of years.

Quality of construction also plays a significant role here, to ensure a building that can last for the longest time possible, and with the fewest product replacements during its life. Ultimately, it will still be released but there is large potential to slow and delay that release in real terms.

Using resources efficiently As has been clearly written about before this does not mean we should use as much plant-based material as possible. Sensible and efficient use of any resource is critical, to avoid the immediate impacts caused by its production. The potential biodiversity impacts of any material must also be considered; the less material is used, the lower those impacts are likely to be.

Using recycled materials – and designing buildings to enable re-use of materials – also plays an essential role in reducing carbon emissions and extraction of new material.

Whatever type of material is used it is vital to use only the smallest amount necessary to safely, effectively and durably

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Speed of sequestration The speed of growth of a plant used to make a building material needs to be considered, and whether that plant would be more effective at storing carbon if it remained a growing plant.

The common example is timber, or as it’s known before it becomes a building product: trees. A tree is most effective at storing carbon while it remains alive and growing. Only around 50 per cent of the carbon stored by a growing tree is contained within the part of the stem used to produce timber products. The rest is released back into the system through decomposition or combustion after harvest, though there does also appear to be a degree of increased carbon storage in rotation-cropped forest land over time. The carbon that is stored in trees has been absorbed slowly over decades – but can all be released in one burst at the end of life of a building.

This points strongly to the use of annual – or perennial but annually harvested – crops wherever possible (with longer rotation crops such as trees only used where necessary, such as to provide structure, and in the smallest quantity necessary to safely and effectively do the required job). Such annual crops have stored all their carbon in the growing season immediately preceding their harvest. The carbon stored in the residue from these crops is frequently released back to the atmosphere within a short cycle – for example where the residue is allowed to rot or is burned (or used as animal bedding and then allowed to decompose, etc.).

Locking such plant materials in a building prevents that release and keeps the carbon stored for the life of a building.

Where a building efficiently uses plantbased materials from annual-growth crops in place of non-plant-based materials, it has maximised the storage of recently and rapidly absorbed carbon. Such a building is making the most of its potential to contribute to that useful buffering of atmospheric carbon. Ultimately though, it isn’t, and can’t be. That stored carbon will always be released from the building in the end.

There is no zero impact building We need the construction sector to get better at understanding this. Any building results in emissions and biodiversity impacts.

We should always seek to minimise those first and foremost.

We need to think in terms of carbon stewardship in building design and material choices. The choices we make need to reduce atmospheric carbon now, and consider what will happen to stored carbon throughout the

life cycle of a building and beyond.

Only once that is done can the amount of sequestered carbon be stated as a separate figure (an indicator of the amount of atmospheric carbon buffering that building provides), with the understanding that however large a negative number it may technically be – and whatever the lifespan of that building – the carbon is only held temporarily within its structure.

What about offsetting?

This understandably remains a controversial area. Even if the principle of offsetting (absorbing carbon in one place to offset or balance carbon emitted elsewhere) is accepted, it must never be used to excuse excessive resource use. But, if resources have been used as efficiently as possible and plant-based materials are used, is there a case for then offsetting the residual emissions that do occur?

As laid out above, storing carbon from rapid-rotation plant materials in a building can provide a useful delay to that carbon’s release. It cannot be used to offset the emissions caused by its construction, as that stored carbon will ultimately be released.

Unrealistic scale A residential building of 120 m2 GIA achieving a LETI ‘A’ rating for both upfront and life cycle embodied carbon would result in emissions of around 42 tonnes of upfront carbon, with a further 21.6 tonnes emitted by the end of life of that building.

Across Europe and the UK, the average annual carbon sequestration rate across different types of forest is 3.2 tonnes CO2 per hectare per year.

So, it would take a hectare of average European forest 13 years to absorb the upfront emissions of the relatively low carbon house described above. In case that doesn’t sound too bad, consider that 204,530 houses were built in the UK in 2022. Even if all of these were somehow achieving LETI ‘A’ rating for upfront carbon emissions, that would amount to 8.6 million tonnes of CO2 released in one year. To sequester those new emissions within the same 13 years would require one hectare of new forestry per house – or rather an equivalent amount reaching sufficient maturity every year to provide the required level of sequestration.

That’s an area 1.3 times the size of Greater London requiring forestation every year, just to ‘keep up’ with the annual upfront emissions of housing. And that’s ignoring emissions resulting from external landscaping, access, infrastructure etc., which could be significant in their own right – not to mention non-domestic construction.

This is absolutely not to suggest that we

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Uncertainty Calculating the type and size of forestation needed in this theoretical scenario is complicated. The figures above are based on average sequestration rates across Europe, and forestry of average age. Outside the averages, generally the rate of tree biomass growth – and of carbon sequestration – increases with the size of tree but there is some evidence that the rate of sequestration is reduced in forests of mature big trees , partly due to there being fewer trees per area of mature forest. In theory there may come a point in the life cycle of a tree in a managed forest whereby it will continue to store a greater amount of carbon if removed from the forest, making way for new younger trees at a greater density. But cutting that mature tree down also causes carbon emissions, from the unused biomass (roots, offcuts) and from disturbed soil.

There is other evidence that reducing forest, management increases the amount of sequestration in that forest however the same study found that ceasing all management of forests would only offset four years of global carbon emissions.

