Passive House Plus (Sustainable building) issue 36 IRL

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NEW ENGLAND REBEL Bandon passive house with Vermont roots


Do your walls behave like a Jaffa Cake?

What the humble snack can tell us about moisture in buildings

Thinking inside the box

Phibsborough semi retrofitted as a house within a house

Up with the Lark

Bucks passive house ‘plus’ manifests a new energy vision

Issue 36 €6.95 IRISH EDITION

Why it’s time to get serious about school ventilation



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SOLAR GAIN & the Irish climate Considering the ever-improving window energy efficiency standards across Europe, it is important to understand the various contributing parameters and their impact. What it ultimately comes down to is finding the right balance between U-value and solar gain, while understanding their significance in determining the actual thermal performance of glazing.


efore discussing the principles and importance of each parameter, it is worth briefly noting what they mean in simple terms. U-value quantifies the amount of energy – specifically heat energy – lost through the window, while g-value (solar gain) represents a potential amount of energy that can be captured by sunlight passing through a window in specific circumstances. Consider this crucial point for a moment: while the heat loss represented by U-value is certain, the solar gain represented by g-value is only potential and dependent on conditions. A window with a U-value of 0.9 W/m²K will lose such amount of heat regardless of its environment. It does not matter which part of the house the window

is in, at what height or which direction it is facing. A solar gain of 60% represents energy that we may potentially capture if there is enough sunlight passing through the window for a specific period of time. In reality, even south-facing windows will not achieve the theoretical energy gains in a country like Ireland during winter, where such gains would actually be beneficial. Heat loss occurs during every hour of every day, in a year that is 8,760 hours. Therefore, it is certainly worth our best efforts to minimise it. Solar gain, however, can only be considered to contribute to a building’s energy balance when the sun shines through the window. With an average of around 1,200 hours of sunlight per year1, Ireland can take little


advantage of the sun’s natural supply of heat energy. During the 6-month heating season (4,380h), considering average daylight hours, we can at most hope for around 380h of direct sunlight. If we assume that the days are half as sunny as during the other 6 months, we arrive at 190h. This is, theoretically, the amount of time that solar gain may contribute to a home’s internal temperature – against 4,380h that U-value has a definite effect on the indoor climate. U-value is constant, while solar gain is inconsistent. What we mean by this, in simple language, is that it is always good to have well insulated windows, and indeed other parts of the building – this will keep you warm in the winter and cool in the summer. On the other hand, solar gain in winter would be valuable (albeit an unrealistic expectation during an Irish winter), while solar gain in the summer, where it is far more likely, can actually cause the building to overheat. Some professionals believe in the benefit of sacrificing U-value performance in return for better solar gain, and often specify double glazed windows on the south facing parts of the building. Doing this will result in compromising a certain heat retention measure in pursuit of higher potential of heat generation from an unreliable source. Below is a sample calculation of the trade off involved in downgrading from a high quality triple-glazed unit to a standard double-glazed one. Oknoplast 4/18/4/16/4 triple-glazed unit g-value = 53% U-value = 0.5 W/m²K Typical double-glazed unit g-value = 64% (11% gain) U-value = 1.1 W/m²K (120% loss) Practically speaking, conditions to make solar gain relevant in Ireland are rarely met. In conclusion, solar gain is a sound engineering concept, but its influence is greatly diminished by the nature of the Irish climate. Meanwhile, U-value is a parameter whose significance remains unaffected.

Source: ResearchGate

1 Attached map of Europe shows various zones for annual hours of sunshine across the continent. According to Met Éireann, the average figures for Ireland fall between 1,100h and 1,300h.

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Jeff Colley

Deputy Editor

Lenny Antonelli


John Hearne


Kate de Selincourt


John Cradden

Reader Reponse / IT

Dudley Colley


Oisin Hart

Art Director

Lauren Colley


Aoife O’Hara |


Justin Bere bere:architects Toby Cambray Greengauge Building Energy Consultants Marion Jammet Irish Green Building Council Anthea Lacchia journalist John Morehead Wain Morehead Architects Marc O’Riain doctor of architecture Mel Reynolds architect Peter Rickaby energy & sustainability consultant David W Smith journalist


editor’s letter W

hat an inauspicious start to a decade 2020 has proven to be. It is customary at this time of year to reflect on what has been and to resolve to do better in the coming year. There are some reasons for cautious optimism. The sense of relief at Trump’s defeat is palpable, but we must not get too giddy. His defenestration from 1600 Pennsylvania Avenue is a great relief, but no more than that. It’s like the relief you might feel after watching your football team end a run of brutal defeats. Sure, you appreciate the fact of not being beaten anymore. But how much damage has already been done? So while it will be a tonic to see America come back into the fold and rejoin international efforts to tackle the climate emergency, there is no getting away from the fact that we have lost four years in a fight of existential proportions, for our and the vast majority of other species. So awful has Trump’s tenure been — along with the similarly fact-averse, jingoistic rhetoric of other governments and political phenomena closer to home — that the prospect of returning to the familiar norms of the recent past is comforting. But I worry. We are facing environmental crises that will not go away and will in fact grow in severity and scale. All we can do is attempt to minimise the extent of the damage and prepare for it as best we can. We cannot just vote these problems out and wipe the slate clean. Environmental breakdown will be an issue, and an issue that becomes ever more central, for the rest of our lives and beyond. Then there’s Covid. From an environmental perspective, Covid hasn’t been entirely negative, as demonstrated by the projected record drop of 7 per cent in global emissions in 2020, in very large part due to the pandemic. But, as with the political situation,

ISSUE 36 there is an overwhelming public desire to get back to normal, leading to the very real risk of a rebound effect. Of course, the good news about vaccines gives us reason to be hopeful that we may find a way out of the pandemic, but it will still take some time for the virus to be brought fully under control, if indeed that is even possible. It’s incumbent on us to learn from this experience, and to plan, invest and reorganise our societies to provide us with the flexibility and resilience to adapt to a world that may or may not have resolved the Covid crisis, that may be at risk of future pandemics, and that faces the inevitability of increasingly extreme weather and disruptive climate conditions. The human race has the capacity for extraordinary ingenuity and adaptability, though we tend to demonstrate this in response to immediate and easily comprehensible threats, rather than the much harder to process scientific warnings based on aggregated measurements and computer simulations that confront us with climate breakdown. Never waste a good crisis, Churchill said. The challenges we endured and lessons we learned in 2020 must enable us to become more resilient and to stop pouring petrol on the fires we have lit on an increasingly uncertain world. Listening to the shocking evidence emerging from the Grenfell Enquiry, we should take the time to reflect on how we conduct ourselves in business and life. I speak both in a personal and professional capacity, but this point applies to us all. We must not put the interests of short term profit and our own immediate economic concerns in front of the public good and the natural world which sustains us all. Regards, The editor


GPS Colour Graphics | +44 (0) 28 9070 2020


Bandon passive house Photo by f22 Photography Publisher’s circulation statement: 9,000 copies of Passive House Plus (Irish edition) are printed and distributed to the leading figures involved in sustainable building in Ireland including architects; consulting; m&e and building services engineers; developers; builders; energy auditors; renewable energy companies; environmental consultants; county, city and town councillors; key local authority personnel; and to newsagents nationwide via Easons. Disclaimer: The opinions expressed in Passive House Plus are those of the authors and do not necessarily reflect the views of the publishers.

ABC Certified Average Net Circulation of 6,417 for the period 01/07/18 to 30/06/19


Passive House Plus is an official partner magazine of the International Passive House Association. Passive House Plus (Irish edition) is an official magazine of the Passive House Association of Ireland.

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COLUMN Mel Reynolds analyses the state’s surprising reluctance to build its own homes.

INTERNATIONAL This issue features a passive house ‘plus’ certified three-storey office building in Strasbourg, France.




The effect of NZEB regulations on new build specs starts to become apparent, a new campaign is launched to reduce the whole life cycle carbon footprint of buildings, and the latest from the Grenfell Tower Inquiry.

COMMENT Dr Marc O’Riain looks at what might be considered an early prototype in the development of passive houses: the 1974 Philips Experimental House; and Dr Peter Rickaby writes on the varied and complex challenges of retrofitting older buildings.

CASE STUDIES New England rebel Cork passive house with Vermont roots

A stunning new passive house in Cork breaks the conventions of passive house form with a design that manages to be both dramatic yet discreet at the same time, inspired by a US project to contort itself beautifully into its steeply sloping site.

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Thinking inside the box Victorian semi retrofitted as a house within a house



Facing the challenge of how to bring a Victorian home with damp old brick walls up to a modern low energy standard, architect Brendan O’Connor deployed an innovative solution: build entirely new and superinsulated timber frame walls within the old structure.


Inside the UK’s largest passive school Harris Academy Sutton delivers top class comfort & superb air quality for pupils

Up with the lark Buckinghamshire passive house ‘plus’ manifests a new energy vision

Lark Rise is an elegant new passive house in rural Buckinghamshire designed by bere:architects, but it is more than ‘just’ a passive house. Because it produces and stores so much of its own energy through onsite solar power, it is a certified passive house ‘plus’, and its architect Justin Bere explains how dwellings like this can play a key role in decarbonising our economies and societies in the coming decades.

INSIGHT Breathing room Why it’s time to get serious about classroom ventilation

Proper ventilation has been recognised as an important quality for school buildings at least since the Victorian era. But, in the current pandemic, have we lost sight of the role of ventilation?


With a decade of experience designing primary schools to the passive house standard under their belt, Architype have now designed the UK’s first passive secondary school — and all of the evidence suggests there is no better way to ensure a healthy, comfortable environment that is supremely conducive to learning.



Basements in low energy buildings Key issues to avoid moisture and heating problems

Where basements are present in low energy buildings, they can prove a weak spot without particular care and attention, as Passive House Association of Ireland board member John Morehead of Wain Morehead Architects Ltd explains.



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

Do your walls behave like a Jaffa Cake?

Toby Cambray writes on the many lessons that the inimitable biscuit cake can teach us about how building materials deal with moisture.

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Is affordable housing a policy blind spot? Dublin City Council built just 45 social housing units in 2019. In his latest column, Mel Reynolds analyses the state’s surprising reluctance to build its own homes.


ndustry reports have suggested modest house price falls in 2020. Private equity fund purchases of entire schemes have resumed and land values continue to be bid up, albeit with fewer transactions. Ireland’s ‘low supply / high price equilibrium’ housing market appears impervious even to a global pandemic. When the shadow of Covid-19 begins to fade next year imbalances in the housing sector will again become apparent. Official policy inertia surrounding affordable housing makes the problem appear insurmountable. However, it is not. The best metric to illustrate demand for affordable and social housing is the combined housing list and Housing Assistance Payment (HAP) lists. These show how many households have been waiting for social housing for

(PPP), which I discussed in this column in issue 32 of Passive House Plus). Recent figures from both the Dáil and the Department of Public Expenditure and Reform confirm that the state can develop directly at half the cost of buying new homes. The total figure for local authority builds in 2019 was 1,088, and just 228 were built directly by the four Dublin local authorities. This figure is less than in 2018 when the state completed 1,238 local authority builds. Remarkably Dublin local authorities built 232 social houses in 2017, more than in 2019. The example set by Dublin City Council illustrates the gulf between demand and continued official inertia. In Dublin City there is a social and affordable demand of more than 20,000 households while in 2019 the City Council’s

Remarkably, County Dublin local authority build levels are falling. years and how many households are currently receiving rent assistance in the private rental sector. With the exception of South Dublin, availing of HAP means losing your place on the housing list, so a combination of both lists gives a good indication of households on more modest incomes (less than €18,000 per annum) that need social and affordable housing. The total nationwide demand figure as of May was more than 124,000. In County Dublin, the location of greatest housing need, the demand figure is 39,000. The best metric to highlight state intent, where the state controls the entire process — owns land, can get planning permission quickly, avail of ultra-cheap finance and develop housing directly — is local authority builds, where the state acts as developer. There are other forms of procurement, but many take years and are far more expensive (such as the O’Devaney public private partnership

build output was just 45 units. Of this total, 24 were refurbished apartments at Priory Hall, rebuilt for €141,000 per unit and not new builds at all. (Nineteen of the remaining 21 builds were so-called ‘rapid’ units where DCC paid a premium of €384,000 per unit, more than 25% above the average cost in County Dublin of standard local authority homes built in 2019.) In contrast, Dublin City Council owns 112 hectares of zoned residential land with capacity for well over 10,000 homes. They are currently utilising just 0.01% of this capacity. The scale of local authority underperformance across the board suggests systemic issues with official policy and the Department of Housing. Dublin City Council has been in the news for the failure to get its proposed PPP regeneration scheme at Oscar Traynor Road off the ground. Councillors voted down proposals to hand over a large tract of land owned by Dublin City Council to a private developer.

CO DUBLIN: Housing demand (social and affordable) Housing List (110619)

Total Active HAP Tenancies (180520)


D/L Rathdown

Local authority








South Dublin




Dublin City








Table: Co Dublin Housing Demand 2020

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The deal was broadly similar to the one at O’Devaney Gardens, where a portion of units will be made available to the state to purchase as social housing and to be heavily subsidised as affordable housing for sale to those on more modest incomes. Back in the early noughties, PPPs entailed the state handing over a site to a developer and getting units back for free as social housing. These days the site is handed over and the state ends up buying back social housing while paying a premium. PPP deals of this nature are very complex, take years to get going and are remarkably poor value for the taxpayer. Government reliance on turnkey purchases, where the state and approved housing bodies (AHBs) buy directly from the private market, has increased to 25% of all new homes built nationwide in 2019. Government policy to purchase at this scale rather than build directly has become a systemic risk to the new housing sector. Where the state is renting, in areas of high demand such as County Dublin, the cost is more than double the cost to build directly. In Dún Laoghaire-Rathdown, the average annual cost to rent a Part V dwelling had doubled from 2017 to €28,310 per year in 2019. The state is increasing social housing stock by buying from the private sector. In areas of high demand this is twice the cost of direct build on state land. When not purchasing, the state is subsidising thousands of private tenancies and driving rent inflation. Excluding other semi-state bodies, between NAMA and local authorities, the state controls enough land to build more than 70,000 dwellings. In County Dublin the state controls 50% of all zoned residential land. Remarkably, County Dublin local authority build levels are falling. It would appear that the government’s continued unwillingness to support local authority direct procurement not only defies logic but is a massive cost to taxpayers. n A fully referenced version of this article is online at Mel Reynolds is a registered architect with more than 25 years of experience in project management, conservation, urban design and developer-led housing. He is also a certified passive house designer.



© GettyI mages


BXC HPS: THE NEW HUMIDITY SENSITIVE EXTRACT WITH A CONTROL INDICATOR The BXC hps is especially adapted to meet the Technical Guidance Documents (TGD) Part F 2019 of the new Building Regulations in Ireland. From the 1st of November 2020, under the new building regulations in Ireland, a control indicator should indicate that the system is running correctly. A light saying there is power to the device or an app on someone’s phone is unlikely to meet the requirement.

In addition to modulating the airflow according to humidity and in line with these new regulations, Aereco’s BXC hps indicates correct running performance of the system and alerts the homeowner of a fault.

For more information: air on demand


IN BRIEF Building: Three-storey office building Location: Strasbourg, France Building method: Concrete shell with external insulation Standard: Passive House Plus certified






Photos by Luc Boegly

n old industrial building had sat derelict on the banks of the river Ill in Strasbourg, France since the late 1990s. It last served as a coffee roastery but remained empty until the engineering practice Solares Bauen came along and purchased it, with an eye towards renovation. The firm envisioned the building becoming home to their thermal and environmental modelling team and wanted to preserve the existing structure to create an exemplar of sustainable building. Work got underway, but when the original building’s walls were investigated, it was discovered that they were in too poor a condition to be preserved. Work stopped for several months while every effort was made to save them, but in the end the original building had to be demolished. So, the team — led by local architecture practice Richter & Associates — went back to the drawing board, preserving and working up from the original foundations, which were reused. New concrete walls were fitted out externally with I-beams, which were insulated with cellulose. The new roof is a concrete slab too, and while all this concrete might not be the most low carbon choice, Solares Bauen were keen on a heavyweight structure with thermal mass to smooth out temperature peaks in summer. And not surprisingly, given the nature of their work, Solares Bauen also carried out extensive modelling of summer comfort in the building, considering the thermal mass of the structure, solar gain, shading and ventilation. Shading is manually adjustable through the seasons, and all windows openable too (one of the lesser known requirements of the passive house standard is that it generally requires one openable window per room). The finished building not only meets the passive house standard, it is also passive house ‘plus’ certified because of its 18 kWp solar photovoltaic array. The reuse of the existing foundation, plus the emphasis on natural and recycled materials elsewhere also earn sustainability credits, as does the fact the office is easily accessible on foot, bike or tram. Meanwhile space heating and cooling is provided by a water-to-water heat pump, drawing on groundwater on the site. With capacity for up to 50 employees, the finished building is a beautiful piece of architecture, its simple and slightly austere exterior drawing on the industrial heritage of the site, its dark timber cladding merging into the surrounding trees. Inside, though, the building opens out into a light-filled and airy workspace that shows off its concrete structure. The offices neatly walk the tightrope between being too closed and too open plan, using timber fins and internal glazing to break up the spaces without making them cloistered.