The situation is further complicated by a changing climate affecting the stability and predictability of carbon stored in land and forestry. As figure 2 shows, removals of carbon from all land-based sources in the EU (figure below the line) have been falling overall in recent years with a marked decrease in carbon sequestered in forest land. Currently this trend is predicted to continue, though perhaps with different management and planting policies it could be improved.

The Czech Republic has been hit by what the UNFCCC describes as “extreme drought-induced accelerating bark-beetle outbreak calamity (since 2015)”, resulting in land-use, land-use change, and forestry (LULUCF) emissions going rapidly from 6,964 tonnes of CO2e stored in 2015 to 11,268 tonnes emitted in 2020.

Other countries have seen an increase in bark beetle activity too, and with changing climatic conditions it could spread further.

It’s complicated The point is: it’s complicated and problematic to assess how effective offsetting is, or how much offsetting is required. Basic calculations indicate huge areas of forestry would be necessary just to provide carbon sequestration facilities. Although

management of these areas could provide some timber for construction, presumably further additional areas would be required to provide for increasing use of timber in construction.

Again: any materials we use must be used

Million tonnes of CO2 equivalent (Mt CO2e)

shouldn’t plant trees or increase other crucial means of drawing carbon from the atmosphere such as peat bog restoration or rewilding (which also increase biodiversity), but it highlights the scale of offsetting necessary.

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as efficiently as possible.

Offsetting at the speed needed to avoid emissions now and within the next 10 years is unrealistic. Which leads to difficult questions about what we should be building, and how.

200 100

Other land Settlements Wetlands Grassland Cropland Harvested wood products (HWP) Forest land Other Projections with existing measures (WEM) Projections with additional measures (WAM) Land use, land use change and forestry (LULUCF) Approximated emissions for LULUCF

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Figure 2: EU emissions and removals of the LULUCF sector by main land use category.

Source: EEA

Our recommendations • Carbon emissions at any life cycle stage must be reported in line with existing standards: EN15978, EN15804+A2, RICS Whole Life Carbon Assessment in the Built Environment.

• Report kg CO2/m2 and total tonnes emissions. Additionally reporting tonnes emissions per occupant would encourage efficient sufficiency and sensible use of space.

• Stored carbon must never be included in a net figure when reporting upfront carbon (life cycle stages A1-A5, or ‘cradle to practical completion’ of a building). It must only be reported as per the standards/guidance above, i.e.: as a separate figure only.

• There should be targets for upfront and life cycle carbon in any local or national guidance, with both targets requiring to be met.

• These targets should be rapidly reduced to the smallest level to ensure the most rapid decarbonisation possible.

• LETI A+ and A++ should not be considered future aspirational targets but as a representation of where we urgently need to be.

• Retrofit before newbuild. Where demolition is proposed, whole life carbon calculations (combined embodied and operational emissions) must be able to clearly demonstrate that a new building will have a lower carbon impact than a retrofit of the existing building to provide the same floor area as the proposed newbuild.

• Report rapidly sequestered biogenic carbon separately from that in timber products.

• Rapid growth biogenic materials should substitute higher carbon materials effectively, not be used in excessive amounts just to claim a greater stored carbon credit.

• Explore ways of rewarding carbon release buffering resulting from use of rapid-growth/rotation biogenic materials and their associated carbon storage – whilst ensuring that materials are only used as efficiently as possible.

• Operational energy and resulting emissions must be reduced radically alongside reducing embodied emissions.

• External offsetting should never be used as a substitute for reducing actual emissions from construction to the lowest level possible. Whilst there are planting, land use, and forestry practices that can increase stored carbon, there are many uncertainties involved. Such schemes need to be carefully planned to ensure they are genuinely effective (e.g., tree planting in the right place, on poor quality land with low prior carbon retention; compared to tree planting in the wrong place where it can lead to increased emissions from land that previously had high carbon storage value.

• Maximise potential to use recycled materials in new construction or retrofit and to enable reuse and recycling of building components at the end of life of a building.

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Carbon first, fabric second HOW TO DECARBONISE THE UK’S HOUSING STOCK Rapidly decarbonising our cold, leaky dwellings is the greatest challenge facing the UK’s building industry, one fraught with complexity and risk. Now the AECB, one of the UK’s leading green building associations, is aiming to chart a new course through these choppy waters.

by Lenny Antonelli for the Association for Environment Conscious Building (AECB)

W

hat is the best way to decarbonise the UK’s homes? This question has sparked heated debate over the past year.

On one side are those who believe we should deep retrofit dwellings through insulation and airtightness measures, slashing their energy demand and making them more resilient, more comfortable, and less vulnerable to fuel poverty. In other words, put building fabric first.

On the other side, those who say retrofit is simply too slow and complex, that we should

66 | passivehouseplus.co.uk | issue 46

worry less about energy efficiency and prioritise getting low carbon heat — in particular, heat pumps — into homes as quickly as possible. So, who is right? Arguably, both are.

The evidence shows that, done well, deep retrofit shrinks energy demand and improves the lives of building occupants.

But so-called ‘heatpumpification’ is a faster and cheaper way to reduce the carbon footprint of buildings.

Now, the AECB is aiming to forge a middle way, creating a pathway for homes to get a

heat pump and shallow retrofit now, but prepare for a deep retrofit in future. The group has relaunched its CarbonLite (Carbon Literate Design and Construction) standards, providing three pathways to better buildings.

CarbonLite Retrofit step-by-step In the new step-by-step approach to CarbonLite Retrofit (CLR), the home is fitted with a heat pump and good ventilation initially and receives just enough insulation and draughtproofing to ensure the heat pump operates

Photos: Trystan Lea and Glyn Hudson

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(Opposite, clockwise from top) Two ‘heatpumpification’-based retrofits in Llanberis, Gwynned. The exterior of Tystean Lea’s house, which he did not insulate; Lea installed some large surface area radiators; and retrofitted a Mitsubishi EcoDan heat pump; Glyn Hudson’s house features a Samsung Gen 6 air source heat pump. Both homes are listed on heatpumpmonitor.org, with 30 day mean COPs of 4 or over at the time of writing in December.

Figure 1: Retrofit scenario - two waves Figure 1: Retrofit scenario - two waves number retrofitted/yr

1,400,000

efficiently and affordably (step one). A sensible plan is developed for the building to reach the full CarbonLite Retrofit standard in future (in a single second step, or multiple steps).

CarbonLite New Build A rigorous new build standard, with a space heating and cooling target of 40 kWh/m2yr (by comparison, the passive house classic standard requires 15 kWh/m2yr).

The CarbonLite standards are all based on the rigorous passive house methodology and require energy modelling using the Passive House Planning Package (PHPP). CarbonLite standards can also be applied to non-domestic buildings.

Fabric first or fabric second?

The AECB has a long history with building standards. The group first launched its CarbonLite Bronze, Silver and Gold standards in the mid 2000s, to reflect UK-specific building types and the skill profile of the UK’s building industry. It then launched the Passivhaus Trust in 2010 to mainstream radical energy efficiency, leveraging the international momentum that had built up around the German standard. The CarbonLite Retrofit standard was launched in 2021.

But the latest incarnation of CarbonLite Retrofit marks a shift from the AECB’s fabricfirst roots. The CLR step-by-step approach prioritises quick and effective climate-action, putting the low-carbon heating system first (including the heat emitters, e.g., radiators or underfloor heating), enhanced by modest fabric and ventilation measures. Chief executive Andrew Simmonds is pragmatic about why the AECB has changed its approach.

“Our culture and institutions are not changing fast enough to safeguard society from peak oil and the shockingly fast effects of ever worsening climate breakdown,” he says. “There is a profound failure of national political leadership, a lack of science-based policymaking, and a desperate shortage of the necessary skills — all necessary to deliver

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CLR step-by-step

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CLR step-by-step → CLR completed

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Figure 1. An AECB stock model scenario showing two retrofit waves to the English housing stock. In the first wave, 50 per cent of stock takes the step-by-step approach to CarbonLite Retrofit, while 25 per cent of stock goes straight to full CarbonLite Retrofit. In the second wave, the projects which had already started the step-by-step approach are upgraded to full CarbonLite Retrofit by the middle of the century.

Figure 2: operational & embodied carbon of retrofit Figure 2: operational & embodied carbon of retrofit pathways pathways tonnes CO2e per year

CarbonLite Retrofit completed A whole-house deep retrofit standard, designed to dramatically cut energy use, with a maximum space heating and cooling demand of 50 kWh/m2yr (by comparison, the Passive House Institute’s Enerphit standard requires 25 kWh/m2yr).

CARBON FIRST

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Embodied carbon: CLR completed Embodied carbon: CLR step-by-step Operational carbon: CLR completed Operational carbon: CLR step-by-step Operational carbon: existing house

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Figure 2. This graph gives annual emissions from space heating, embodied carbon and thermal comfort data across different phases of an existing house. For the first five years the house remains heated by gas, and is heated to 17.8 C. After five years a CLR step-bystep retrofit is done, including switching from gas to an air source heat pump, and a slight increase in thermal comfort to 18.1 C. The annual emissions decline for the next 17 years, as the heat pump benefits from decarbonising grid electricity. When the heat pump is due for replacement after 17 years (in year 22) a CarbonLite Retrofit is completed including deeper fabric measures and a smaller heat pump - and lifting the temperature to 20 C. For the full retrofit the figures are for external wall insulation (but internal wall insulation gives similar figures. Standard occupancy of 2.4 people per house was assumed.

healthier new and retrofitted low carbon buildings at a meaningful scale and pace.

Even without cultural and institutional inertia, and the dangerous and short-sighted delay from heavily vested interests such as

the fossil fuel industry, such change takes decades, and we have kicked the can down the road for too long. Hence, we are forced to rethink previously hard-won positions.”

CarbonLite Retrofit step-by-step: Heat pumps now for rapid decarbonisation The UK government is aiming to install 600,000 heat pumps a year from 2028, but

just 54,000 were installed in 2022. The heat pump rollout has been plagued by stories of high running costs and poorly designed systems, but some of this is simply malicious misinformation. The primary aim of the CarbonLite Retrofit step-by-step approach is to ensure heat pumps run efficiently, and do not increase energy bills, allowing fast and deep decarbonisation of a building’s space and water heating.