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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


We must look towards the future of the built environment with a vision to enforce environmental development As a significant consumer of energy, the built environment must therefore be a focus for energy saving efforts. It is our responsibility as contributors of the built environment to resolve a more sustainable and socially responsible way of building. We operate with the purpose of carbon reduction in both the creation and operation of our buildings - ensuring our buildings perform as intended, with the intention to reduce energy expenditure. The building fabric forms the basis of your buildings performance, lasts the entirety of the building’s lifecycle and requires zero maintenance and as such should be a focus for our future efforts. We are taking pride in our buildings, our intentions and our impact. e. | t. 0330 133 2511




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NZEB’S EFFECT ON NEW HOME SPECS EMERGES Heat pumps dominate & mechanical ventilation grows, but compliance risks emerge


arly signs have emerged of how the construction industry is meeting the NZEB standard for new homes – with heat pumps becoming near ubiquitous, mechanical ventilation systems starting to dominate, and fabric standards improving. Analysis by Passive House Plus of data from the National BER Research Tool showed that 1,862 final BERs for new homes were built to Technical Guidance Document L 2019 for the year up to 8 December. The analysis compared new homes built to the 2019 version of TGD L against new homes built between 2018-2020 to the previous (2011) version of TGD L. Transitional arrangements in TGD L mean that some homes built to the 2011 requirements are still being completed. In total, 91.8 per cent of TGD L 2019 homes are A2 rated, 6.7 per cent are A3s, and 1.2 per cent are A1s. The average primary energy score is 41 kWh/m2/yr, compared to an average of 51.3 kWh/m2/yr for new homes built to the previous regulations. The most significant change in specifications in the shift from 2011 to 2019 TGD L may lie in the space heating systems – 95.1 per cent of new homes built so far to 2019 TGD L feature heat pumps, almost doubling their market share from 48.7 per cent of the 2011 TGD L homes analysed. The main loser is gas boilers at 4.6 per cent (-35.9 per cent), with oil at 0.3 per cent (-1.7 per cent), CHP at 0 per cent (-7.4 per cent) and direct electric at 0.1 per cent (-1.2 per cent). Another major shift is evident in ventilation systems, though 8 per cent of the dataset in this area and on airtightness tests is missing due to temporary issues with the National BER Research Tool which SEAI plans to resolve. Whole house extract ventilation systems – the category in DEAP which applies to mechanical extract ventilation with or without demand control – indicatively has 55.4 per cent of the market (+25.7 per cent), natural ventilation has 17.5 per cent (-27.8 per cent) and heat recovery ventilation has 17.4 per cent (-5.2 per cent). Compliance issues Alarmingly, 25.5 per cent of naturally ventilated homes built to 2019 TGD L have a

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q50 result of less than 3 m3/hr/m2 at 50 Pa. In apparent recognition that natural ventilation is not fit for purpose for airtight homes, TGD F 2019 (ventilation) does not include guidance for natural ventilation below a q50 score of 3. Overall, 85.7 per cent of homes built to 2019 TGD L which failed to comply with the requirement to conduct an airtightness test were naturally ventilated – suggesting that developers who persist in the use of natural ventilation may be more likely to fail to comply with other aspects of building regulations. The naturally ventilated homes also had the highest primary energy score – an average of 46.3 kWh/m2/yr, compared to 40.7 and 35.9 kWh/m2/yr for homes with whole house extract ventilation and heat recovery ventilation systems respectively. Average U-values for roof and floor are unchanged from the average for 2011 TGD L homes at 0.12 W/m2K, with walls improving from 0.18 for 2011 TGD L to 0.17 for 2019 TGD L. Meanwhile average window U-values improved from 1.21 to 1.17, and doors made a bigger leap, from 1.33 to 1.22. In terms of thermal bridging, 69.3 per cent of new homes used a Y-value of 0.08, compared to 68.8 per cent of 2011 TGD L homes, while 24.1 per cent (+2.5 per cent) used a value of 0.15, and 6.4 per cent (-3 per cent) used a figure of less than 0.08. The average airtightness test result of homes built to the 2019 regs is a q50 of 2.55 m3/hr/ m2 at 50 Pa, compared to an average for the 2011 TGD L homes of 2.81 – excluding homes which were not tested, where a default value of 7.0 was used. Over 5 per cent of TGD L 2019 homes failed to comply with the airtightness requirements, including 4.1 per cent where no airtightness test was done, and 1.3 per cent which had a q50 of more than the new backstop of 5. The data also shows the effect that the Covid-19 pandemic has had on housing completions. BERs were published for 6,267 new homes in the first 11 months of this year, where the year of construction was stated as 2020, compared to 9,842 for the same period last year. It’s unclear whether a surge in BERs in November are signs of completions

recovering to previous levels. In total, 11,096 BERs were published in 2019 for homes built that year, but the standing total has since grown to 16,986 homes, due to the lag of BERs published after the year of construction. The true total number of builds for 2019 is likely between 20-21,000 new homes, with the lower number of BERs due to non-compliance among self-builders with the legal requirement to obtain BERs prior to occupying the home. The SEAI data for 2019 includes 1,367 detached homes where the BER was obtained for occupation by homeowner, which indicates that this cohort are self-builders. Data on commencement notices from the Building Control Management System suggests that the true total number of self builds may be circa 4,000 new homes per annum. •

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Campaign launched to tackle whole-life environmental impact of buildings O n the five-year anniversary of the adoption of the Paris Agreement, the Irish Green Building Council (IGBC) launched a campaign to decarbonise Ireland’s built environment across its whole life cycle. The campaign is backed by Passive House Plus. As part of #BuildingLife, the IGBC will bring together representatives from across the sector to produce a science-based and industrybacked national decarbonisation roadmap for the built environment. IGBC CEO Pat Barry explained: “Most of industry and policy focus to date has been on tackling operational carbon – the emissions associated with the energy we use to heat and light our homes. But with half a million homes to be built by 2040, we cannot afford to focus exclusively on this. The conversation needs to move on to the total environmental impacts of the built environment across its entire lifecycle”. The #BuildingLife campaign aims to achieve the mix of private sector action and public policy necessary to tackle the whole-life impact of buildings. In Ireland, the project launched with the support of several high profile ambassadors including Dublin City Council’s city architect Ali Grehan, David Browne of RKD Architects, Lioncor CEO John Maxwell, Hines Europe’s managing director of technical operations Steve Murphy, Ecocem Ireland managing director Susan McGarry, and Passive House Plus editor Jeff Colley. Dublin city architect Ali Grehan said: “We cannot meet the goal of the Paris Agreement to limit global warming to 1.5 C by 2050, unless we tackle the environmental impacts of buildings across their entire lifecycle. I firmly believe that the public sector must lead by example, and I am thrilled to support #BuildingLife”. John Maxwell of residential property developer Lioncor also welcomed the campaign, stating: “I was delighted and honoured to be asked to be an ambassador for the #BuildingLife programme. Never before has the impact of our collective actions been so important in tackling climate change and together with the Irish Green Building Council, I hope to play my part in creating a roadmap for carbon life cycle regulation”. The IGBC will work on the #BuildingLife campaign alongside nine other European green building councils (GBCs). Each GBC will develop a national roadmap and together, they will work to develop an EU policy roadmap for building sector decarbonisation. At European level, the project launched with the support of three prominent members of the European Parliament: Ciarán Cuffe (Greens), Maria Spyraki (EPP) and Sirpa Pietikäinen (EPP). Irish MEP Ciarán Cuffe said: "I am delighted

to support the #BuildingLife campaign. A sustainable future in line with the EU Green Deal demands more action at EU level to tackle total carbon and resource impacts." The #BuildingLife campaign is supported by a coalition of funders focused on driving a more sustainable built environment. Today the Irish Green Building Council and its partners announced that two new grants — from the IKEA Foundation and Laudes Foundation, totalling over €3 million — have been secured. Currently EU and member state buildings policy only addresses energy use while buildings are operational. The #BuildingLife campaign focuses not only on the operational emissions of buildings, but also on the environmental impact of the manufacturing, transportation, construction, and end-of-life phases of built assets – often called embodied emissions – which account for around 11 per cent of all global greenhouse gases. Tackling these emissions is essential to addressing the total impact of the building sector and progressing towards the European Green Deal’s aim of a climate neutral Europe by 2050. Laudes Foundation head of built environment James Drinkwater added: “Accelerating industry, regulators and investors towards a net-zero carbon built environment is critical — and we must tackle emissions across the whole building life cycle if we’re serious about it.” The #BuildingLife campaign will aim to accelerate the ambitions of the European Green Deal in the building sector, and create the first region-wide response to the vision of a net-zero embodied carbon built environment as set out in the World Green Building Council’s 2019 report. The project will aim to create a pathway for other world regions to follow.

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The #BuildingLife campaign will do this by: •C reating a roadmap demonstrating how EU buildings policy can adopt whole life carbon targets •L aunching a new whole life carbon commitment within World Green Building Council’s global Advancing Net Zero project •E stablishing leadership groups on a European and national scale to contribute to the creation of national whole life carbon roadmaps towards net zero •S upporting the development of a building product database on the full environmental impact of different building materials •K ickstarting a communications campaign recruiting MEPs, policymakers and industry leaders to publicly advocate for a whole life cycle approach. •

Contact us for more information on how your brand can feature in our next issue. To enquire about advertising, contact Jeff Colley on +353 (0)1 2107513 or email *source, Passive House Plus Irish edition 2019 reader survey

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Grenfell inquiry hears of damning test culture B

efore it was halted until January 2021, the Grenfell Tower inquiry heard a series of damning testimonies on the culture towards fire safety within leading building material manufacturers and certification bodies in the years leading up to the fire. Insulation manufacturer Kingspan admitted to “shortcomings” in its testing and marketing material after the company withdrew three test results it had previously used to support claims that its phenolic insulation product, Kooltherm K15, was suitable on buildings over 18 metres tall. “We have now concluded that three tests carried out in 2005 and 2014 featured product that was not sufficiently representative of the product currently sold into the market place,” a company spokesperson told The Irish Times. Kooltherm K15 was used on approximately 5 per cent of the externally-clad area of Grenfell Tower after the project ran out of the main insulation product used, Celotex RS5000, a polyisocyanurate (PIR) insulation. In 2005, Kooltherm K15 passed a BS 8414 fire test — which mimics a fire breaking out of a window and coming in contact with external cladding — in a build-up using a non-combustible cement fibre cladding and cavity barrier construction. Counsel for Grenfell survivors Stephanie Barwise said this combination, “was not commercially available”. A different formulation of K15 was introduced a year later, and the successful 2005 test only applied to specifications where the same assembly was used, but Kingspan did not clarify this in its marketing literature, and continued to use the 2005 test to promote Kooltherm as suitable for high-rise buildings. Two further tests carried out in 2014 were also withdrawn by Kingspan as they were on test versions of K15 not sufficiently representative of the product on the market. Meanwhile, in one other BS 8414 test carried out by the company, including one on the new version of K15 in 2007, the assembly became a “raging inferno”, according to former Kingspan technical expert Ivor Meredith. “We were struggling to get the technology to pass, to justify our lie,” he told the inquiry. Meredith said he was shocked the insulation burned so ferociously, but that when he raised his concerns with managers, he was criticised for being too negative about Kingspan products. Meredith had a drug addiction and was

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later dismissed by the company. The inquiry also heard that Phillip Heath, a technical manager at Kingspan, had written in an email that facade consultant Wintech could “go fuck themselves” after raising concerns about the fire safety of K15 in one specification. Kingspan said that it was unaware its product had been used at Grenfell Tower until after the fire, and that it would have advised against its use with the aluminium composite material (ACM) that clad the building. Kingspan also said that it does not believe a different insulation specification would have prevented the spread of the fire, and that this view is backed by large-scale testing and peer-reviewed modelling. The company also says: “The company has now carried out extensive testing and re-testing which validates, for current K15, the BS 8414 performance claims made previously.” The Grenfell Inquiry is still trying to establish the exact contribution of different materials to the spread of the fire. In his earlier phase one report inquiry chair Sir Martin Moore-Bick concluded that “the principal reason why the flames spread so rapidly up the building was the presence of the ACM panels with polyethylene cores,” but also said the insulation materials behind the cladding “more likely than not” also contributed to the spread of the fire. The main insulation product used on Grenfell was Celotex RS5000. It was previously reported that Celotex used additional fire-resisting boards in a 2014 fire test of the product, though these were not declared in its subsequent marketing of the product. In November, former Celotex product manager Jonathan Roper told the inquiry this was done with the full approval of senior management and that the company’s actions had been “deliberately misleading and dishonest”. Roper said he had been asked to “lie for commercial gain”. “I went along with a lot of actions at Celotex that looking back on reflection were completely unethical,” Roper said. RS5000 initially failed its 2014 test, when flames reached the top of the nine-metre mock-up wall within 26 minutes. But a fire-resistant magnesium-oxide board was later added to the BRE test rig. The build up then passed the test, and Roper said that after he gave a presentation to senior management about the testing process, he was told to remove all reference to the failed test and the addition of magnesium

oxide boards. When the test report from the BRE was published it contained no reference to the fire-resistant boards. Celotex said in a statement: “These matters involved unacceptable conduct on the part of a number of former employees. They should not have happened and Celotex has taken concerted steps to ensure that no such issues reoccur, including the recruitment of new management to oversee its technical, operational and marketing teams as well as designing and implementing changes to testing processes and quality assurance systems.” The company also said that tests undertaken since the fire had verified the fire safety of RS5000. “In April 2018, a test of a particular rainscreen cladding system to BS8414:2 2005 in which RS5000 was one component was shown to meet the criteria of BR135 [fire performance of external thermal insulation for walls of multistorey buildings] which was the test result stated as having been achieved in Celotex’s products literature at the time of the Grenfell Tower refurbishment.” Meanwhile at the enquiry Sam Stein — a lawyer for the survivors and bereaved of Grenfell Tower — slammed the culture of testing and certification. “The public should have been protected from these ruthless and criminal manufacturers by the bodies who were responsible for testing and certification. But [they] provided no such protection. Instead they reinforced the dangerous and dishonest culture within the industry,” he said. “‘The BRE, the BBA, and others signally failed to discharge these responsibilities adequately. They were far too close to their customers. Testing was inadequate and certification haphazard.” At the inquiry it was also revealed that Claude Wehrle, head of technical sales at cladding manufacturer Arconic, had sent an email saying that a shortfall in the material’s fire performance was “something that we have to keep as VERY CONFIDENTIAL!!!!”. In a previous email Wehrle had said that Arconic was “very lucky” that a fire in Strasbourg had not passed to a nearby building that was clad with the product, Reynobond PE, and that “we really need to stop proposing PE [polyethylene] in architecture!”. The inquiry will resume in January after being halted before Christmas when a member of staff tested positive for Covid-19. •

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Northern Ireland claims 2012 regs meet NZEB NI still plans to tighten energy rules for new build

New research gives boost to recycled concrete


he Northern Irish government is preparing to update its building regulations to implement the nearly zero energy building (NZEB) standard, while simultaneously claiming that its current regulations meet the NZEB standard. Meanwhile initial analysis from Passive House Plus has indicated that homes built to Northern Ireland’s minimum standards may have close to double the energy use of homes built south of the border. In early December Northern Ireland’s Department of Finance published an information note on Part F of the region’s building regulations, which deals with energy performance, to clarify requirements regarding the NZEB standard. The note explained that Regulation 43B of the Building Regulations (Northern Ireland) 2012 requires that where a building is newly erected, it must be an NZEB. “This regulation implements Article 9 (1) of Directive 2010/31/EU on the Energy Performance of Buildings,” the note states, appearing to indicate that the region intends to continue to apply EU policy in this area in spite of Brexit. The information note goes on to state that meeting the target emission rate (TER) specified under Regulation 40 demonstrates compliance with the NZEB standard. This currently equates to a 25 per cent reduction in carbon emissions compared to 2006 standards. The minimum requirements – both in terms of the overall target and most of the elemental backstop requirements – are weaker than each of the last three revisions to minimum standards for dwellings south of the border, which respectively introduced 40, 60 and 70 per cent energy reductions compared to 2005 standards. A Northern Ireland Department of Finance spokesperson told Passive House Plus: “The Department is working to bring forward an uplift to the regulations as quickly as possible and has issued this Information Note while this work is ongoing. The Department is satisfied with the advice in the Information Note which clarifies that meeting the current requirements of Regulation 40 is the minimum standard of compliance with regulation 43B.” Passive House Plus asked the department what a typical minimum compliant new home would translate to in terms of calculated net primary energy use. “The net primary energy use and carbon dioxide emissions for buildings will vary depending on the size, shape and type of building and on the fuels used,” said the spokesperson. SAP calculations by Paul McAlister Architects seen by Passive House Plus showed a typical 94 square metre semi-detached house designed to marginally beat the Northern Ireland NZEB standard having a primary energy score of 82.5 kWh/m2/yr. By contrast, analysis by Passive House Plus of data from SEAI’s National BER Research Tool shows that comparably sized semi-ds south of the border designed to the NZEB requirements are averaging scores of circa 44 kWh/m2/yr in Ireland’s DEAP methodology, which was originally derived from SAP. •

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esults of a new five-year study of recycled concrete show that it performs as well, and in several cases even better, than conventional concrete. Researchers at the University of British Columbia’s school of engineering in Okanagan conducted side-by-side comparisons of recycled and conventional concrete within two common applications: a building foundation and a municipal sidewalk. They found that the recycled concrete had comparable strength and durability after five years of being in service. “We live in a world where we are constantly in search of sustainable solutions that remove waste from our landfills,” said Shahria Alam, co-director of UBC’s green construction research and training centre, and the lead investigator of the study. Waste materials from construction and demolition contribute up to 40 per cent of the world’s waste, Alam said. The researchers tested the compressive strength and durability of recycled concrete compared with conventional concrete. Concrete is typically composed of fine or coarse aggregate that is bonded together with an adhesive such as portland cement (which can also be partially substituted for low carbon products like ground granulated blast furnace slag). The recycled concrete replaces the natural aggregate for producing new concrete. “The composition of the recycled concrete gives that product additional flexibility and adaptability,” Alam said. “Typically, recycled concrete can be used in retaining walls, roads and sidewalks, but we are seeing a shift towards its increased use in structures.” Within the findings, the researchers discovered that the long-term performance of recycled concrete adequately compared to its conventional form, and experienced no issues over the five years of the study. In fact, the recycled concrete had a higher rate of compressive strength after 28 days of curing while maintaining a greater or equal strength during the period of the research. The researchers suggest the recycled concrete can be a 100 per cent substitute for non-structural applications. “As innovations continue in the composition of recycled concrete, we can envision a time in the future where recycled concrete can be a substitute within more structural applications as well.” The research was published in the journal Construction and Building Materials.