“Our housing stock modelling looked at space heating emissions from UK housing, and also incorporated upfront carbon emissions from building materials and

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3: Cumulative CO2e emission retrofit pathways: Figure 3: Figure Cumulative CO2e emission retrofit pathways: operational and embodied carbon operative and embodied carbon 220 200

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Full retrofit at A Full retrofit at B Step1 retrofit Business as usual

tonnes CO2e

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construction. It indicated that a smaller wave of the deeper CarbonLite retrofits along with

a much larger wave of CarbonLite step-bystep retrofits over the next few years would deliver a huge reduction in carbon emissions.

This even factored in the up-front carbon emissions from manufacturing the heat pumps,” says Simmonds.

“Also, critically important is to reduce the performance gap, which leads to homeowners’ energy bills and greenhouse gas emissions being higher than expected. Our step-by-step retrofit standard is designed to support installers, and ensure excellent heat pump design and installation quality in these low capital cost retrofits.”

When the heat pump is due for replacement after 17 years (in year 22) the CarbonLite Retrofit is completed including deeper fabric measures and a smaller heat pump and lifting the temperature to 20 C. For the full retrofit the figures are for external wall insulation (but internal wall insulation gives similar figures. Standard occupancy of 2.4 people per house was assumed.

The AECB stock model looks at electricity demand in the various scenarios in addition to carbon. It also considers peak heating demand on the national grid in winter. The model reports that a subsequent wave of CarbonLite Retrofits in about 20 years’ time would help to minimise peak demand on the electricity grid. This second wave would include more full retrofits as well as step-by-step retrofits that are further improved, following their whole house plans.

Both AECB large scale stock modelling and individual house type modelling show ‘bumps’ in greenhouse gas emissions at intervals due to the upfront carbon of retrofit, with larger bumps for deeper retrofits. But while important to factor in, these bumps are dwarfed over time compared to a business-asusual scenario (‘do nothing’).

Low bills, good health: The CarbonLite journey

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Figure 3. Cumulative greenhouse gas emissions from heating a typical UK semi-detached home. Business as Usual is a gas heated, unimproved home – which shows an unrelenting accumulation of greenhouse gas emissions into the atmosphere over 60 years, compared to dramatically reduced emissions from both the Step 1 and full CarbonLite retrofitted property. Retrofitted dwellings also deliver more comfortable, healthy and climate-resilient homes – key ‘non-energy’ benefits.Any emissions arising from decommissioning, stripping out, disassembly, deconstruction and demolition operations as well as from transport, processing and disposal of materials must be accounted for at the end of the reference study period, even if they do not necessarily happen at this time. For the purpose of this example, the standard 60 year reference period has been set to start at point A (for both full and step 1 retrofits). For the full retrofit starting at point B, we have brought forward end of life emissions so that they appear on the graph and figures are for external wall insulation, as for the previous graph. (Internal wall insulation using woodfibre gives an almost identical result after end of life emissions).

At the outset, a step-by-step retrofit aims to improve the building fabric just enough that the heat pump can operate at a flow temperature below 50 C – and ideally well below.

This keeps energy bills under control, but without the need for a disruptive, expensive deep retrofit now. To provide healthy indoor air, the standard also requires either mechanical ventilation with heat recovery, or simpler and cheaper mechanical extract ventilation.

For step-by-step certification, AECB certifiers must also ensure a longer term deep retrofit strategy is in place to further reduce energy use and operational emissions, and deliver other benefits such as improved comfort and health. This provides a clear long-term pathway to a net-zero carbon home or workplace, without creating a false choice between either ‘heatpumpification’ or ‘deep retrofit’.

“With this approach, you’re creating a ‘route map’ for each building, and a journey for the owners, and saying ‘let’s see how far along the journey we can bring your building’,” says Passive House Plus editor Jeff Colley, who is also chair of the Heat Pump Association of Ireland, and a board member of the Passive House Association of Ireland. “I think that’s really compelling — and with the same building physics of passive house behind it, the same rigour.”

Sally Godber of leading passive house certifier WARM sees CarbonLite Retrofit step-by-step as a great starting point on the retrofit journey.

“I’m really excited about this approach. In the void of funding and policy for retrofitting homes it’s a great solution for homeowners that want to do something to make a difference but can’t afford a full Enerphit. It’s well thought through and ensures that future measures aren’t compromised.”

CarbonLite Retrofit: a risk reductionbased approach to retrofit The full CarbonLite Retrofit standard requires a maximum space heating and cooling demand of 50 kWh/m2yr. That usually

necessitates a deep retrofit. A CarbonLite Retrofit may replace a gas boiler with a heat pump, but it also allows existing heating systems to be retained if necessary (for example if a new boiler was only recently installed).

“The standard offers a bit more flexibility than Enerphit,” says AECB certifier Paul Mallion. “It’s less prescriptive, therefore it can cope with smaller dwellings, older or more complicated ones that have a poor form factor.”

Passive house and AECB certifier Sarah Price, who helped to develop the CarbonLite Retrofit standard, echoes this. “I think it’s the best retrofit standard we have in the UK,” she says. “It’s pragmatic and is going to be applicable to many more buildings than Enerphit. I’ve done my fair share of Enerphit projects, and whilst they do have their place, and are fantastic projects, they are challenging and costly, especially in residential where residents have to, or want to, stay in their homes during the retrofit.”

Price particularly likes the way CarbonLite ensures the project team considers key risk factors like building condition, moisture risks, flooding, fire, and radon, which are not required for passive house certification.