Bringing buildings into the circular economy Embodied carbon is the next great challenge for the building sector. For the group’s latest update, Marion Jammet of the Irish Green Building Council discusses initiatives underway at both Irish and European level to further cut the carbon footprint of the built environment.


espite the Covid-19 pandemic, 2020 has been a year of hope for anyone working for a more sustainable built environment. The programme of government and European policies have set ambitious retrofitting and climate targets. Funding for retrofitting almost doubled in budget 2021 and should steadily increase over the next few years. At EU level, the Circular Economy Action Plan and the Renovation Wave initiative both highlight the need to move towards resource and energy efficiency across buildings’ whole life cycle. Now that the vision has been set, concrete actions are needed to break down long-standing barriers to a more sustainable built environment. Addressing the total carbon impact of our sector New homes built in Ireland to new Part L regulations should be very energy efficient but focusing on operational emissions alone means we are only addressing part of our sector’s impact. Emissions are also released during the manufacturing, transportation, construction, and end-of-life phases of all built assets – buildings and infrastructure. These emissions, often referred to as ‘embodied carbon’, contribute to around 11 per cent of all global carbon emissions. Half a million homes will be built in Ireland up to 2040 – including 355,000 by 2030. This will have a significant impact on Ireland’s carbon emissions and the achievability of reaching carbon neutrality by 2050. In fact, the construction process alone — before these homes are occupied — will add more than 1.5 million tonnes of carbon emissions to the atmosphere each year. At EU level, a 2050 roadmap for reducing whole lifecycle carbon emissions in buildings will be developed by 2023. The EU’s Circular Economy Action Plan highlights that the strategy for a sustainable built environment to be published next year should be designed to ensure coherence across relevant policy areas — carbon, energy, resource efficiency and management of construction and demolition waste. It is also highly likely that resource efficiency and embodied carbon will be considered in the revised Energy Performance of Buildings Directive (EPBD)

to be published in 2021. In Ireland, international investors already set broader environmental requirements for the assets they purchase and operate. The Irish Green Building Council (IGBC) has developed the Home Performance Index certification to ensure broader sustainability issues, such as whole life carbon, are fully taken into account when building new residential developments. A growing number of product manufacturers have produced environmental product declarations (EPDs) over the last few months. EPDs are a standardised way for manufacturers to display information on the environmental impact of building products, including global warming potential. Ultimately, EPDs allow architects and other building product specifiers to make more informed choices about the materials they use. To support this transition, the IGBC has launched a new EPD campaign. As part of this campaign, leading specifiers such as ARUP, BDP, Coady Architects, Dublin City Council, Hammerson, Hines, IPUT, KRA, KSN, Meehan Green, RKD, Scott Tallon Walker Architects, Sisk, Transport Infrastructure Ireland and Wain Morehead Architects have committed to ask for EPDs and to prefer products with EPDs where possible (within procurement rules). Moving to a whole life carbon approach In September 2020, the IGBC — with support from the EPA and the EU-funded Life Level(s) project — organised a workshop to develop a set of recommendations on how to address whole life carbon in the built environment in Ireland. Measuring and reducing whole life carbon of buildings will tackle emissions from the building, transport and industrial sectors, but it will also radically reduce related waste and help transition to a circular economy. The 50 industry leaders who took part in the workshop first and foremost called for government’s leadership. Whole life carbon assessment is already a requirement at planning stage for all homes in the Netherlands and other countries are following, France in 2020 and Finland in 2025. The European Commission has launched the Level(s) framework for sustainable

buildings to standardise how this can be integrated into regulations and procurement. Yet, to date the huge upfront CO₂ impacts of new buildings are not measured or regulated in Ireland and the benefits of retaining existing buildings are not assessed. The government must send a clear message to the industry that a whole life approach to carbon neutrality is an absolute priority for new and existing buildings. The public sector must lead by example. In particular, public authorities’ purchasing power should be used to drive the demand for whole life carbon assessment and truly sustainable buildings. Initiatives such as Enterprise Ireland’s Green Start and Green Plus grants, which are there to help Irish manufacturers developing EPDs, are key to support this transition. But other actions are needed. These include awareness raising campaigns, training and the development of highly practical, high-quality case studies. A full section of the IGBC’s online learning hub now focuses on resources and circularity. This includes webinars on life cycle assessment, embodied carbon, EPDs, circular construction and minimising waste on site. In early 2021, the IGBC will run life cycle assessment training courses for building professionals. A half-day circular construction conference will also be organised in June. •

For further information on the Irish Green Building Council and to access the resources of the learning hub, visit To join the EPD campaign, visit

ph+ | igbc ph+ update | news | 21



A precursor to the passive house In his latest column on the development of passive and solar buildings in the 20th century, Dr Marc O’Riain looks at what might be considered an early prototype in the development of passive houses: the 1974 Philips Experimental House.


e all have an innate understanding of the principle of passive first, but where did this come from? Almost 50 years ago a project by Philips in 1974 in Germany set the basis for passive house solutions in 2020. Philips built a computer controlled, super-insulated experimental house to explore the potential of low temperature output heat pumps to deliver space heating. The researchers, Bruno, Hörster and Steinmüller soon discovered that their passive actions were more cost optimal than the active solutions. They needed to reduce the potential heat demand of the ‘Experimental House‘ to make the heat pump viable. They super-insulated the 147 m2 study building with elemental fabric standards of 0.17 W/m2K for walls, roof, and floor. This was compared to German and Swedish standard constructions where 1.12 W/m2K and 0.37 W/m2K were the fabric standards for walls respectively. The Experimental House had a startlingly low heat demand, comparable to A-rated houses today, and all in the absence of triple glazing, airtightness and thermal bridging knowledge. The passive measures reduced the heat demand to less than 13 per cent of a normal German house or 800 kWh per year (see figure 1). They then met this remaining demand with renewable systems such a 90 per cent efficient heat recovery ventilation system, a heat pump soil heat exchanger in the basement and an experimental solar vacuum collector on the roof. Whilst the researchers would not realise that the computer might not accurately project the counter-effective impact of human occupant behaviour, they did manage to model internal heat loads and the effect of opening windows. A series of other research findings since, have found that occupants of low energy houses are more carefree about heating, more likely to turn the thermostat up, leave the windows open or forget to close the shutters at night. Some researchers have even found that dwellings designed and equipped to be low energy can in fact be comparatively less efficient than higher energy consumption buildings because of human behaviour (Dugar 2019i). The Experimental House researchers did find that in almost all of the cases the contribution of ambient air infiltration, which can result from opening windows, had a “negligible” impact on heat demand. One 22 | | issue 36

of the findings that fascinated me was their measurement of heat gains from passive solar gain, plus building occupants and equipment: “20,000 kWh yearly energy gains (10,800 kWh from solar radiation, 9,250 kWh internal load)”. These gains plus the output of the heat pumps are enough to meet space heating demand in the Experimental House. Something I managed to grasp easily is the reported average heating demands which were 6 kW, 1.9 kW and 0.5 kW for the German, Swedish and Experimental Houses respectively. If you’re used to going out and buying a stove or heat pump this should give you a good sense of the scale and size of heating system required in these 1974 houses. That’s kind of mind blowing when you think it’s nearly 50 years ago.

that in most climates, measures that focus on the ‘passive’ side of the building - especially the largely “passive” building envelope and its heat losses or gains - tackle the problem at its root and are much more effective than measures on the ‘active’ side.” Many thanks to CIT librarian Noreen O’Neill for finding Dr Steinmüller’s original article. In my next article we will be looking back to the States and the Lo-Cal House in the mid 1970s. n

The Experimental House had a startlingly low heat demand The team also conducted fascinating research on the heat demand reduction of a number of options on a normal German house, with insulated shutters on external windows resulting in a 16 per cent reduction and double glazed windows over single glazed resulting in a 13 per cent reduction. They also found that increasing window sizes on the south facade would not result in enough solar heat gain to offset the heat lost through the windows, even when windows with insulated shutters and an overall (night time) U-value of 0.6 W/m2K are modelled, when compared to the 0.17 W/m2K walls. Maybe there is a lesson for us all there. The overall findings, far from being a disaster for Philips, showed that the reduced heat demand made the low-level thermal capacity of their heat pump a feasible alternative to oil, gas or solid fuel. This article heavily depended on the firsthand research of Dr Bernard Steinmüller and his excellent 1979 article ‘The Energy Requirements of Buildings’ii. Reflecting on that paper, Steinmüller told the 2019 International Passive House Conference: “It turned out

(above) Space heat demand in the Experimental House and comparison dwellings. Dugar, Yash (2019), ‘Investigating the effect of human behaviour on the energy performance of 3 typical Dutch residential dwellings using sensors and dynamic performance modelling’, TU Delft Civil Engineering & Geosciences



teinmüller, B. & Bruno, R. (1979): The Energy Requirements S of Buildings, Energy and Buildings, 2, p. 225 – 235.

Dr Marc Ó Riain is a lecturer at the Department of Architecture at Cork Institute of Technology, one of the founding editors of Iterations design research journal and practice review, a former president of the Institute of Designers in Ireland, and has completed a PhD in low energy building retrofit, realising Ireland’s first commercial NZEB retrofit in 2013.

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On the need for (moisture) balance Dr Peter Rickaby writes on the varied and complex challenges of retrofitting older buildings.


orking on technical risks in retrofit has convinced me that most of those risks are related to moisture in some way, so it is perhaps not surprising that I find myself at the UK Centre for Moisture in Buildings (UKCMB), where our objective is to understand and promote moisture safe construction and retrofit. When he founded UKCMB, Neil May emphasised that we don’t yet know enough about how moisture behaves in buildings. That is a research challenge that many colleagues at UKCMB and elsewhere are addressing, but Neil taught us that in the meantime, while we investigate, the watchword is caution. Moisture safe retrofit is cautious retrofit, and caution is one of the ‘four Cs’ promoted by Neil May’s BSI paper (written with Chris Sanders) ‘Moisture in Buildings: an integrated approach to risk assessment and guidance’, and by the forthcoming new edition of British Standard 5250 on the control of condensation in buildings. Caution is important where a traditionally constructed or protected building is concerned, where the moisture balance of the building often depends on vapour-balanced construction embodying vapour permeable materials. Throughout my work on the Each Home Counts review, and on the UK’s new publicly available specifications (PASs) for retrofit, there has been a strident background

some form of infill, and they often featured porous brickwork, lime mortar, lime plaster and lime render. Many of those that have been protected by listing or conservation areas are little changed since they were built, and their construction often remains vapour balanced despite changes in the way we use them. These are buildings that require cautious, special treatment. However, when we examine other pre-1919 buildings we find that over the century since they were built many of them have been extensively modified: they have been re-pointed with cement mortar, some walls may have been rendered with cement render, many walls will have been replastered internally with gypsum plaster, and most rooms will have a couple of coats of acrylic paint. There will also have been modern extensions, added insulation, new heating systems and perhaps even added ventilation. To what extent do these buildings still retain vapour permeable construction, and in what sense do we still use them in the way intended when they were originally built? They have been adapted to twenty-first century life, and they have assimilated new materials and technologies. The other area of concern is how we talk about vapour permeability. There is a strong tendency to treat materials and products in

In many older buildings every element may have its own moisture balance. chorus of voices from groups interested in traditional buildings, encouraging us to give those buildings special treatment because of their vulnerable, vapour-balanced construction. They are correct, of course, but sometimes I think the messages have been exaggerated. There are two areas in which I think a more nuanced approach might be more appropriate and helpful. My first area of concern is the number of buildings that are claimed to need special treatment. Traditionally constructed buildings, usually defined as those built before 1919, are estimated to account for between a fifth and a third of the UK building stock. They originally had solid masonry (brick or stone) walls or timber-framed construction with

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a binary way – they are either vapour permeable (or ‘vapour open’ = good) or they are not (‘vapour closed’ = bad). This black and white distinction is nonsense. Vapour permeability is an attribute that has a value on a scale from almost vapour open to vapour closed (e.g. from tissue paper to polythene), so every material is a different shade of grey. When we look at traditionally constructed buildings, this is what we find: lots of materials and constructions that are to some degree vapour permeable. How can we turn these observations into actions that help us deliver moisture-safe retrofit? Most buildings are moisture balanced, of course, irrespective of their age or type of construction, unless they are showing symptoms of imbalance such as condensa-

tion and mould, rising damp or water penetration. Where a building is imbalanced, we might rebalance it by moving it in either direction – towards vapour closed construction or towards more vapour permeable construction, or we might just ventilate it better. We might seek to restore the original balance or to establish a new balance appropriate to a new use or new circumstances. This approach applies not just to the whole building, but also to its various elements, particularly external walls but also exposed floors and to some extent roofs. In many older buildings every element may have its own level of vapour permeability and its own moisture balance (or not), and a sensitive, perceptive retrofitter will recognise those attributes and seek to preserve or adjust them accordingly. Recently I was struck by my Retrofit Academy colleague Lisa Pasquale’s detailed retrofit interaction with every tiny element of her own Glasgow tenement flat – always seeking enhancements that will improve energy performance while maintaining or improving moisture balance. Lisa cites the work of Harry Paticas, of Arboreal Architecture in London, whose projects also involve detailed, cautious interactions with even small parts of single elements of buildings. I once referred to Harry Paticas’s work as “precious”, but I have learned that we need that very detailed and cautious interaction with older buildings, if we are to maintain and promote moisture balance as we work through our building stock, improving its performance while preserving our architectural heritage. n

Dr Peter Rickaby helps to run the UK Centre for Moisture in Buildings (UKCMB) and the Building Envelope Research Network at University College London. He also chairs the BSI Retrofit Standards Task Group and was technical author of the new domestic retrofit standard ‘PAS 2035: Retrofitting dwellings for improved energy efficiency — specification and guidance’. He is currently working on ‘PAS 2038: Retrofitting non-domestic buildings for improved energy efficiency — specification’. The views expressed here are his own and not necessarily those of UKCMB, UCL or BSI.