Certifiers can allow some pre-approved exemptions from the 50 kWh/m2/yr rule — up to a max of 100 kWh/m2/yr — for specific reasons, such as building conservation, fire or moisture risk. By checking with a fellow certifier and logging their discussion (the ‘buddy system’), certifiers may also approve exemptions for other “compelling reasons”.

One such reason might be “if some deeper retrofit measures would emit significant amounts of upfront carbon”, Simmonds says.

In such an instance, the AECB encourages its certifiers to justify the exemption with a whole life carbon calculation. As the scheme builds up a body of evidence from the certification of more projects, the process should become simpler and less onerous, with more approaches becoming standardised or

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pre-approved.

CarbonLite New Build: Closing the performance gap CarbonLite New Build, previously called the AECB Building Standard, is aimed at new homes. It requires a space heating and cooling demand of 40 kWh/m2/yr. This standard is increasingly popular with housing associations, developers and local authorities seeking to provide healthy low energy dwellings. Recent projects include a large social housing estate in Castletown on the Isle of Man, numerous schemes across the south of England for Hastoe Housing Association, and an 88-home development by Stonewood Homes in Gloucestershire.

In Wales, social housing projects must achieve an energy performance certificate (EPC) of A, or be certified to an alternative low energy standard, to qualify for state funding. CarbonLite New Build is now accepted as such an alternative, following evidence submitted to the Welsh government

by Jonathan Davies and Jaime Moya, two AECB certifiers with Spring Design Consultancy in Bridgend.

Davies and Moya previously promoted passive house to housing associations, housebuilders and government, but say that most found the standard too much of a leap.

CarbonLite New Build, however, began to open more doors.

"We’ve been on a major outreach programme for the CarbonLite New Build standard to South Wales housing associations and local authorities,” says Moya, who is director of architecture at Spring. “We’re

finding that with the AECB standard, the reduction in energy demand, the tangible return for tenants, is there for all to see.”

Moya and Davies’s pitch includes modelling which shows that a typical semi-detached home, built to CarbonLite New Build and with an EPC of B, can achieve half the space heating bills of the same house built to a conventional EPC A specification.

"The CarbonLite New Build standard is attractive, and it’s upskilling the supply chain to a level it can deliver now, so we can work towards higher levels of performance, towards passive house as a new building standard for Wales,” Moya says. “We firmly believe as architects and passive house designers, that it’s up to us to try to make this happen.”

Passive house in new terrain Ultimately, the revised CarbonLite Retrofit standard takes passive house into new terrain, applying it to ‘heatpumpified’ & lightly retrofitted buildings to leverage the decarbonising UK electricity grid — arguably without compromising the rigorous building physics of passive house, and without compromising future deep retrofits.

Sarah Price, however, is keen to see the core focus remain on deep retrofit. “Yes, rapid decarbonisation is the urgent goal, we need to electrify heating, we need to put heat pumps in,” she acknowledges. “But equally for me, we have the worst housing stock in Europe.

We have excess summer deaths, excess winter deaths. We could be doing so much better with our houses, and I think we need to be sending that message out saying look, fabric retrofit has many and varied benefits if we get

(below) A semi-detached house in Lancaster retrofitted by Coldproof may be the first project to take the new CarbonLite step-by-step approach. 1 Existing double glazed windows were retained, existing cavity was pumped; 2 the outdoor unit of the air source heat pump; 3 airtightness membrane retrofitted across stud wall and ductwork void created; 4 underfloor heating installed; 5 internal woodfibre insulation was added.

CARBON FIRST

it right.”

The CarbonLite standards are still in their infancy and their applicability and effectiveness in delivering better, low carbon, low energy buildings will continue to evolve as the AECB reflects on a growing amount of real-world feedback. “It’s an experiment of sorts,” says Andrew Simmonds, “but a necessary and urgent one”.

“We are looking to help drive up minimum standards, so that the resources we do have — including the time people have available, the financial capital and materials — are used in a way that rapidly reduces greenhouse gas emissions and improves the health and wellbeing of people living in their homes.”

For more see www.aecb.net n

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Marketplace News Tackling carbon emissions with Passive EcoWall

C

arbon emissions originating from the construction and operation of buildings in the UK constitute a sizeable portion of the country’s overall emissions, amounting to 40 per cent. According to The UK Green Building Council (UKGBC), embodied carbon from the construction and refurbishment of buildings is directly responsible for around 20 per cent of built environment emissions and based on current figures, this is likely to be over half of the overall built environment emissions by 2035. These embodied emissions are often regarded as the “carbon blind spot” within the construction industry.

To achieve the UK’s climate ambitions, it is imperative to address both operational and

embodied carbon emissions in the built environment. This entails adopting strategies such as optimising existing buildings, prioritising low carbon materials and designs, and employing energy efficient construction methods.

In response to this challenge, Ecological Building Systems has introduced the Passive EcoWall building solution for new timber frame buildings, which offers exceptional thermal efficiency, exceeding nZEB requirements, and incorporating materials with lower, or even carbon neutral emissions. Passive EcoWall follows proven passive house principles and includes elements like Gutex wood fibre natural insulation, Finsa Superpan VapourStop E-Z airtight racking boards, and the Pro Clima intelligent airtightness system. Several certified passive homes and modular buildings in Ireland and the UK have demonstrated reduced energy consumption and increased comfort through this system.