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Building: 164 m2 detached passive house Build method: Cavity wall Site & Location: Suburban site, Bandon, Co Cork Standard: Passive House Classic certified

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A stunning new passive house in Cork breaks the conventions of passive house form with a design that manages to be both dramatic yet discreet at the same time, inspired by a US project to contort itself beautifully into its steeply sloping site. Words by John Cradden




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The Bandon passive house (top) was inspired by the Guilford Sound Artists’ Residence (above), by Ryall Sheridan Architects.


his modestly sized single-storey home in the West Cork town of Bandon is an uncompromising design intended to blend seamlessly into its surrounding landscape and be discreet from the road. But it also surprises you with spectacular architectural drama as soon as you walk through the entrance. Inspired by an artist’s retreat in Vermont, USA that was designed by New York passive house architect William Ryall, this passive-certified four-bed dwelling looks like it should be located somewhere deeply rural but is actually well within the confines of the Bandon suburb of Old Chapel. The large field on which it sits is part of a family landholding well within the development boundary of the town, which made planning permission a quick and straightforward affair. But what set off architect Paul McNally’s imagination was the geometry of the site, namely the presence of a steep slope running from north to south across the site down to a small stream that eventually guides your eye to a ruined mill on the horizon. In

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order to take advantage of the dramatic landscape, he picked a spot on the site that allowed the mill to be aligned within a crest in the valley. A couple of years before he met the clients, McNally had spent some time with Ryall during a conference organised by the North American Passive House Network in New York. McNally had seen Ryall presenting his Vermont artists residence project the previous year. “That project really kind of stuck in my mind when this one came up for design,” he said. Although it’s a much larger building, it’s easy to see the influences on this site-specific Bandon project, such as the way the entrance cuts down into its steeply sloping landscape, but also the idea of mounting the earth onto a retaining wall at the entrance to this building, which is topped by a green roof. “So, it creates a very dramatic approach to our building where you’re walking down the slope,” said McNally. That detail aside, approaching the building from the road doesn’t give you any hint of what’s behind the entrance, but this is ex-

actly what the clients wanted. To the left of the front door is a somewhat austere blank, larchclad wall which helps fulfil the brief to keep it discreet and private from the road. Indeed, the only bit of engagement is the entrance area, and this aligns with McNally’s preference for making the entrances to buildings as clear as possible. “I think that’s it’s a nice thing to do architecturally, to kind of lead people very directly in the building. And then the opposite happens once you enter the building; the building is very open.” It takes a drone video of the house (which you can see on to get any hint from the outside at what’s across the threshold. From above, you get a much better sense of the shape and drama of this very geometrical, zinc-roofed building, with its mixture of acute and obtuse angles, and an orientation that cleverly tracks the sun. As you walk in, there’s the ‘singly loaded’ corridor to the left, which is on the other side of the blank entrance wall. The corridor runs north to south with roof lights over it and is bookended by a large window, with bed-



rooms all facing east to capture the morning sunshine. Once inside you’re also quickly enveloped by the open plan area, with floorto-ceiling glazing on three different facades each facing in various angles to the south and southeast, as well as massive roof lights above. In what may well become a defining feature of low-energy homes over the next few years, and is already a regular feature of McNally’s more recent designs, the three south-facing facades have extensive set-back glazing to provide vital shading, a way of integrating shading into the form of the building as opposed to tacking on awnings, overhangs or trellises. “This way is not the cheapest way of doing it, but it’s doing more things than just throwing some shade on it, it’s creating a visual rhythm across the facade of the building as well,” said McNally. “As well as creating a horizontal shade, it’s creating lateral shading because the sidewalls come out.” It’s certainly an example of great design that also delivers for energy efficiency and occupant comfort, while also breaking the convention that passive house form should be relatively simple and cubic. “What I’m trying to do is create a building that is beautiful architecture and to show architects that if you start off with the skills of knowing how to detail things, how to deal with thermal bridges, how to deal with shading, how to design buildings appropriately — that if you absorb them into your toolbox of skills you should then be able to move on and invent an architecture that is both beautiful and effective,” McNally said. What also surprises is that the relatively small size of the dwelling – 164 square metres – doesn’t limit its architectural impact, but it certainly enhances its green credentials. “We have to think about sufficiency as well. Just because a client could build a larger building doesn’t mean they should. It affects costs. If you build more of it, there are more carbon emissions as well. So, there are many reasons to not do a huge building.” There were a few challenges to get this masonry building airtight, arising mainly from two culprits: the floor and the higher-level opening windows. The problem with the windows was down to the automatic actuators that were installed to enable them to be opened at the touch of a button, because they’re hard to reach. The windows had passed a preliminary airtightness test before the actuators were put in. Actuators hold the window closed at a single point, as opposed to the three points typical of a single handle, which can mean the seal isn’t as effective. The problem was eventually resolved, but this episode suggests there might be a gap in the market for airtight actuators. There was also an issue with some structural sections that join the lower windows with the upper windows, and where it was

It creates a very dramatic approach to our building

Photos: Janice O’Connell / F22 Photography | Site photos: Paul McNally Guilford Artists’ Residence: Ryall Sheridan Architects

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A SMARTER KIND OF ROOF LIGHT The roof lights are an interesting feature in themselves. Custommade by Precision Quality Glass, they are designed to be much better than standard roof lights in terms of thermal detail, according to Paul McNally. “When we were doing the PHPP calculations, there would have been a penalty if we’d used standard roof lights.” The thermal weak point of most roof lights is the upstand on which it sits. McNally’s solution was to install a triple glazed unit down in line with roof, as opposed to sitting it on top of it. In a way, it’s a little bit like installing a window in the external insulation layer of a building rather than between the blockwork. Because the roof light is not sitting proud of the roof, there is just a single layer of glass up on top where the normal roof light would be to act as the rainscreen, so McNally has essentially separated the thermal function from the weathering function. “But it’s more tricky to build,” he said. A unique virtual technical walkthrough of this project is available to explore at tinyurl. com/BandonPH.

1 Toughened glass rain screen; 2 Triple glazed unit; 3 Coloured (white) glass liner; 4 Intello vapour control layer; 5 Mineral wool insulation between timber studs; 6 Elke Strongboard; 7 35 mm Gutex Multiplex Top with Heco fixings; 8 Solitex breather membrane; 9 44 mm treated timber batten with ventilation & softwood boarding with vent gaps, zinc roofing; 10 Rafters to fall; 11 Solitex breather membrane; 12 Mineral wool insulation between 125 mm cross timbers; 13 Mineral wool insulation between 250 mm cross timbers; 14 Intello vapour control layer above mineral wool insulation between 2 layers 44 mm timber batten with plasterboard; 15 Fritting

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The whole thing is set out to catch the sunlight all day

impractical to apply airtightness tape. This was resolved with a pro clima liquid airtight membrane. By far the more serious airtightness issue was the floor. It suffered a surprising amount of leakage, which McNally believes was because of the particular build-up they chose. As an alternative to laying a thick, 150 mm concrete slab on top of insulation, they chose to go with a sub-base concrete slab with rigid insulation and a screed above, because of the length of time a thick slab would take to dry out. However, there were air leaks where the internal partition walls met this floor build up, so again they painted a layer of pro clima liquid membrane at the junction here. Issues like the airtightness, along with the attention to detail required, as well as the fact of it “not being a run-of-the-mill build” made this project a massive learning curve for the contractor, Chris O’Donovan and his team. “The fact that it is a masonry build made it harder compared with timber frame, where you can wrap the whole house and make it line up as a total envelope. But with this, you have to go stage by stage, you have to get the plan right, you have to get all the blockwork sealed up and so it is an extra challenge to make it, to get it there.” McNally said that building in timber frame was an option, but this would have added about 5 per cent to the overall build cost, and there was a need to keep costs down where possible in order to deliver the overall goal of a passive house. O’Donovan is certainly taken by the final result. “The design is magnificent; the whole thing is set out to catch the sunlight all day. It’s also got a good contrast between glass all the way to a section where there’s a grass roof. And then you have a section that’s clad with larch, you’ve got these concrete walls through the middle as well, so it’s a good mixture and blends in very well together. I love the zinc roof, it really is massive, with a really good finish and designed very well.” The way the building is laid out to react to the sun is also what makes McNally smile. “So, the bedrooms all face east so every morning you’re going to be greeted by the morning sun. So that’s going to get your circadian rhythm kicking in. And then you come out, you move to have breakfast and the sun, by late morning, is now presenting around into your kitchen space and your island where you’re going to be sitting, having your breakfast. Then by midday and afternoon, it’s faded, and it’s coming into the dining area. By evening, it’s shining into the living room. I think that the daylight quality of this building is going to be incredible.” The clients have yet to move in at the time of writing, partly because of Covid-19, but it’s understood they’re itching to get in. “The client said at one point, just experiencing the building as it moved towards completion, that her favourite room so far was the corridor,” said McNally. “That’s a remarkable comment to make, to think that you’ve nailed the design of a corridor.”

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

ph+ | cork case study | 31

CASE STUDY Transparently exceptional


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1 Single course of Mannok Aircrete block around floor perimeter; 2 Farrat plate thermal breaks under stub columns.; 3 extruded polystyrene in the cavity at foundation; 4 strategically positioned Mannock Aircrete blocks ; 5 Ancon TeploTie low thermal conductivity wall ties; 6 Bosig structural insulation boards at window junctions; 7 pro clima liquid airtight membrane applied to inner wall & floor junction; 8 the steel and timber roof structure reflect the building’s unusual geometry; 9 the VMZinc roofing membrane and bespoke roof lights awaiting the installation of the external single glazed unit; 10 architect Paul McNally, who has carved out a niche as a pioneering passive house architect with an eye for design.


SELECTED PROJECT DETAILS Client: Private Architect:: The Passivhaus Architecture Company M&E engineer: DKP International Main contractor: Chris O’Donovan Construction Ltd Quantity surveyors: Byrne & Co. Mechanical contractor: Ciaran Keohane Airtightness tester/consultant: Clean Energy Ireland Cavity wall ties: Ancon wall ties from Leviat Structural insulation boards: Bosig, via Ecological Building Systems Woodfibre boards: Gutex, via Ecological Building Systems Vapour & airtightness products: pro clima Windows & doors: Munster Joinery Roof windows: Precision Quality Glass Entrance doors: Munster Joinery Flooring: Wood Flooring Ireland Roofing: Wychbro Coppersmiths Heat pump: Daikin Ireland MVHR: Dantherm, via BEAM/JFL Powervac Solar PV: Advanced Heating & Energy System

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At Chris O’Donovan Construction we offer a complete range of services, from A-rated passive house new builds and home retrofits, to energy efficient extentions and renovations.


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CALL NOW! +353 (0)21 439 5344 34 | | issue 36




IN DETAIL Building type: Detached 164 m2 cavity wall house

Airtightness: 0.635 ACH at 50 Pa

Location: Old Chapel, Bandon, Co Cork

Thermal bridging: First course of Quinn Lite blocks, low thermal conductivity cavity wall ties, thermally broken window frames, insulated reveals. Y-value (based on ACDs and numerical simulations): 0.026 W/mK for ambient thermal bridges, 0.040 for perimeter thermal bridges.

Completion date: October 2020 Budget: Not disclosed Passive house certification: Passive House Classic certified Space heating demand (PHPP): 9.9 kWh/m2/yr Heat load (PHPP): 12 W/m2 Primary energy demand (PHPP): 70 kWh/m2/yr Primary energy renewable: 39 kWh/m2/yr Heat loss form factor (PHPP): 4.45 from PHPP Overheating (state PHPP): 8% of time greater than 25 C Number of occupants: 2 BER: Not yet complete

Energy bills (measured or estimated): Using delivered energy figures from PHPP, and assuming 50 per cent of energy generated by the solar PV array is used on site, Bonkers. ie suggests a cheapest available tariff of €734 per year for all electricity (or €409 plus standing charges, VAT & PSO). Applying the contribution of PV proportionately to each type of energy use within the house, the estimated annual space heating & cooling bill is €176.16, inclusive of all charges, or €14.68 per month. Ground floor: 150 mm Xtratherm insulation with concrete slab (40 per cent GGBS). Mannok Aircrete (formerly Quinn Lite) block and extruded polystyrene in the cavity at foundation U-value: 0.142 W/m2K Walls: New build masonry. Render on blockwork followed inside by 250 mm full-fill graphite enhanced-bonded bead insulation to cavity with Ancon TeploTie wall ties, blockwork and plaster finish internally.

U-value: 0.126 W/m2K Roof: Ventilated zinc cold flat roof followed underneath by 45 mm Gutex Multitop, 18 mm Smartply, 340 mm Isover Spacesaver mineral wool, pro clima Intello membrane, 88 mm service cavity with mineral wool. U-value: 0.103 W/m2K Windows: Triple glazed Munster Joinery Passiv AluP aluminium window with insulated core. Overall U-value: 0.80 W/m2K Roof windows: Triple glazed units custom manufactured by Precision Quality Glass. Rainscreen at roof level. U-value: 0.8 W/m2K Heating system: Daikin Altherma air-to-water heat pump, 180 litre hot water tank with COP of 6.11 for space heating (35-degree flow rate) and 2.52 on domestic hot water Ventilation: Dantherm HCH5 mechanical ventilation with heat recovery. Passive House Institute certified to have heat recovery rate of 81 per cent. Electricity: 20 m2 JA Solar photovoltaic array with estimated annual output of 3,519 kWh (PHPP), or 21 kWh/m2/yr Green materials: Wood fibre roof insulation from Gutex, FSC-certified Siberian larch cladding, GGBS cement.

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Measured total of €1,500/yr total energy bills (See In detail panel for more information). Building: Deep retrofit to 179 m2 Victorian semi Build method: Retrofit with timber frame & cavity wall extension Site & location: Phibsborough, Dublin 7 Standard: Low energy retrofit

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THINKING INSIDE THE BOX VICTORIAN SEMI RETROFITTED AS A HOUSE WITHIN A HOUSE Facing the challenge of how to bring a Victorian home with damp old brick walls up to a modern low energy standard, architect Brendan O’Connor deployed an innovative solution: build entirely new and super-insulated timber frame walls within the old structure. Words by David W Smith

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He came up with the striking concept of building an entire timber-framed house within the brick structure.

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iamh Collins describes her retrofitted Victorian house in Dublin as having “a really healthy body with clothes from Primark”. Niamh bought the property in the suburb of Phibsborough, near the North Circular Road, for €520,000. But rising damp was rife and the house needed a lot of structural changes as it had been split into four bed-sits. To save money, the architect Brendan O’Connor came up with the striking concept of building an entire timber-framed house within the brick structure. Despite his innovative approach, the bill for renovation came in at around €400,000, leaving Niamh no spare money to decorate, or even buy a new front door. “My thinking was that a healthy body will last a long time and the clothes can always be upgraded. Things like decoration could wait until I had more money. I’ve always believed that if you have to do the right thing, even if it’s hard, then you still do it and I knew I’d never have a second chance to get it right,” said Niamh, a consultant in emergency medicine at Connolly Hospital, in Dublin. When looking for a new home, Niamh’s overriding goal was to live in a warm, low energy house. As a child in Dublin, she had grown up in a freezing seventies-built house and had never lived in a warm home. The other imperative was to live close to central Dublin. “I grew up in suburbia but I’m a city girl at heart,” she said. When she saw pictures of the house in

2014, it was love at first sight. She told the estate agent she was going to buy it. There were other potential buyers at the open viewing, but Niamh ensured she had an edge. “My aunt once wanted to buy a house she couldn’t afford, and granny told her to bury a miraculous medal. Sure enough, the owner liked her so much he sold it for less. I don’t believe in miraculous medals, but I do believe in my granny. So, I went to the viewing with a miraculous medal, dug a hole with my heel in the garden, and planted it,” she said. Niamh won the bid and put down a deposit in September 2014, but the sale proved complex and stressful, and she didn’t get hold of the keys until February 2017. “It took patience and wrangling. A friend said the house was ‘like a bad boyfriend’ that wouldn’t date me but wouldn’t dump me either. The day I got the keys I told her ‘bad boyfriend turned good’.” Her first intention had been to insulate thoroughly and install standard central heating and a gas fire. But a few weeks before the sale went through, she visited her cousin in a new home built to the passive house standard. “She was walking around barefoot in January with a new baby and telling me her energy bills were less than €1,000 a year,” she said. The visit was timely. Niamh decided to retrofit the house to higher environmental standards. She began searching the internet for information but could not find any suitable


guidance. “There’s an enormous need for a textbook, but there’s nothing available. What I wanted was to work out 70% of where I had to go, then consult the professionals for the extra bit,” she said. “A lot of the self-build magazines didn’t address the issue of breathability of the brick, and there was a lot of commercial advertising.” Niamh’s frantic googling eventually turned up the name of architect Joseph Little, now assistant head at the school of architecture at Technological University Dublin, and a leading expert on moisture in buildings. Little had previously been in practice with the architect Brendan O’Connor, who now runs Abode Design, and is himself a specialist in low energy retrofit of old buildings. By a roundabout route, Niamh had found the right man. When Niamh contacted Brendan, she already had clear ideas about what she wanted. She had taken design courses and had pages of notes in a copybook describing how she wanted to live her life. “It was a bit of a campaign for Niamh and she was very much part of the design team. I’ve worked for a few medical clients and they tend to be analytical, evidence-based. It’s a pleasure to work for them,” Brendan said. Discussions began about the design in February 2017 and continued into April. Niamh had four non-negotiables. The first three were high-quality wooden floors, an air-to-water heat pump and high-quality

Photos: Paul Tierney

internal, breathable insulation. The fourth element was more complicated. She insisted on installing a glass-to-glass corner unit in the kitchen to take advantage of the views across the south-west facing garden. “Brendan tried to talk me out of it as it involved cantilevered engineering. It would have saved thousands of euros. But I just said no!” In May, Niamh started searching for a builder and Brendan came up with a few recommendations. As soon as she spoke to Kevin Doyle, of Doyson Construction,


she liked his direct, open style and agreed a negotiated tender. In June and July, they finalised all the details. Niamh was meticulous in planning the build as she could not afford for costs to rise. The biggest problem was rising damp. The walls had been injected before with damp-proofing and Niamh did not want to repeat it in case the old bricks crumbled. Brendan proposed lime-based, breathable solutions, but they were prohibitively expensive. He was forced to think laterally

ph+ | dublin retrofit case study | 39




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and came up with the innovative idea of building the timber-framed structure inside the brick. “When you cut off the shell from the central heating, it’s a lot easier to get to the condensation, or unfavourable dew points, as the surface of the masonry remains cold and never has a chance to dry out,” he said. “We had to accept the brick would be damp and work around it. But the timber frame has a breathable membrane and an airtightness membrane. It’s important there’s a ventilation gap behind the frame that allows the bricks to be vented. “We also put a siloxane application [on the brick walls] that prevents water seeping into the brick work, but still allows water vapour to escape. The theory is that over time the brick work will dry out and improve the health of the building. We also added perforated drainage around the perimeter of the existing brick house that takes the water pressure away from the wall.” Brendan had never tried the strategy on an entire house before, but he once deployed it on the damp and bulging party wall of a low energy refit in Blackrock, Dublin previously

covered by Passive House Plus magazine. “The old stone party wall bulged so we put a new plumb well-insulated timber frame wall inside it, with a breather membrane on the outside and airtightness membrane on the inside. That time, it was more of a problemsolving exercise on one area, but it informed the work on Niamh’s home.” A more superficial approach to the retrofit could have saved money but had terrible long-term consequences, Brendan says. “The minute you start a low energy retrofit you have to think about the responsible way to deal with ventilation and airtightness. If you don’t do it in the right way, you’ll get condensation issues when the relative humidity increases due to the airtightness.” Building the frame inside the old walls meant shrinking the rooms. Installing breathable insulation would have lost 120 mm of space. The addition of the timber frame extended it to 200 mm. But the generously sized rooms with their high ceilings were not noticeably affected. Kevin Doyle’s work on the house began in August targeting a March finishing date. There were a lot of structural changes and he


I’ve worked for a few medical clients and they tend to be analytical, evidence-based.

ph+ | dublin retrofit case study | 41



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1 & 2 Front and rear of the existing Victorian house prior to renovation; 3 a lot of structural changes were needed, and the entire ground floor was excavated to accommodate new floor build-up; 4 architect Brendan O’Connor discussing the project on site prior to installation of the internal timber frame; 5 the walls of an earlier extension were knocked; 6 the side wall was then rebuilt to allow for the cantilever to support the glazed corner unit; 7 pro clima Intello membrane fitted internally to walls, with airtightness taping; 8 underfloor heating installed throughout the ground floor.

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removed everything except the stairs, three walls and the upstairs floorboards. His team put in the floor insulation, membranes and damp proof courses, retiled at the back of the house, and constructed the timber frame. They rebuilt the side back wall to allow for the cantilever to support the corner unit and constructed a cavity wall extension with full-fill insulation. The house has triple glazed windows and two wood-burning stoves. The build followed passive house principles, but Brendan says certification was never a realistic goal for the retrofit of a damp Victorian brick house with granite detailing. It performs “vastly better than normal Victorian houses”, however. The building energy rating (BER) before the build was a G and it jumped to an A3. Meanwhile, the airtightness test showed 4.69 air changes as opposed to more than 20 before the retrofit. The uplift would have been higher, but problems with the party wall have dragged it down. “It was hard to tackle the party wall with insulation as parts penetrated into the neighbouring property and we couldn’t make the stairs any narrower,” said Brendan. “The first test showed we were losing air

through the party wall and nowhere else. We decided to live with it as any air being transferred was from one heated space to another. It’s a big job to fix it but it could be done if necessary. But the heat pump has not struggled, and Niamh’s heat bills are not high, so it’s performing as a low energy house should.” Kevin would have finished the build in time on March 16, but Storm Emma struck at the start of the month. He drove up from Carlow to secure the house, but there were a few delays and it was completed at the end of March. Niamh moved in on April 25 with her newborn baby boy. She loves living in the house, which is on a quiet street, minutes on foot from central Dublin. Most importantly, for the first time ever, she’s not living in a fridge. The finished house features Aereco demand-controlled ventilation and a Daikin air-to-water heat pump. Downstairs the heat pump supplies underfloor heating while upstairs there are low-temperature radiators. Niamh’s bills so far for electricity and gas average €120 a month in a 200 m2 house. The figure will be even lower once she saves the money to replace the leaky front door.


“The only disadvantage of living in a warm house is the Christmas tree doesn’t last as long,” she says.

SELECTED PROJECT DETAILS Client: Niamh Collins Architect: Abode Design Main contractor: Doyson Construction Civil & structural engineer: Loscher Moran Design Practice Energy consultant: OTE Solutions Mechanical contractor (heating & DHW): Keltic Renewables Airtightness tester: Greenbuild Cavity wall & floor insulation: Xtratherm Additional wall insulation: Knauf Roof insulation: Isover Airtightness products: Ecological Building Systems Windows: Novus Windows Corner window & slider: Internorm, via J+N Passive Windows Roof windows: Tradecraft Heat pump: Daikin Wood burning stoves: Agathos Ventilation: Aereco Kitchen: Kitchen Space

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 &

ph+ | dublin retrofit case study | 45



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46 | | issue 36

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IN DETAIL Building: Existing Victorian house that had been broken up into four flats was returned to a single-family dwelling with single-storey rear extension, total floor area 179 m2. Location: Phibsborough, Dublin 7 Budget: €400,000 for the retrofit (approx), €520,000 for the original dwelling. Niamh also availed of some small grants, namely €3,050 from the SEAI Better Energy Homes scheme and €1,650 in carbon credits on her electricity bill. Completion date: March 2018 BER Before: G (522.49 kWh/m2/yr primary energy) After: A3 (73.68 kWh/m2/yr primary energy) Heating demand: According to DEAP, the projected space heating demand (delivered energy) for the primary and secondary heating systems combined is 3,634 kWh per year (2,192 kWh provided by the heat pump, and 1,442 kWh via the wood burning stoves), or 20 kWh/m2/yr. This comes to a calculated space heating cost of €369/yr (€289 for the heat pump, based on cheapest available tariff of 13.2c per kWh including VAT, and an estimated fuel cost of 5.57c per kWh of delivered energy for bulk delivered softwood, as per SEAI’s domestic fuel comparison of energy costs from October 2020.) Measured energy consumption: According to the electricity meter the house consumed 7,367 kWh for household electricity, space heating & hot water, or 41 kWh/m2/yr (note the house uses a gas cooker), between 15 September 2019 and 15 September 2020. This is very close to the delivered energy requirement estimated by DEAP of 39 kWh/m2/yr. Energy bills: Niamh Collins says her electricity bills average €50-65 from April

to September and from €150 to €250 per month from October to March. She estimates the total energy bill for a typical 12-month period is €1,350 for electricity (which covers space heating) and €150 for gas cooking. She says her spend on wood for the stove so far has been negligible. Airtightness (at 50 Pascals, post-retrofit): 4.69 air changes per hour or 5.395 m3/hr/m2 at 50 Pa GROUND FLOOR Before: Uninsulated. Entire ground floor was excavated to accommodate new floor buildup. After: 120 mm Xtratherm XT/UF with thermal conductivity of 0.022 W/mK under a 50 mm screed for underfloor heating. U-value: 0.130 W/m2K WALLS Before: Uninsulated 325 mm brick walls. After: Solid brick 325 mm walls were retrofitted internally with a 50 mm air cavity & Solitex breather membrane followed inside by 140 mm timber stud @ 600 cc filled with 140 mm rigid Knauf Frametherm (0.035 W/ mK), Intello membrane, 20 mm service cavity with battens at 600cc, 12.5 mm plasterboard and skim finish. U-value: 0.225 W/m2K ROOF Before: Uninsulated attic. After: Ceiling joists to main roof is fitted minimum 300 mm Knauf Earthwool (TC = 0.044W/mk). U-value: 0.130 W/m2K. Cold roof space above. Extension floor: 150 mm concrete slab with 120 mm Xtratherm XT/UF with thermal conductivity of 0.022 W/mK under a 50 mm screed for underfloor heating. U-value: 0.130 W/m2K Extension walls: 100 mm brick with 150 mm Xtratherm Cavitytherm (0.021 W/mK)

insulation to cavity, 100 mm block inner leaf, 20 mm service cavity with battens at 600cc and a 12.5 mm plasterboard and skim finish. U-value: 0.131 W/m2K Extension roof: Fibreglass Dryseal roof finish on 18 mm OSB on 120 mm Xtratherm roof insulation (0.022 W/mK) on 150 mm rafters @ 400 cc with 140 mm Knauf Frametherm (0.035 W/mk), airtight membrane, 20 mm service cavity and plasterboard and skim finish. U-value: 0.110 W/m2K New triple glazed windows: Timber aluclad windows & doors from Novus Windows. Overall U-value of 0.82 W/m2K New corner window and slider to extension: Internorm aluclad windows with glass-to-glass joint. Overall U-value of 0.80 W/m2K Roof windows: Fakro DXF thermally broken triple glazed roof windows with proprietary insulated kerb. Overall U-value: 0.70 W/m2K Heating: Daikin Altherma ERLQ011CAV3 air-to-water heat pump. Basia 15 kW & Albaro 14 kW wood burning stoves. VENTILATION Before: No ventilation system. Reliant on infiltration, chimney and opening of windows for air changes. After: Aereco demand controlled mechanical extract ventilation. Water: Rainwater harvesting + low flow fixtures. Kitchen: Cucine Lube kitchen featuring certified 100 per cent recycled wood, F-Four Star certified low formaldehyde content, and are Greenguard Gold certified – a standard set to minimize levels of volatile organic compounds (VOCs) emitted by furniture, surfaces, and paint, as well as other harmful chemicals in indoor environments.

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IN BRIEF Building: 8,952 m2 secondary school Build method: Cross-laminated timber with concrete ground floor Site & location: Sutton, South London Standard: Passive house certification pending

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With a decade of experience designing primary schools to the passive house standard under their belt, Architype have now designed the UK’s first passive secondary school — and all of the evidence suggests there is no better way to ensure a healthy, comfortable environment that is supremely conducive to learning. Words by David W Smith

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everal of the most forward-thinking local authorities in the UK have been adventurous enough to build passive standard primary schools in recent years. But no authority boasted a passive secondary school until Sutton Council opened the £40 million Harris Academy Sutton, in South London, last summer. Not only is it the UK’s largest passive school, but it appears to be the largest school project anywhere in Europe to achieve the standard. The four-storey building covers more than 10,000 m2 and will house 1,275 pupils and 95 staff. It won Building Magazine’s ‘Building Performance Award’ for 2020. The hope is that the project’s success will break down barriers and that it will serve as a template for more passive secondary schools. There has already been intense interest from local authorities all over the UK, and architects Architype are now working on several new secondary schools to the passive house standard. “Risk has been an inhibiting factor for local councils. Until Sutton Council took the leap, they all hesitated to be the first to build a secondary school passive house,” said Architype project architect Christian Dimbleby. “But we’ve proved it’s possible to design large high performing buildings with low carbon and great aesthetics. There can be a little bit of extra cost — between 4 per cent and 8 per cent — but it comes back in the long-term running costs and improvements.”

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Sutton Council’s pioneering approach emerged out of its long commitment to high environmental standards for public buildings. The council created the much-praised BedZED ‘eco-village’ housing project and it drew up ambitious sustainability targets as the first ‘One Planet Living’ council in 2009. Those plans were recently updated with even tougher targets. Sutton Council has put in place stringent requirements, too, for public buildings of more than 1,000 m2. Most London authorities settle for BREEAM Very Good, but Sutton Council has mandated BREEAM Excellent. In recent years, however, the council has become somewhat disillusioned with BREEAM. “It doesn’t dictate the design approach and we were not always satisfied projects were performing as well as they should in practice,” said Adam Whiteley, senior project manager for Sutton Council. “We felt it

Flexibility is there for future styles of teaching to change and develop.

would be easier to monitor a passive house building’s performance and we expected a higher standard.” There was another important motivation behind the decision to go down the passive route. Harris Academy Sutton was the first building to be constructed on the £350 million London Cancer Hub development, which will have 280,000 m2 of medical buildings and research centres. The Cancer Hub will house more than 275 scientists who are developing new drugs and treatments. Sutton Council is the landowner of the site and has a regeneration partnership with the Institute of Cancer Research. The Harris Academy Sutton places a strong emphasis on the sciences and there are many opportunities to collaborate with cancer researchers. “Because our school is a gateway project for the London Cancer Hub, we wanted the architecture to make a real statement. It had to represent much more than the average building by virtue of its high energy performance, building physics and aesthetic appearance,” said Adam Whiteley. Sutton Council’s partnership with Architype is built on their shared commitment to sustainability. Architype have designed passive certified schools in Wolverhampton and Wales, and Sutton Council had already appointed them in 2014 to design the smaller Hackbridge Primary to the passive house plus standard. In January 2016, Sutton asked Architype to carry out a feasibility study for a large secondary school. At the end of the year,

Photos: Jack Hobhouse / Architype | Drawings: Architype Professional site photos: Peter Langdown / Willmott Dixon


Architype submitted a planning application. But there were concerns about the impact of an imposing four-storey building on adjacent low-rise homes and the Architype team was asked to redesign some elements. “We had to accept the east-west classroom arrangements needed some adjustments as they created overshadowing of school courtyards and residential housing,” said Dimbleby. “We designed three iterations to deal with their concerns and finally got planning permission following consultations, revisions and public meetings, on 31 August 2017. The completed building steps down in scale to two storeys on the north side as it gets closer to the houses. It’s much less imposing now. And we’ve designed terraces with green planting that step the roof back and camouflages the main building.” Four months later, in December 2017, work began on site to bring Architype’s designs to life. A few months later, however, more modifications had to be made to the design after the government selected Harris Academy to run the school. The academy requested clearer views into the classrooms. “They wanted the head teacher to be able to walk around and see into the classrooms from the corridors. The idea was to encourage ‘mature’ attitudes to learning,” Dimbleby said. Harris Academy also expressed a desire for Architype to create flexible classroom spaces with removable internal walls. “If the worst came to the worst and we had constant Covid-19 for years, we could take away some walls to double the size of spaces and allow more social distancing. That flexibility is there for future styles of teaching to change and develop,” Dimbleby said. The school, he says, is designed rather like a modern campus. Pupils are given freedom to move around and the cross laminated timber walls are very exposed. “It looks like we’re inviting pupils to graffiti them, but the head wants the students to learn to respect the loveliness of the environment rather than worrying about the consequences. It’s about

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assuming the best in people,” Dimbleby said. An overarching goal of the design, he says, was to maximize the amount of light reaching the courtyards and buildings. To increase solar gain without a risk of overheating, Architype placed most classroom spaces in the north-south orientation. For east-west classrooms, they used vertical aluminium to provide as much shading as possible. Douglas fir fins with aluminium cladding project past the buildings, and the 350 mm deep windows are set back. Meanwhile, Lamilux roof lights allow daylight to flood into the corridors and gymnasium. The school has a concrete ground floor, but Architype used 50 per cent GGBS, a low embodied carbon cement substitute, made from a steel industry by-product. A concrete ground floor was needed because the level of the site changes from one end of the building to the other by a height of one storey. The concrete ground floor serves partly as a retaining wall, and together with the first-floor slab it provides a platform on which to construct the cross laminated timber (CLT) structure above. “We tried to eliminate concrete as far as possible, but we needed it there and round the staircases for fire purposes, especially since we were designing in the aftermath of the Grenfell Tower fire,” Dimbleby said. The CLT made the building much lighter though, enabling Architype to reduce the depth of the foundations. “We were able to get rid of pile foundations and just use mass footings on a concrete raft with occasional foundation strips. Reducing the load by using CLT also helped with airtightness and thermal insulation detailing on the ground as we didn’t need to go through the pile founda-

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tions,” he said. Architype’s own analysis revealed that the switch from concrete to timber for the upper floors reduced the embodied carbon from 863 kgCO2e/m2 to 698 kgCO2e/m2, which is a 20 per cent decrease. Dimbleby said this was “very significant” and the final figure is close to the RIBA 2025 target of less than 650 kgCO2e/m2. The contractor Wilmott Dixon had previously delivered one of the UK’s largest passive house projects, the George Davies Centre at the University of Leicester. But none of the workers from its supply chains had prior experience of passive house construction. Wilmott Dixon sent all the sub-contractors on a two-day passive house introductory course while its own site managers did certified passive house tradesperson training. Even the Wilmott Dixon project lead Graham Thompson knew little about the passive house standard when he joined the project four months into the build. Nevertheless, Thompson has a passion for green building, and had spent a lot of time studying low carbon and energy standards. It turned out Wilmott Dixon made a shrewd choice. Despite his previous inexperience with passive buildings, Thompson’s work on the Harris Academy Sutton earned him a nomination for the Chartered Institute of Building’s 2019 construction manager of the year for schools. He was praised for his “pragmatic, disciplined and strategic” approach. “My first impression was that passive house can’t be that difficult. I thought it must be just another building standard like BREEAM. Within 48 hours, I realised it was like nothing else I’d done before,” said Thompson.

“It’s not rocket science. But it’s different to BREEAM, which I see as a box-ticking exercise. It’s more about designing the core of the building as green and high performing. Having done one passive [building], I’m passionate about them. I think it’s the best method available for anyone serious about the climate. If we made it mandatory for every public building it would have a huge impact, but our industry is slow to react.” Thompson’s perfectionist approach to construction was evident in his decisionmaking. For example, he wanted the timber cladding to be manufactured on site because checks could be done on the spot and it was easier to guarantee precise measurements. Then, he instructed his team to build a full-size mock-up of a section of the building, including two large classrooms. This allowed rigorous testing to be carried out to reduce the risk of errors and formulate quality standards. The mock-up contained all the important elements, including windows, cladding junctions, waterproof seals and walls. It was airtightness tested, and produced a result of 0.3 air changes per hour, which ended up being the same value as the final building too (the airtight layer was toward the outside of the construction, for example being provided by the breather membrane for the CLT walls). Sutton Council used a design-and-build contract, which can be notoriously tricky for quality control if there’s an absence of dialogue between parties. But Thompson instigated a “no blame” culture of open communication. Whenever anyone encountered a problem, they were encouraged to walk into the large site cabin office and ask for a meeting with all key decision-makers.










1 Laying the XPS insulation under the ground floor; 2 cross-laminated timber walls on the upper floors; 3 installing the exposed timber roof beams for the sports hall; 4 low thermal conductivity Ancon TeploTies visible here protruding through foam insulation before installation of brick cladding; 5 & 6 JJI joists installed to upper floor wall over pro clima Solitex Fronta Quattro vapour control membrane, before being finished with a rendered board.