To exemplify this, a timber frame manufacturer, Lidan Designs, adopted the Passive EcoWall concept for a 200 m² school building in Cork, Ireland, which recently featured in Passive House Plus. This achieved a remarkable embodied carbon score of 249.3 kg CO₂e/m²,

surpassing targets set by the Royal Institute of British Architects (RIBA) and the 2030 Climate Challenge. The building also received an A+ rating on the Low Energy Transformation Initiative (LETI) scale for its up-front and whole life carbon emissions and hits passive house airtightness levels. Large scale projects like this demonstrate the feasibility of using natural materials, with lower embodied carbon, for high-performance modular buildings in the UK. Passive EcoWall offers specifiers and designers a comprehensive, unique, “off the shelf” product specification for timber frame construction. The system is supplied with clear, comprehensive detailed drawings focusing on thermal continuity and optimum airtightness and windtightness details. Adopting such construction techniques and natural materials ensures industry can effectively address not only operational emissions, but also embodied emissions, thus playing a pivotal role in the UK’s sustainable building future. • (left) The Passive EcoWall system combines excellent thermal performance and embodied carbon properties.

Zehnder launches MVHR system for tight spaces

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ehnder Group UK has launched the Zehnder ComfoAir Flex – a mechanical ventilation system with heat recovery (MVHR) specifically designed for tight spaces and challenging installation environments.

Small in size and narrow enough to be ceiling mounted, the new ComfoAir Flex is a compact solution for improving indoor air quality in urban apartments, small houses and student accommodation, where space is at a premium.

Despite its compact size, the ComfoAir Flex boasts a heat recovery efficiency rate of 96 per cent, ensuring minimal heat loss and contributing to substantial energy savings.

The new system also performs to current and future EPB requirements at energy class A+.

Available in two sizes for properties up to 200 m2 and 250 m2, ComfoAir Flex is adaptable to a wide scope of buildings, due to the system’s ceiling-mounted design and four, 45-degree turnable bends for versatile duct installation. Each air connection can be individually turned to connect to a duct inline with the unit or rotated 90 degrees.

This allows flexibility for developers to de-

sign projects with less restrictions.

Zehnder Group UK commercial director Stuart Smith said: “The ComfoAir Flex brings a potential revolution to the UK construction industry. Its unique attributes could significantly alter the industry’s approach to environmental sustainability and occupant comfort, addressing the critical need for energy-efficient, space-conscious buildings in the urban landscape.

Smith said the new system exemplified Zehnder’s commitment to the passive house standard and has been well received on the continent.

“The introduction of the ComfoAir Flex into the European market was met with enthusiasm, and we anticipate similar success in the UK. The product has been appreciated for its energy efficiency, health benefits, user-friendliness, and adaptability in various installation scenarios. It’s going to be a game-changer in providing better indoor air quality for smaller living spaces.”

The ComfoAir Flex features upgradable high-grade filters and 100 per cent full and filtered modulating summer bypass to maintain a continuous flow of fresh, filtered

air, and significantly enhanced conditions to support occupant comfort and health.

The unit’s software allows for left or righthand configuration, adding an element of adaptability to its installation. Furthermore, its Wi-Fi enabled app control as standard gives users complete control over their indoor climate, contributing to an enhanced user experience.

The system can also be integrated into Smart Home via KNX and ventilate on demand thanks to the CO2 sensor. • (below) The ceiling-mounted design of the ComfoAir Flex.

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MARKETPLACE

PASSIVE HOUSE+

Partel launches paper-based membranes G

alway-based sustainable building product supplier Partel has launched two new paper-based membrane products, Izoperm Plus Eco and Vara Plus Eco. The company describes Izoperm Plus Eco as a paper-based sustainable vapour control layer membrane, and Vara Plus Eco as a paper-based smart ecological vapour control layer membrane.

The products are intended to provide a solution for internal applications, improving indoor air quality and ensuring optimum protection against humidity in the building structure, while helping minimise heat loss.

Developed to enhance the sustainable features of Partel’s Vara and Izoperm vapour control layer membranes, the company is in the process of obtaining Environmental Product Declarations (EPDs) to quantify their ecological impacts – and expects to be able to demonstrate how the use of the products will help achieve embodied carbon reductions.

Composed of up to 60 per cent renewable FSC-certified paper, the products contain a three-layer fabric mesh reinforcement for

high tear-resistance, combining strength, airtightness and moisture management.

Compliant with the stringent requirements of the Emicode eco label system, Izoperm Plus Eco meets the Ecolabel Emicode EC1 PLUS. Driving sustainability for reduced carbon emissions where it is primarily used on internal walls, ceilings, and floors, it prevents heat loss with an SD value of 20m for achieving optimal thermal insulation. Izoperm Plus Eco is designed to be compatible with all conventional building systems and insulations.

Vara Plus Eco consists of up to 62 per cent of FSC-certified paper and has been designed to maintain the optimum airtightness in the building envelope, while providing active moisture control via hygro-variable technology. Partel said the product can be utilised in the most demanding of conditions as an inner airtight membrane and as a vapour control layer for externally vapour-open build-ups, ensuring compatibility with all conventional insulations. • (right) Izoperm Plus Eco and Vara Plus Eco, Partel’s new paper-based membranes.