“With D&B contracts you sometimes never see the client again, but Sutton Council were present at all the meetings. And Wilmott Dixon wanted the architects involved every step of the way. So, although we switched from a partnering agreement with Sutton to a D&B contract, everyone was still working as if it was a partnering agreement,” said Dimbleby. The final building has been open since September 2019 and Adam Whiteley and his team have been closely watching its performance. “We’ve tweaked a few things with the on-site teams, but we’re delighted with the performance. As well as the energy and carbon being saved, we’ve had a lot of feedback about how comfortable the school is,” he said. “That was important to us because there’s been a lot of poor-quality school construction over the past two decades. Many school buildings are so poorly designed that they’re

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either overheating, or too cold. It has a negative impact on children’s education, whereas we think the comfort of passive house will benefit them.” Chryssa Thoua, an architect and researcher at Architype, is studying for a PhD on how schools perform, including the influence of the environment on learning outcomes. Dimbleby said that her analysis of data from four primary schools shows that passive house is the only construction method that achieves the CO2 concentration levels required by BB-101 (Building Bulletin-101), which provides guidance on air quality for schools. (See our in-depth feature on Thoua’s research, and on ventilation in schools, elsewhere in this issue of Passive House Plus). “There’s an established link between CO2 and fatigue. The BB-101 requirement is 1,500 parts per million and, in winter, passive houses hover around 700 to 1,200, whereas naturally ventilated normal buildings range up to 5,000 parts per million. At that level, you get issues with concentration and it can be a health hazard,” Dimbleby said. Throughout the year, mechanical ventilation with heat recovery provides fresh air, and there are CO2 sensors in all rooms at Harris Academy Sutton. In the winter, the system delivers fresh warm air. This combination of CO2 sensors to measure air quality, and warm fresh air, is also likely to be a good way to mitigate spread of Covid-19 (again, see our schools and ventilation feature for more). Classrooms never get stuffy and there are no uncomfortable draughts or cold spots. “Unfortunately, public buildings are rarely assessed in terms of energy performance, let alone suitability for learning. But we’re providing bigger and bigger catalogues of evidence showing the benefits of the passive house standard for school buildings,” Dimbleby said.


SELECTED PROJECT DETAILS Client: London Borough of Sutton Architect: Architype Main contractor: Willmott Dixon Structural engineer: Price & Myers & KLH with Rambol M&E consultant: BDP MEP sub-contractors: Jones King & CMB Engineering Electrical contractor: Jones King & DES Group Airtightness testing & consultancy: Etude & WARM Low Energy Building Practice Passive house certifier: WARM Low Energy Building Practice Landscape architect: Churchman Thornhill Finch Quantity surveyor: Synergy Construction and Property Consultants CAD software: Revit Educational consultants: Lloyd Wilson Partnership

Planning consultant: Lichfields Wall insulation: Warmcel, via CIUR Additional wall insulation: Kingspan Roof insulation: Soprema Floor insulation: Kingspan Airtightness products: Ecological Building Systems Thermal breaks (under slab): Foamglas Thermal breaks (external walls): Puren Glazing & shading: Lang Fenster Cladding: NH Ethridge Screeds: Flowcrete Fit-out: DMC Ash Roofing: Soprema Cross-laminated timber: KLH CLT structural engineer: Rambol Main space heating: Ideal, via CMB Engineering Ventilation: Swegon, Lennox & Airflow MVHR units, via CMB Engineering Solar PV: Spirit Solar

There’s been a lot of poorquality school construction over the past two decades.

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ph+ | sutton school case study | 55



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Fo l l o w u s : 56 | | issue 36

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IN DETAIL the school used 18,477 m3 of gas. This converts to 204,444 kWh of gas, using conversion calculation provided by Gazprom, or 23 kWh/ m2 of delivered heat energy. While this was mostly for space heating, some domestic hot water is provided by gas heaters too and use of this may have been above average during 2020 due to increased handwashing. The building may also need extra gas heating in its first few years as it is only partially occupied, and thus has less internal heat gains from occupants. During the same time period the school used 84,480 kWh of imported grid electricity.

Building type: 8,952 m2 (treated floor area) four-storey secondary school (10,625 m2 gross internal floor area) Location: Chiltern Road, Sutton Completion date: August 2019 Budget: £40million / £2,764m2 Passive house certification: Pending Space heating demand (PHPP): 12.65 kWh/m2/yr Heat load (PHPP): 8.91 W/m2 Primary energy demand (PHPP): 133 kWh/m2/yr Heat loss form factor (PHPP): 1.8 Overheating (PHPP): 0 per cent Number of occupants: 1,275 students plus school staff Environmental assessment method: BREEAM – compliance with all mandatory credits required to achieve an ‘Excellent’ rating Airtightness (at 50 Pascals): 0.30 ACH @ 50 Pa Energy performance certificate (EPC): A 22 Thermal bridging: Bespoke details developed to avoid thermal bridges across the external envelope based upon Architype’s experience of delivering passive schools. Where not possible to omit, thermal bridge calculations were done using Psi-Therm & Psi-Therm 3D, e.g. chi-value calculation was done for metal fixings required for large vertical fins. Thermal bridge & temperature checks done for window details & critical ground details. Measured energy consumption: According to its gas meter, over 12 months between November 2019 and October 2020 inclusive,

Energy bills (estimated): Using the school’s Gazprom tariff of 1.172p per kWh and the gas consumption figures above, we estimate an annual gas consumption bill of £2,396, exclusive of VAT & standing charges, or about £200 per month. Note this includes some domestic hot water as well as space heating. Also standing charges can potentially be large – in the one sample bill we viewed from Harris Academy Sutton (June 2020), the standing charge for the month was £328, while the monthly gas usage charge was £117. Foundations: Ground bearing pads and strip footings, thermally separated from the slabs using high compressive strength insulation (100 mm Foamglas). Ground floor: Concrete blinding followed above by 2 x 50 mm XPS insulation (Kingspan Styrozone® N300), 200 mm reinforced concrete slab with edge thickening, liquid applied DPM, carpet/vinyl/lino/timber finish above. U-value: 0.34 W/m2K (typical). Typical ground floor wall: Brick cladding with Ancon TeploTie wall ties or copper sheet on 22 mm plywood backing fixed on Nvelope helping hand bracket on thermal break; followed inside by 50-80 mm ventilated cavity, 100 mm Kingspan phenolic foam board made up of two layers of 50 mm with staggered joints, pro clima DA vapour check and airtightness membrane, concrete columns with timber frame infill (MGO board on 250 mm timber studs with internal 18 mm Medite SmartPly OSB3), 38 mm service cavity insulated with Rockwool RWA45, gypsum board wall lining. U-value: 0.19 W/m2K Typical upper floor wall: 21 mm thick vertical Douglas Fir timber rainscreen cladding, treated with PTG Sentrin FRX, followed inside by insect guard mesh, softwood 50x50 mm battens, pro clima Solitex Fronta Quattro vapour control membrane, 195 mm framed JJI-joist structure filled with blown insulation (Warmcel), pro clima DA vapour and airtight membrane, VersalinerTM magnesium oxide sheathing board, CLT columns with timber frame infill (timber studs with internal 18 mm Medite SmartPly OSB3), 38 mm service cavity insulated with Rockwool RWA45, gypsum board wall lining. U-value: 0.17 W/m2K

Roof: Soprema reinforced bitumen membrane warm roof covering system (front wings have green roof) with tapered (PIR) & 180 mm uniform (EPS) insulation roof boards underneath, followed below by vapour control layer on 300 mm cross laminated timber exposed structural deck. U-value: 0.11 W/m2K (average tapered & uniform insulation). Windows & external doors: Lang-Fenster composite (timber and aluminium) triple glazed argon-filled glazing, windows & external doors. Average overall window U-value of 0.96 W/ m2K (installed). Wicona aluminium glazed doors used for Primary Entrances. Roof windows: 10 x Lamilux CI System glass architecture with PR60 energysave roof lights. Glazing: toughened outer and laminated safety glass inner with low emissivity coatings, gas filled cavities and spacers. Anti-glare obscured glass specified for sports hall. U-value: 1.10 W/m2K Space heating system: 2 x Ideal EvoMax 150 kW condensing gas boilers (one back-up). Radiators in teaching and office areas. Thermostatic valves with remote wall mounted room temperature sensors. Domestic hot water: 26 x localised electric water heaters (various). 2 x domestic hot water calorifiers (Ormandy Rycroft Evoplate CP-B25 + 257 L Buffer Vessel). 2 x gas fired DHW heaters (Andrews Water Heaters - Ecoflo EC230/600). Ventilation: 5 x Swegon Gold RX mechanical ventilation with heat recovery systems in various models, ranging in heat recovery efficiency from 75 per cent to 82 per cent. 1 x Airflow Duplexvent Multi Eco-N DV4500 MVHR. 1 x Lennox LX0412. Kitchen: Dedicated extract system consists of an extract & supply hood connected to volume control dampers. Water: All wash hand basins, classroom sinks, and showers have flow regulators to limit water use. Water wastage from sinks/shower and hand basins is limited by flow control regulator valves on the inlet. BMS system is programmed to monitor the flows on the incoming revenue meter. Electricity: 17 kWp roof-mounted PV array, generating an estimated 10 per cent of the school’s energy needs. Green materials: KLH PEFC-certified cross laminated timber, Douglas Fir cladding all from FSC certified sources, concrete with 60 per cent GGBS content, long-life copper cladding with recycled content, cellulose insulation from recycled newspaper, green roof system, magnesium oxide boards, Tarkett DESSO loose lay carpet tiles, OSMO Polyx Oil.

ph+ | sutton school case study | 57





(estimated, see ‘In detail’ for more) Building: 175 m2 detached dwelling Build method: Timber frame with concrete ground floor walls Site & location: Rural site, Buckinghamshire Standard: Passive House Plus certified

58 | | issue 36




Lark Rise is an elegant new passive house in rural Buckinghamshire designed by bere:architects, but it is more than ‘just’ a passive house. Because it produces and stores so much of its own energy through on-site solar power, it is a certified passive house ‘plus’, and over the following pages, its architect Justin Bere explains how dwellings like this can play a key role in decarbonising our economies and societies in the coming decades. Words by Justin Bere

ph+ | lark rise case study | 59




he powerhouse of the rich world’s economy, since the birth of the industrial revolution, has been the wealth of coal, oil, gas and bountiful minerals torn from the ground without self-constraint; effectively for free and in limitless quantities until it runs out. This is the start of a process that goes on to convert these acquisitions into money-making industrial, domestic and agricultural products that add value, called capital growth. The making of products involves specialist collaborators; each one ‘creating wealth’ which, in the form of salaries and profit, drips off the branches of a ‘magic money tree’ that is politely described as gross domestic product (GDP). Through this process, we have produced more than we need and achieved a result that was lamented by Sir David Attenborough in September 2020: “…human beings have overrun the world.” (Attenborough, 2020 ). Thirty years ago, Wolfgang Feist proved that there is another way to live, when he built three high-performance passive row-houses at Darmstadt Kranichstein. Fundamentally, his solution demonstrated how the fuel supply that maintains our lives can be turned right down to almost nothing, so we can find a niche within nature, using whatever energy is available from the sun and the wind each day. As the need to address climate change grows

60 | | issue 36

ever more urgent, you might think everyone would understand something as fundamentally sensible as the passive house standard to deeply reduce energy consumption. However, for a politician, the idea of expanding off-shore energy infrastructure, “surely no more difficult than mass-producing a car”, would seem much easier to grasp and mandate than the roll-out of deep energy efficiency measures with all their nuances, complexity, sheer hard work and political risk. For the public, too, the cost, complexity and disruption of home-retrofit isn’t nearly as attractive as hearing that the problem will be solved by others in the form of renewable energy production, so life can go on as normal. Indeed, ‘supply more energy’ is a much more exciting concept for most people than the concept of ‘use less energy’. ‘More’ means growth, expansion, opportunity, while we are hard-wired to think of less energy as being synonymous with decline. However, using simple calculations based on UK government ECUK data, it is possible to calculate that to decarbonise all of the UK’s energy consumption without a deep energy-saving transformation of the built environment (taking into account primary energy and the efficiency advantages of heat pumps to heat all our homes, but excluding electrification of transport) we would need to increase

the UK’s offshore wind infrastructure by approximately 12 times its current generating capacity (Bere, 2020). If we decarbonise all sectors and include the electrification of transport, then offshore electricity capacity needs to increase by 16.7 times, along with the electricity distribution network on land. This is surely an inept way to try to decarbonise our lives, yet it’s government policy and the current political discourse in the UK is almost all about the relatively easily-understood notion that we can scale up renewable electricity generation to heat our homes, power our transport and everything else, and if not renewable electricity, then nuclear will ride to the rescue. This, despite, in 2017, a World Bank report which stated that without deep energy efficiency measures, it’s unlikely that the world’s current need for energy can be decarbonised by wind and solar energy, let alone the trend in future energy demand. The report explains that even if we only consider resource requirements, supplying the world’s current energy demand by renewable energy would require a staggering 34 million tonnes of copper, 40 million tonnes of lead, 50 million tonnes of zinc, 162 million tonnes of aluminium and 4.8 billion tonnes of iron. (World Bank, 2017) As the economist Dieter Helm recently



wrote, “…our current economy is staggeringly inefficient. As with the expansion of many economies over the 20th century, our economy has been based on the extraction of non-renewable minerals (including but not limited to fossil fuels) and the devastation of renewable natural capital.” (Helm 2020) But due to evolutionary pressures, our essentially prehistoric brains are hard-wired to want ‘more’, not ‘less’. This personality trait provided our ancestors with advantages for survival. They were living in a world of natural abundance. Only in the last one or two hundred years has greed become a serious threat to survival. The concept of ‘sufficiency’ doesn’t appeal naturally to us. But unless we recognise and learn how to manage what is now a genetic impediment, we seem likely to go extinct before evolution has a chance to phase out and replace this aspect of our brains with something more suited to the 21st century climate emergency. So, we now need to find a narrative to widely and easily capture people’s imagination, turning less into more; perhaps not so much about ‘less consumption’ in our homes as ‘more sharing’. Indeed, de-industrialised countries should arguably be carbon-negative anyway to pay for the consumption of carbon from the manufacture and transportation of imported products, as well as historic emissions. The story of the Bavarian village of Wildpoldsried, a German village that generates 500 per cent more energy than it needs, captured the imagination of people all around the world. This seemed to make the point that to succeed in decarbonising our society, the story of energy efficiency should be no more than the subtext of a grand story about energy generation. As such, the passive house plus standard — which requires buildings to meet the classic passive house standard plus generate a minimum of 60 kWh/m2/yr of renewable energy on site —can be described as nothing less than the birth of a whole new economic solution, replacing the extraction of non-renewable resources by the production and sharing of renewable resources. If homes are mostly self-powered and even teamed up with electric transport, then people might get it. Le Corbusier captured the public’s imagination with the concept of ‘a machine for living’ and the passive house plus standard embodies this concept in the true sense that Le Corbusier might have dreamed about.

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Photos: Peter Cook & Tim Crocker

ph+ | lark rise case study | 61



MONITORING THE PERFORMANCE OF LARK RISE Lark Rise is a split-level dwelling in rural Buckinghamshire, designed by bere:architects and certified to the passive house plus standard. It is of timber frame construction resting on concrete ground floor walls, part of which serve as a retaining wall. The house was built by the owner as a possible future retreat, but in the meantime, it is tenanted. There have been three tenants. The first tenant was a close friend of the owner and occupied the house for a short time. Subsequent tenants have had unusual user habits that have produced some unexpected results. This includes a tenant who ran a hot jacuzzi and two bouncy castles twenty-four seven. They also held some extravagant parties with powerful lighting running the whole perimeter of the garden. Indoor lighting use is much higher than expected, with lights left on throughout the house, and power socket loads running into the early hours on most days. It has been a tough task trying to understand the underlying capability of Lark Rise in the event that occupancy patterns were closer to our expectations. Further, the output of the solar panels at Lark Rise has been less than expected, which may be due to some overshadowing from adjacent woodland that rises to the south of the house. But our next passive house plus dwelling, The Brambles, was occupied in March 2020, and we are monitoring its performance in parallel with Lark Rise. The solar panels at The Brambles are performing as expected, and the owners are occupying the house in a much more sympathetic way. The Brambles results are very much better than at Lark Rise. For example, while in September Lark Rise generated over 2.5 times as much energy as it imported from the grid, over the same time period The Brambles generated 70 times as much energy as it imported. We will have collected and processed a year’s worth of data for The Brambles by next April and look forward to publishing them in full next summer.

SELECTED PROJECT DETAILS Architect: bere:architects M&E engineer (heating & ventilation): Alan Clarke M&E engineer (solar, battery & self-consumption study): Energelio Renewable energy consultant: Graham Taylor, Reduce Ltd Civil & structural engineering: Techniker Quantity surveyor: Andrew Turner & Company Timber frame: Kaufmann Zimmerei und Tischlerei Lighting designer: EQ2 Main contractor: Sandwood Design & Build Airtightness testers: Paul Jennings & BRE Groundworks: C Putnam & Sons Ltd Wood fibre insulation: Steico Foamed glass wallboard: Foamglas PIR insulation: Bauder Floor insulation: Kingspan Airtightness products: Ecological Building Systems Windows & doors: Bayer Schreinerei Frameless internal doors: Contrax Porcelain tiles: Domus Green roof: Bauder Air source heat pump: Viessmann MVHR: Paul Novus, via Green Building Store Solar PV array: Darke & Taylor Ltd Wastewater treatment system: Anua International Wastewater treatment consultant: Nick Grant Passive-certified chimney: Schiedel Passive-certified stove: Morsoe

62 | | issue 36

We can find a niche within nature, using whatever energy is available from the sun.



CONSTRUCTION IN PROGRESS PASSIVE HOUSE OR PASSIVE HOUSE PLUS? Let’s assume that the logic for energy efficiency is established. Why might we consider the passive house plus standard — which demands 60 kWh/m2/yr of onsite renewable energy generation — as a better solution than classic passive house? We all like simple solutions. Who wouldn’t want to keep things simple if possible? Passive house is already hard enough, so why would we make life more complicated (and resource intensive) with passive house plus? This question can be considered in two ways; one is physical and the other psychological. 1. Reduced grid-demand (overall quantity and peaks) and balancing supply-and-demand: Supply in a decarbonised renewable electricity grid is affected by variable meteorological factors, so there’s an inevitable mismatch between supply and demand. Although delivery-side lithium batteries are being tested by the National Grid, there are clearly resource issues surrounding the adoption of this technology at such a scale. If as a society we insist that the problem of balancing a renewable energy grid is a service-provider’s responsibility, then we may force the grid to invest huge resources in large-scale battery storage, inefficient hydrogen-storage, methane production, or expensive short-life and dangerous nuclear power plants to provide ‘base-load’. So, we either need the national grid to store renewable electricity for us, as a kind of public service, and then urgently supply it whenever our homes cry out for it, or else we can design our buildings to demand-shift. The fabric of a passive house enables demand shifting of heat, even in periods of prolonged cold weather, and domestic hot water thermal storage can also help (by increased storage capacity and increased tank temperature). Despite this, a classic passive house does require a much more consistent supply of energy than a passive house plus, particularly if the latter has a battery. Furthermore, evidence is emerging that an all-electric passive house plus has lower peak electrical demand than an ordinary house (figure 1, page 65) or a classic passive house, and approximately 25 per cent of the annual grid-energy demand (figure 2, page 65). To understand the significance of these emerging results, we need to first recognise that contrary to popular understanding, renewable electricity produced from offshore and onshore wind and solar is a tiny component of the UK’s current all-sector energy mix. It is a precious commodity that supplies 4 per cent of the UK’s current annual all-sector energy needs (and a lower percentage if we include, as we should, the massive impact of the off shoring of UK manufacturing).

If the national electricity grid is to be scaled up to provide 100 per cent renewable electric home-heating to buildings that are not retrofitted, offshore wind and solar will need to be increased by 12.6 times its current capacity, and if in addition the national grid is to supply 100 per cent renewable electricity for the electrification of UK’s current transport requirements, offshore wind and solar will need to be increased by 16.7 times. (Bere, 2020, see calculations at Crucially, initial monitoring results from passive house plus dwellings indicate that rolling out the passive house and passive house plus concepts at scale for retrofits and new-builds may have the potential to make decarbonisation of the grid achievable without the need for a gigantic increase in renewable energy infrastructure and associated storage, or such a massive renewal of national grid transmission network cables. If we can more or less eliminate UK home-heating; and if the demand-shift characteristics of the passive house plus standard are shown to help absorb peak winter renewable electricity spikes, and if (crucially) passive house plus can help avoid peak electricity demand spikes (typically early evening in winter); then here is a way to make decarbonisation of the grid realistically achievable. Once we have the results of 12 months of monitoring data for The Brambles, our second passive house plus, we hope to use this data in a recently-created dynamic model of the UK’s energy system that is currently being used to test renewable electricity grid scenarios for the UK Department of Business, Energy & Industrial Strategy. If it is established by this means that the passive house plus standard offers the most resource-effective way to decarbonise a renewable energy grid, there would be an argument to provide grant aid to ensure that the benefits are available to everyone. We agree with those who worry about a society where the privileged few have access to an advanced, beneficial technology, and we believe that the way to overcome this is to establish the national benefits of adopting an advanced retrofit and new-build system, integrated into all the UK’s homes. Such an approach might provide return-on-investment and economic advantages, health, safety, durability, reliability and long-life benefits. It might also be the only realistically achievable solution. 2. A captivating idea: We need a captivating vision for sustainable living that resonates deeply with human instincts. The community-wide advantages of using a particular breed of long-life, plus-energy, all-electric home to perform critical and transformative services, i.e. the passive house plus, could provide this vision.




4 1 Work begins on foundations; 2 only a partwidth of the slab was installed first to retain access; 3 reinforced concrete going up, still with only a part-width slab; 4 the mixed-construction house features a 50 % GGBS concrete structure on the lower floor, with a prefabricated timber frame upper floor.

ph+ | lark rise case study | 63



Join us on the road to sustainability 0 Book your CPD today. Email 64 | | issue 36


+353 1 678 1800 |



CONSTRUCTION IN PROGRESS THE PERFORMANCE OF A PASSIVE HOUSE PLUS WITH BATTERY The emerging evidence appears to suggest that there are two distinctive performance characteristics of a passive house plus, where it also has a battery rated at approximately 1 kWh per 1 kWp of PV array (this is considered the cost-optimal ratio for self-consumption). A university research collaboration is planned to study the first year’s data from The Brambles, our second passive house plus dwelling, in order to test what should, strictly speaking, be considered just a hypothesis at this stage.


1. Potential for more than 80 per cent reduction in peak demand of electricity per home, compared to a conventional home or classic passive house. This is because peak electricity demand, usually early evening on a winter’s day, can be supplied by the battery to avoid contributing to a spike on the grid; this can be derived from a base level of retained electricity storage, or by pre-charging from a flood of excess renewable energy. Reduced peak-demand is important because the peak demand of each home is aggregated with others to determine the required total national electricity generating capacity to meet peak demand ‘triads’ (the three half-hour periods annually during which electricity demand is highest), and the amount of energy storage that will be needed somewhere in the system for when renewable energy isn’t immediately available. 2. Potential 75 per cent reduction of annual electricity demand from the national electricity grid of an all-electric passive house plus with battery, compared to an all-electric classic passive house (and up to 94 per cent reduction in annual metered energy demand from gas and electricity when compared to a typical UK home, as derived from ECUK data). Potential to produce approximately ten times as much renewable energy in a year as the building imports from the grid, and the potential to export over twice as much renewable electricity to the national grid or a local microgrid in a year, compared to its own use. This performance has not been achieved at Lark Rise due to unusual user occupancy, but performance so far at The Brambles does support the results shown in the graph (figure 2).



Figure 1 We can see here that compared to a classic house, the Lark Rise project with a 15kWh battery reduces its peak load demand by more than 80 per cent. 20,000 15,000

3869 Grid Electricity





13606 Gas 1000 Grid Electricity 3000 Solar Direct & via Battery

4014 Grid Electricity


-8000 Solar Export to Grid


1 Lignotrend prefabricated acoustic roof beams and (inset) end panel; 2 installation of the Bayer triple glazed windows; 3 installing the Bauder bituminous membrane before the green roof goes in; 4 the timber frame features 22 mm Austrian larch cladding externally.


Typical UK House

Typical UK Passive House

Typical UK Passive House Plus with 13kWh Battery

Figure 2 Relative energy demand of typical and passive house dwellings

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Sustainable change is in the air

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66 | | issue 36



IN DETAIL Building type: 175 m2 detached two-storey mixed-construction family dwelling Location: Buckinghamshire, UK Completion date: October 2015 (house completed) / May 2018 (solar PV installed) / August 2019 (battery installed) Budget: Confidential Passive house certification: Passive House Plus certified Space heating demand (PHPP): 14.5 kWh/m²/yr Heat load (PHPP): 11 W/m² Primary energy demand (PHPP): 80 kWh/m²/yr Primary energy renewable (PER demand): 37 kWh/m²/yr Primary energy renewable (PER generation): 79 kWh/m²/yr Heat loss form factor (PHPP): 2.1 Overheating (PHPP): 5 % of the year above 25C Number of occupants: 2 Airtightness (at 50 Pascals): 0.40 air changes per hour Energy performance certificate (EPC): A Measured energy consumption (Aug 2019 to Aug 2020, solar energy generation minus net grid consumption): - 32 kWh/m²/yr for all uses including domestic hot water, heating, lighting & all appliances. Imports from grid: 21 kWh/m²/yr Solar generation: 40 kWh/m²/yr Exports to grid: 13 kWh/m²/yr Net grid consumption: 8 kWh/m/yr (Note: appliances include old Aga kettle inefficiently heated on induction hob instead of

standard electric kettle & lighting is used during the night until the early hours of the morning on most days. User occupancy patterns have adversely affected results, but we are finding the performance of The Brambles passive house plus is significantly better than Lark Rise – see main text). Energy bills (estimated): From August 2019 to August 2020, 3,801 kWh imported from grid. Using the cheapest available tariff suggested by, at 15p per kWh, equals £570 plus standing charge of £58 (16p per day x 365) for a total of £628, plus 5 % VAT equals £659 per year. Over the same time period Lark Rise exported 3,801 kWh to the grid, at 4.92p per kWh makes for an estimated feed-in-tariff of £1,098, and an estimated net profit on energy bills of £439 per year. Thermal bridging: The concrete retaining wall structure was externally wrapped in insulation to avoid thermal bridging and maximise the available thermal mass. Wall-wall ground (horizontal) externally insulated concrete retaining wall: -0.0614 W/mK; wall-wall ambient (horizontal) externally insulated concrete retaining wall: -0.0603 W/mK; wall-wall ambient (horizontal) timber frame wall: -0.0372 W/mK; wall-wall ambient (horizontal) timber frame wall: -0.0559 W/mK; wall-wall ambient (horizontal) timber frame wall: -0.0455 W/mK; wall-wall ambient (horizontal) timber frame wall: -0.0449 W/mK; wall-roof (vertical) timber frame wall & roof: -0.0195 W/mK; wall-roof (vertical) timber frame wall & roof: -0.0284 W/mK Ground floor: 50 mm sand blinding at base followed above by 410 mm foamed glass insulation below-slab, waterproof membrane, 300 mm 50 per cent GGBS concrete slab, vapour barrier, 35 mm PUR insulation, 67 mm screed. U-value: 0.082 W/m2K

cent GGBS concrete basement retaining structure. U-value: 0.107 W/m2K Upper ground floor: Prefabricated timber frame with 22 mm Austrian larch cladding externally, followed inside by 25 mm counter-battens, building paper, 16 mm vapour-permeable fibre board, 260 mm softwood posts with 260 mm Rockwool insulation, 15 mm OSB panels, vapour barrier, 40 mm service cavity filled with mineral wool and 12 mm plasterboard internally. U-value: 0.137 W/m2K. Roof: 120 mm extensive green roof externally on a multi-ply, hot-melt bituminous membrane layer, followed underneath by 280 mm foil-faced PIR insulation, vapour barrier, prefabricated glulam box-beam ceiling (Lignotrend system). U-value: 0.074 W/m2K Windows & external doors: Bayer triple glazed windows with laminated larch-Puren frames, argon-filled units with U-value 0.6 W/ m2K, g-value 0.62 and whole-window U-value mostly of 0.7 – 0.8 W/m2K. Heating system: Viessmann VITOCAL 242-S combined air-to-water heat pump and 12.4 kWp photovoltaic array supplying integral 220 litre domestic hot water tank and underfloor heating. Ventilation: Paul Novus 300 heat recovery ventilation system. Passive House Institute certified to have heat recovery rate of 93per cent. Water treatment: On site waste-water treatment using an Anua septic tank with Puraflow water-polishing

WALLS Lower ground floor (exposed): Austrian larch cladding externally with 360 mm wood fibre insulation on 250 mm 50 per cent GGBS concrete structure. U-value: 0.118 W/m2K

Electricity: 38 x Sunpower Panels + Fronius Primo 3.6 & 8.2 kW inverters with 12.4kWp output and export limiter (requirement of energy supplier). In 2019, the troublesome export limiter was removed and replaced by a newly released Fronius integral digital export limiting upgrade on each inverter and the newly released Tesla Gateway changeover switch.

Lower ground floor (buried retaining wall): 360 mm exterior foamed glass insulation on waterproof membrane, on 250 mm 50 per

Green materials: All timber is untreated and sustainably sourced. All interior finishes are non-toxic and VOC-free.

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Contemporary Vernacular Passive House, Co. Cavan Architect: Niall Smith Architects Air Pressure Test Result: 0.39 AC/H @ 50 Pascals Specific Heating Demand: 11 kWh/m2/year U Value for Walls: 0.11W/m2K

Ecological brands used: Gutex, Pro Clima, Bosig, Wellhöfer, Auro, Thermafleece

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Proper ventilation has been recognised as an important quality for school buildings at least since the Victorian era. But, in the current pandemic, have we lost sight of the role of ventilation?

Words by Anthea Lacchia

Oakmeadow passive primary school, Wolverhampton


rchitects at leading sustainable design firm Architype have long been thinking about how to ensure good air quality in schools. Mark Lumley, associate director at Architype, oversaw the delivery of the first passive-certified schools in the UK in 2011. But the firm’s work and research into school building design started even before that, with the delivery of two primary schools — St Luke’s and The Willows — in Wolverhampton in 2008 and 2009. “We worked to deliver them as sustainably as we could,” Lumley said. This involved careful consideration of building fabric, and super insulation of the buildings through triple glazing and building orientation, as well as the use of cross ventilation to secure good air flow. “We used non-toxic materials as much as possible,” said Lumley. This included natural paints and finishes, timber in the construction, and recycled newspapers in the insulation. These two schools served as an example of “strong ideological principles put into practice,” he added. Evaluation of the schools, once they were occupied, identified certain elements of the

Photo by Leigh Simpson Photographer

building structure and performance that could be improved, such as the presence of cold bridges in the structure, as well as elevated CO2 levels inside. “There were various areas in which we felt we could improve our delivery, and that’s when the practice became aware of passive house and all it entails,” said Lumley. To ensure better air quality and better performance of the buildings, Architype adopted the passive house standard for its next two primary schools, Oak Meadow and Bushbury Hill, which were built for Wolverhampton City Council in 2011. This led to the commission of Wilkinson Primary in Wolverhampton, completed in 2014, also to the passive house standard. A subsequent program of post-occupancy research, run in association with Coventry University, compared the performance of Architype’s non-passive schools with the first and second generation of its passive schools, as well as with a school built in the 1970s and not designed by Architype. The research, conducted in four classrooms in each of the six schools over one year, included monitoring CO2 levels as a proxy for

ventilation rates and air quality, measuring humidity and temperature levels, observing blind usage and window opening behaviour, as well as assessing teachers’ and children’s perceptions of their environment, such as satisfaction, through questionnaires. One of the researchers involved in this program was Chryssa Thoua, an architect who is currently completing her PhD at University College London in collaboration with Architype on a different project. The results were clear. Passive-standard schools performed better across all the measurements. “Temperatures were more stable in the more recent passive house schools, and ventilation rates were higher in the passive house schools,” said Thoua. “The difference was really stunning when comparing the results with the conventional school from the 1970s,” she added. “There was a little bit of overheating in summer in the earlier passive house schools,” commented Lumley, “but nothing like the overheating you get in some of the non-passive house schools, so overall the fabric was doing what we wanted it to and the energy bills were incredibly low.” Since 2014, Architype has delivered further passive-certified primary schools, as well as the first passive house secondary school in the UK – Harris Academy Sutton, which is featured in this issue, the latest in a long list of Architype schools to be published in Passive House Plus. The impact of architects’ decisions on the

One way of mitigating the risk of transmission is to equip schools with CO2 monitors.

ph+ | schools insight | 69



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Indoor Environment / Indoor Air Quality / Winter

above Monitored CO2 levels in several Architype-designed schools - including pre passive and two generations of passive house designs - along with a conventional 1970s school.

environment has been a constant consideration throughout Thoua’s career. “I think a lot of architects have the sense that, in order to build something, you have to destroy something else. So you have to tread very lightly,” she said. “Indoor air quality and the indoor environment play a significant role on children’s health, development, academic performance, concentration and memory. Different studies have shown again and again how important it is to maintain good indoor air quality and a good environment in schools, and it is a matter of social justice as well,” she said, stressing that, as designers, “we have to make sure we get it right”. Her current research aims to understand more about indoor air quality and thermal conditions in passive-standard primary schools in the UK, and to develop a framework for assessing indoor air quality in schools. While CO2 levels act as a good proxy for occupant-related air pollutants, Thoua told Passive House Plus that she wanted to provide a more comprehensive assessment of indoor air pollutants and air quality in schools. Using indoor and outdoor sensors in a sample of classrooms over one year, she

St Luke's low energy primary school

measured parameters such as temperature, relative humidity, and pollutants such as CO2, nitrogen dioxide, particulate matter, total volatile organic compounds (which can be emitted by materials such as paints and adhesives) and carbon monoxide. These measurements were coupled with observations in the classrooms. Given that this research is based on case studies in four schools, “we can’t generalise too much,” cautioned Thoua, but results to date indicate that, on average, ventilation rates (estimated from CO2 levels) in the passive-standard schools were higher than those reported in previous studies in primary schools in the UK, and there was no overheating in summer, taking into account outdoor mean temperatures. “We also found that in winter, the average daily minimum temperature [in the passive schools] was above 19°C in all classrooms.” she said. This is in line with current guidance, though in reality temperatures in regular classrooms often drop below this in winter. Thoua’s research is ongoing, as she continues to assess the correlations between the measurements and different building characteristics, in an effort to propose effec-