Beattie Passive appoints self-build manager

(above) Simon Clarke, Beattie Passive’s newly appointed client solutions manager.

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assive house pioneer and offsite modular construction specialist Beattie Passive is delighted to announce the appointment of Simon Clarke to the newly created role of client solutions manager.

As a prominent member of the Passivhaus Trust, the Association of Environment Conscious Building (AECB), and the Good Homes Alliance, Beattie Passive has been at the forefront of sustainable and energy efficient design for over a decade. Over

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the past 10 years, the firm has built almost 500 properties to the passive house standard using its proprietary, patented and passive house certified build system.

The company said Clarke’s appointment underscores Beattie Passive’s continued commitment to delivering innovative solutions for its self-build and custom-build clients, and that his experience and expertise make him a valuable addition to the Beattie Passive team. An experienced project manager, Simon is poised to lead the company’s self-build division to new heights.

Simon expressed his enthusiasm for the role: “I am thrilled to join Beattie Passive and head up the self-build division,” he said. “This company’s commitment to sustainable construction aligns perfectly with my own passion for eco-friendly building practices. Beattie Passive has a strong track record of passive house projects and I’m eager to contribute to the company’s continued growth and development in the selfbuild market.”

New bid manager Meanwhile, the company has appointed Graeme Robson to the newly created role of bid manager. This strategic appointment follows the firm’s recent success in securing positions on three major offsite con-

struction frameworks, including a Crown Commercial Service offsite construction solutions framework for residential and energy upgrades, The Offsite Homes Alliance (OSHA) National Modular Construction Framework, and the LHC Modern Methods of Construction (MMC) of New Homes (NH3) Framework.

Graeme will be responsible for writing pre-qualification questionnaires and tenders for public sector new build and retrofit projects. “I’ve worked as a bid writer for over twenty years, primarily in facilities management, but more recently in groundworks,” said Graeme. “I have a keen interest in sustainability, so I’m looking forward to working for a company that promotes sustainable building practices. Beattie Passive ticks all the boxes for public sector procurement, so that certainly makes my job a little bit easier,” he added.

Ron Beattie, founder and managing director of Beattie Passive, said: “Bids play a key role in our business development and we have a very strong proposition in terms of energy efficiency, sustainability and social value. I’m absolutely delighted that we’ve appointed someone of Graeme’s calibre to provide in-house bid support as we look to build on the success of our award-winning, net zero-rated passive house projects.” •

PASSIVE HOUSE+

MARKETPLACE

Unilin launches embodied carbon report

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eading insulation manufacturer Unilin has produced a report on calculating and reducing embodied carbon while using the company’s products.

The report, Reduce by Design: Action on Embodied Carbon, provides an overview of the process and calculation of embodied carbon in a study of house types.

Multidisciplinary consultancy XCO2 was commissioned to carry out life cycle assessments (LCAs) for four different dwelling types – including typical examples of a detached house, mid-terraced house, semi-detached house, and apartment – built using typical material specifications, to see if they could meet the embodied carbon targets set by organisations including RIBA, LETI and the Future Homes Hub. The analysis was cradle to grave, covering modules A1-C4, excluding B6-B7, which cover operational energy and water use, and which are customarily reported separately in building LCAs in the UK and Ireland.

With a scope including all elements of the building excluding external works, and relying on products with EPDs where possible, baseline case scenarios were established, along with improved specifications in each case, including measures such as substituting 70 per cent of cement with GGBS in the concrete slab, switching to a calcium sulphate screed, and swapping concrete roof tiles for natural slate – and a shift from generic PIR to Unilin’s ECO360 PIR. Three options for heating systems and domestic hot water were included – including an air source heat pump-based approach, a passive solar-based design with heat recovery ventilation and electric water heater, and a direct electric system. In the case of the heat pump baseline and improved cases were included, depending on the global warming potential of the refrigerant. The baseline case included a heat pump with 1.3 kg of R410A, a refrigerant with a global warming potential (GWP) of 2,088, meaning each kilo is equivalent to 2,088 kg of CO2 (expressed as 2,088 kg CO2e). The improved case included 3 kg of R32, which has a GWP of 675, dropping the embodied carbon total from 48 to 36 kg CO2e/m2.

In all four house types, the improved specifications met the RIBA, Future Homes Hub and LETI targets. In one case – the mid-terraced house, the air source heat pump option brought the building over the target.

with the integration of bio-based polyols, more than a 50 per cent reduction in packaging waste, halogen-free formulation – and an impressive thermal conductivity of 0.020 W/Mk. “The ECO360 insulation strategy is a key innovation in our endeavours,” the company said, in a foreword to the embodied carbon report. “ECO360 is evidence of our commitment to continually review and improve the sustainable credentials of our product offering and services, as far as technical advances in manufacturing and circularity allow.”

“The aim is to gauge the impact of our improving Environmental Product Declarations (EPDs) on a building’s life cycle analysis,” the company said. “We worked with industry bodies and software providers to educate our own team in the conventions and methods related to embodied carbon measurement. This is only the start of a journey.”

Unilin said that strong alliances and co-operation between manufacturers, the supply chain, designers, and contractors will be re-

quired to help address the climate crisis. “All of the manufacturers we engaged with in the preparation of this report are fully committed to improving their own EPDs along with the continued decarbonising of the grid, and so results for embodied carbon shown will continue to reduce,” the company said. “We hope this report and accompanying CPD learning will encourage information sharing and engagement with the subject.”

“In line with our sustainability pledge, we are committed to achieving lower embodied carbon in builds.”

“It has been independently proven that with clever design using high-performance Unilin insulation, we can reduce embodied carbon levels in construction which meet and can exceed targets set by Future Home Standard 2025, LETI and the RIAI 2030 Climate Challenge.”

To find out more, download Unilin’s embodied carbon report at unilininsulation. co.uk/embodied-carbon/ •

Unilin aims for zero carbon In 2021 Unilin Group launched its sustainability pledge, including an aim to become a net zero carbon operation by 2030. As part of the company’s One Home sustainability policy, Unilin pledged to make environmental improvements in all aspects of its operation including the manufacture of insulation products. The company launched its EC0360 insulation in 2021, introducing several environmental improvements to PIR insulation

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D R TO B Y C A M B R AY

COLUMN

A new energy policy: give to the frugal, take from the profligate Should we look to Robin Hood to help transform energy use in buildings? New proposed reforms to how energy is priced could hold the key to discouraging excessive energy use, stimulating retrofit and driving down carbon emissions, argues Toby Cambray.

U

K politics is in a sorry state at the moment; not only has the current administration lurched alarmingly to the right, but it has also poisoned our discourse with the three Ps of populism, polarisation and post-truth. Recent by-elections do however indicate the electorate are ready for change which in my echo chamber at least, is to be celebrated. It is therefore frustrating that we are not seeing more bold proposals from the presumed government in waiting, although this does make strategic sense. At the risk of revealing my second favourite* podcast, Keir Starmer is carefully carrying the Ming vase of victory across the marble floor that is 2024. It’s straight forward to make it to the other side, just don’t do anything silly, like a radical consumer energy policy.

Fortunately, I have no intention of attaining high office, and no qualms about sharing with you some thoughts on what might be done to address fuel poverty, energy security and climate change simultaneously.

In March, the New Economics Foundation (NEF) published a proposal for a policy which in my opinion deserves a lot more press than it has thus far received: a National Energy Guarantee. The concept is relatively simple, and there are many variations on the theme, so it can be refined to get the best outcomes.

The idea is proposed as a counterpoint to the existing policy: a subsidy that was introduced to soften the blow of the dramatic price cap increases we saw in the autumn of 2022, which became necessary in light of international price rises. This blanket subsidy missed several opportunities that the NEF proposals have the potential to address.

The proposal is that up to some basic level of energy consumption, the cost per kWh is either zero or a small amount. Above this, prices per kWh are higher. The amount of free or low-cost energy is set at a level that represents a minimum necessary for a basic standard of living; extravagant energy use is

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therefore costly. A refinement is the addition of one or more intermediate levels, or perhaps even a simple continuous function, so that the increases in cost per kWh is graduated to some extent. In my version, at the top end there is no energy price cap.

This is more equitable and sets up more powerful incentives to avoid unnecessary energy consumption, without incentivising inappropriate reductions in energy use, in particular relating to avoiding heating and under-ventilating. It therefore tilts the playing field in favour of investment in retrofit and other energy saving measures, and consequently carbon emissions reductions.

This is obviously an overtly progressive policy that I’m sure will be dismissed out of hand by the current administration; but structured the right way it need not cost the treasury anything, let alone the £5.5 billion that the current blanket approach did, because revenue from the upper tiers funds the free/low cost lower tiers. Careful setting of breakpoints and prices would mean the average consumer sees little or no net change in their cost, because their higher tier usage funds all their consumption. If Robin Hood dealt in electrons he would be taking from the profligate and giving to the frugal.

As with building physics there are of course unintended consequences to be mindful of.

One is that some individuals have needs that dictate high energy use, such as heating to higher temperatures or large volumes of laundry for health reasons. People in such circumstances must be provided with appropriate support; several vouchers and benefits already exist and could be re-calibrated or integrated with the policy via bespoke consumption thresholds, for example.

A second issue is potentially trickier and relates to the need to move towards more flexible models of energy (specifically electricity) consumption, the icon of which is the Octopus Agile tariff, effectively allowing consumers to purchase on the half hour market (and occasionally even ‘sell’ their

Up to a basic consumption level, the cost of energy would be zero or a small amount consumption). These two types of tariffs can coexist as happily as they do currently, but a key rationale with flexible tariffs is that they implicitly link our consumption less with the number of kWh, and more with the infrastructure needed to deliver them.

As we move towards a system dominated by renewables, heat pumps and EVs, the ability to match demand to supply, (not the other way around as is currently the case) will become increasingly important, and the National Energy Guarantee in its current form does not directly address this.

Nonetheless, it would be relatively easily implementable via smart meters, and an improvement on the current policies with regards to equality and incentivisation of energy sufficiency. You can read the NEF proposal in full here: neweconomics.org/campaigns /national-energy-guarantee n

*Favourite isn’t quite the right word for receiving measured and informed analysis from some chaps who are quite so obviously delighted with their own cleverness, and I’m not talking about Jeff, Dan or Alex at Zero Ambitions Podcast.

Toby Cambray is a founding director at GreenGauge and leads the building physics team. He is an engineer intrigued by how buildings work or fail, and uses a variety of methods to understand these processes.

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