Photo by Leigh Simpson Photographer


tive strategies for managing indoor air quality in schools. Being mindful of the air inside school buildings is critical in the context of Covid19, with ventilation playing a key role in mitigating the transmission of this disease, said Professor Jose L Jimenez, a fellow at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder. While we don’t yet have published studies on the impact of passive house design on Covid-19 transmission, the need for good ventilation is well-established in the scientific literature, and in policy advice relating to Covid-19. Jimenez, who is studying the transmission of Covid-19, is one of the authors of a recent study which highlights how singing indoors, unmasked, can spread Covid-19. Since the start of the pandemic, several super spreading events involving SARS-CoV-2, the virus that causes Covid-19, have occurred during choir practices. Such events highlight the importance of following public health advice, including the use of face coverings, hand washing and social distancing. They also tell us something about how the disease can be transmitted. Scientific research on Covid-19 is moving at a very fast pace, and, as a result, our understanding of this new disease is constantly evolving, with updated guidance and advice from national and international public health experts following suit. However, Jimenez told Passive House Plus, the evidence for airborne (through the air) transmission of Covid-19 is now “overwhelming, and it has been overwhelming for quite some time.” “When people talk, aerosols are between 100 and 2,000 times more important than droplets. There are two situations in which the disease is transmitted: one is when you talk in close proximity to someone […], especially without masks indoors or outdoors. The second situation is when you share indoor air in a room with someone who’s infected for a long time, meaning at least 30 minutes, to an hour or several hours. That’s when we see these super spreading events,” he explained. If you imagine the virus as inside smoke, “smoke is very concentrated in front of the smoker, but it can fill a room with time,” he said Jimenez. Jimenez is one of 36 scientists who wrote an open letter to the World Health Organisation in July, asking it to recognise the airborne spread of Covid-19, and to revise its recommendations. The letter is signed by 239 scientists and is published in the journal Clinical Infectious Diseases. It cautions against overcrowding and calls for ventilation measures to include “a clean supply of fresh, outdoor air” and to “minimise recirculating air”. Another signatory is Professor John Wenger from University College Cork, who studies the chemistry of the atmosphere, including the chemical and physical properties of aerosols. “Aerosol or airborne transmission is really an important way that the virus is spread, and it’s been kind of ignored,” he told Passive House Plus. “Masks are one of the best defences we

ph+ | schools insight | 71



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Editor’s view Opening windows only a short-term solution

Bushbury HIll passive primary school, Wolverhampton

have against spreading and also receiving the virus,” said Wenger, “but the next thing we really need to think about is ventilation. The focus has been very much on being close and also cleaning surfaces, but we need to clean the air as well.” This has important implications for how we ventilate our classrooms. Simply opening the windows five minutes every hour doesn’t work, said Jimenez. One way of mitigating the risk of transmission is to equip schools with CO2 monitors, to measure CO2 as a proxy for ventilation and for the amount of virus in the room, said Wenger. CO2 monitors with a traffic light system, which are equipped with non-dispersive infrared (NDIR) sensors, are cost-effective and can help remind teachers to act by opening windows when levels get too high (usually above 800-1,000 ppm), said Wenger. Jimenez agreed that CO2 sensors are essential but recommended keeping the CO2 level “below 700 ppm at all times”. However, “a low level of CO2 doesn’t necessarily mean that your ventilation is good,” cautioned Dr Chris Iddon, chair of the CIBSE natural ventilation group. This is due to the time it takes for CO2 to build up in a space, which will vary according to room size and the number of occupants, he explained. Iddon also pointed out that there is still a lot we don’t know about Covid-19, including the dose of virus required to infect someone. In addition, the amount of aerosols that someone might release can vary by several orders of magnitude, he said. CISBE’s current guidance on ventilation in the context of Covid-19 recommends “ventilating spaces as much as reasonably possible with outside air as one measure to reduce transmission risk.” It also states that, “CO2 concentrations regularly greater than 1500 ppm are indicative of poorly ventilated spaces.” This advice is consistent with that of the UK government’s environmental and modelling group, part of SAGE (Scientific Advisory Group for Emergencies), published in October. As well as tackling the immediate crisis posed by the pandemic, installing good ventilation systems in schools would ensure “a healthier environment for everyone, better academic performance, and hopefully better energy efficiency as well,” said Wenger. The type of ventilation employed may

Photo by Leigh Simpson Photographer

depend on what is achievable in the short and longer term. In the short term, we may be forced to rely on opening of windows — preferably with CO2 sensors — as a means of mitigating airborne transmission risk, said Wenger, but in the future the design of appropriate ventilation systems in schools is essential in ensuring air quality. “In the short term, it’s going to be very difficult, I would say, to roll out proper ventilation across all the schools. But in the medium term, it’s something we should really look at. Because there are going to be big benefits,” he said. “If we have proper ventilation in classrooms, there will be less spread of things like cold and flu so it will maintain a healthier environment for everybody. We’ll also have improved academic performance and hopefully better energy efficiency too.” Chris Iddon said that natural ventilation can work if done correctly. “Natural ventilation openings don’t have to be fully open or fully closed,” he explained, suggesting a balance can be struck between comfort and ventilation. “There are several systems out there that will mix the air to temper it before delivering it.” While mechanical ventilation in passive house schools presents advantages, people also need to understand how to operate the system, he said. Air filtration is also “very important,” said Wenger, cautioning that any recirculated air needs to be filtered and filters need to be changed regularly. Jimenez and Wenger agreed on the effectiveness of portable HEPA (High Efficiency Particulate Air) filters, which can be plugged into the wall, in mitigating the transmission. Temperature and humidity represent another concern when it comes to viral transmission. As Wenger pointed out, “at lower temperatures, the virus survives for longer. There is a sweet spot between about 40 per cent and 60 per cent relative humidity in which the virus has a reduced lifetime.” Clearly, we need to take indoor air quality in schools very seriously for the sake of the health of students and teachers, and this is ever so true in the context of the current pandemic. As Jimenez urges, “we need to remove the virus from shared air in places where we have to continue sharing air. Otherwise, the economic damage and the human toll are going to be enormous.”

While in the immediate short term we may be forced to rely on opening of windows — preferably with CO2 sensors — as a means of mitigating airborne Covid transmission risk, this approach is very limited for a number of reasons. Classrooms may be single aspect, and thus with little or no scope for cross ventilation. They may also have as little as one opening window, perhaps just a high level window that can be difficult to open, meaning very limited ventilation, in particular on still days. And noise disruption may be a real problem when windows are open, particularly for street-facing classrooms in urban schools, or indeed all schools where break times are staggered, in the case of classrooms facing the school yard). Open windows may let rain in too, and the classrooms may become too cold when windows are open. And they may require close management by the teacher, to open windows if CO2 levels get too high, and to empty the classroom if CO2 levels still aren’t falling low enough. Even if the teacher is operating the windows perfectly it may not cause CO2 levels to fall sufficiently, depending on weather, the number and position of window openings, and the shape of the room. For all of these reasons, and the fact that Covid isn’t the only virus or pollutant we’ll be facing, I think we need to plan to implement strategies which deliver consistently good indoor air quality levels as seamlessly as possible. That means not freezing teachers and pupils, minimising noise disruption, and reducing the burden on teachers to manage ventilation levels via opening windows, in so far as can be reasonably expected. And I think that ultimately leads designers in the direction of passive house and Enerphit (the passive house retrofit standard), because of the combination of heat recovery ventilation — which introduces fresh and pre-warmed air — and a well-insulated, airtight fabric. These standards deliver thermal comfort while constantly supplying fresh air. Jeff Colley

ph+ | schools insight | 73



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74 | | issue 36




Where basements are present in low energy buildings, they can prove a weak spot without particular care and attention, as Passive House Association of Ireland board member John Morehead of Wain Morehead Architects Ltd explains.


ur temperate climate in Ireland can let us off lightly in achieving passive house levels of performance with above ground dwellings. However, once we build below ground, our advantages are lost due to the condensation risk caused by humid exterior conditions. Whether commercial or domestic, achieving NZEB with basements in Ireland challenges the design team with a series of sometimes conflicting demands that must all be fully addressed. With basements, thermal excellence is the new kid on the block that structural, moisture, radon and ventilation demands need to befriend. Basements in North America and Northern Europe are commonplace and evolved from simple foundation systems to the provision of storage and conditioned space. Insulation of basements took hold in the 1980s as 25 per cent of building energy losses were understood to be through these areas. Although exterior insulation clearly had both technical merit and reduced risks, the cheaper more convenient approach of using interior insulation became common and was associated with many failures.

Heat and moisture in basements Heat transfer in basements is generally outwards, vapour transport generally inwards, except in summer. Only when moisture transfer within basements is understood, should the appropriate thermal solutions be considered. Moisture from ground is in the form of liquid (saturated) and vapour. It can enter via breaches and through capillary action. Vapour is also introduced into the construction by air leakage and by vapour diffusion (higher to lower pressure) through the fabric itself. C35/45 concrete at construction stage holds 116 kg/m3 of moisture1. Low water content mixes are preferable. Concrete can absorb and retain significant moisture, but the incorrect placement of vapour tight materials can upset the balance. Once insulation is placed on the warm side of a concrete retaining wall, the risk of condensa-


tion increases as the concrete surface temperature lowers. Moisture permeable internal insulation and finishes permit the natural drying of the concrete retaining wall to the interior once mould-inhibiting materials are employed. The use of internal thermal solutions in basement construction requires a much higher standard of vapour control to be practical, whereas externally insulated basements, with the correct barrier protection placement and drainage strategies, make sense. Some mineral board solutions applied to the interior are particularly useful in tandem with other moisture and vapour control techniques in the transitional areas such as where basement walls break ground to meet the upper walls. Below this level systems with better vapour permeability and control should be the first choice. Guidance and achieving NZEB The lack of contemporary guidance available to the Irish practitioner on basements is worrying. Indeed, our academics should be encouraged to study issues of moisture and thermal management as a matter of urgency. Our own research in the area has been supported by empirical measurement on site, supported by hygrothermal analysis using Wufi Pro, with site-specific climate data. The standard BS-8102:2009 (Code of practice for protection of below ground structures against water from the ground) offers guidance on preventing the entry of water from surrounding ground into a structure below ground level but fails to address vapour transport mechanisms or condensation in any depth. It is civil engineering focused and discusses external moisture ingress potential, drainage and mitigation strategies. This iteration identifies three classes of external moisture protection of which types A (barrier) and C (drained) or a combination may be considered applicable for NZEB projects, but alternative syphon drainage systems need to be considered so as not to compromise air permeability requirements. The standard advises early engagement of a well-informed multidisciplinary team

Wufi Pro 6.5 Material data Oct 2017 – Typical Initial Moisture content

including tanking specialists in the design process. The document advocates contingency planning and acknowledges that defects may occur. It promotes the concept that feasible remedial measures be integrated. Although not limited to Parts A, C, F and L of the building regulations, these are the primary focus. Radon protection must not be overlooked. Thermal performance Once the building form has been determined, try a quick DEAP 4.2 (Dwelling Energy Assessment Procedure) spreadsheet assessment to see how the building complies with Part L and in particular to the MPEPC (maximum permitted energy performance coefficient) and MPCPC (maximum permitted carbon performance coefficient). In parallel, to assess the design performance of the building, assess the performance in the Passive House Planning Package (PHPP). Identify what you believe to be the performance targets for the external envelope and components. U-values for basements are calculated following BR 443 conventions for U-Values 2006 for Part L, and the methodology set out in ISO EN 13370:2017 section seven. Basement calculation methodologies use different boundary conditions, surface resistances and temperatures to those for typical ground floors or walls. The calculations addressing walls and floors are intertwined. As with calculations for rainscreen systems, simplistic calculation methods can be significantly inaccurate. An initial calculation to ISO EN 6946 is initially carried out to assess the floor (Uf) and wall (Uw) simplified losses. Once the ground equivalent thickness and average depth below ground for the entire basement is assessed, the additional influences of losses through the ground are then calculated in ISO EN13370. It is critical that the correct category of ground type and thermal conductivity from Table 7 of this standard is considered in any calculations. A real-world example from a semi basement gives some indication of the variance encountered.

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Ecocel Ecocel, due to its natural fibres creates a healthy indoor air quality and is Carbon Negative when installed.


U-Value ISO EN 6946

U-Value ISO EN 13370







Area Weighted Average



Table 1 Impact of conventions on U-value for 135m2 basement with 1.3 m average basement depth

In this case the wall U-value of 0.18 W/m2K is increased during the calculation and will require improved performance in the upper floor (above ground) walls to meet the area weighted average for the wall performance for the project. In an existing basement, where the average basement wall height is above 1.2 m, the basement walls and floors are both entered in the floor section of DEAP as separate entries. In an existing basement, where the average basement wall height is below 1.2 m, the basement walls are entered in the walls section of DEAP and the floors in the floor section of DEAP. This can cause significant difficulties where under floor heating Uf requirements need to be met. In a new basement, the basement walls and floors are entered as an area weighted average value in the floor section of DEAP as per Table 1 above.   Conclusion With basements it is critical to get your design team involved, together with a damp proofing specialist, early in the process to develop a coherent strategy suitable for the indoor and external environmental conditions and performance requirements. Front load your passive house and Part L compliance assessments early on in the design so as to ensure compliance can be achieved. A continual external insulation strategy is my first choice, but, if you must consider hybrid or internal insulation strategies, it is imperative that the appropriate hygrothermal analysis informs your solution. Specifications need to take account of the potential moisture levels the fabric will need to tolerate during the build, during drying out and beyond. Although simulation tools such as Wufi might inform the level of risk, a commonsense approach must always prevail, and you will find post occupancy monitoring an invaluable assurance that you have made the right choice.

above Graphs generated by Wain Morehead Associates using the WufiPro dynamic hygrothermal simulation tool calculate the potential consequences in terms of relative humidity and water content at the internal face of a reinforced concrete basement wall, using different approaches to insulation. Relatively humidity and water content both end up significantly lower with the external XPS (green) than the internal closed cell (purple) or internal mineral (blue) insulations.

Figure 1 Table 1 TGD L Domestic 2019

Table 1: Maximum Elemental U-value (W/m2K)1,2 Column 1: Fabric elements

Column 2: Area Weighted Average Elemental U-value

Column 3: Average Elemental U-value - individual element or section of element

Pitched roof insulation at ceiling Pitched roof insulation on slope Flat roof

0.16 0.16 0.20





Ground floor3



Other exposed floors



External doors, windows & rooflights



NOTES: 1. T he U-value includes the effect of unheated voids or other spaces. 2. F or alternative method of showing compliance see paragraph 3. For insulation of ground floors and exposed floors incorporating underfloor heating, see paragraph 4. W indows, doors and rooflights should have a maximum U-value of 1.4 W/m2K. 5. The NSAI Window Energy Performance Scheme (WEPS) provides a rating for windows combining heat loss and solar transmittance. The solar transmittance value g perp measures the solar energy through the window.

This article was published with the support of the Passive House Association of Ireland, a membership-based non profit organisation established to educate and inform people about evidence-based approaches to low energy building as characterised by the passive house standard. For more information visit

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PA S S I V E H O U S E +



entilation specialist Aereco has launched a new extract grill with integrated control indicator to meet building regulations that came into force during November 2020. The BXC hps provides the homeowner with information on the correct operating performance of the ventilation system and alerts the homeowner if there is a fault. According to the latest version of Technical Guidance Document F, all mechanical ventilation systems, “should indicate to the occupant that the system is operating correctly and if a fault has occurred”. TGD F also states that indicators “should be in a visible location to the occupant and not in a remote location such as in the attic or above the ceiling”. The new Aereco BXC hps is designed specifically to work with Aereco systems and provides assurance of compliance with the new regulations. A light indicating that the unit has power may not be sufficient to meet this requirement. “While the regulations are not very specific, I think it is reasonable to assume that the intention is that the indicator should fulfil a useful role in indicating to the occupant that there is more than just power to a fan, that the system is in some way fulfilling its intended role,” said Simon Jones, Aereco’s commercial director for the UK and Ireland. “Our goal in Aereco was to produce something that was indicative of the system performance. And I think we have done that through the BXC hps. It measures a threshold of performance in the system and indicates through visual and audible means if the system has fallen below it, or if there is a fault. “It also meets another requirement of the regulations in that it is in a visible location. As an integral part of an existing extract grill normally located in the kitchen or utility room, it is always in view. An app on a phone in someone’s pocket is unlikely to meet that requirement.” • (above) The new Aereco BXC hps extract grill with control indicator.

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Amvic Ireland launches passivestandard ICF system


mvic Ireland, long-known for its dual-insulated concrete formwork (ICF), has announced the launch of its new ultra-energy efficient wall system for passive-standard buildings. “The building regs require you to achieve the NZEB standard and we’ve been achieving that without any difficulty for the last three years, using our existing Amvic 300 system,” said Pat Martin, director of Amvic Ireland. Now the company has gone one further: Amvic 350 Passive is an ICF system aimed squarely at passive house development, delivering a wall U-value of 0.15. “We’ve been operating for the last fifteen years, supplying both self-builder and developers with our ICF system. Our current product, Amvic 300, has 75 mm of insulation on the outside, a 150 mm concrete core and 75 more mm of insulation on the inside.” Amvic’s systems bring top class energy efficiency benefits due to their use of expanded polystyrene (EPS) insulation, both internally and externally. “We’ve just launched a new product that takes the insulation to the next level. We call it Amvic 350 Passive, comprising 100 mm of insulation either side of the 150 mm concrete core, all in high-density enhanced EPS,” Pat Martin said. Apart from the energy performance, he said that on-site work is aided greatly by reducing the need for wet trades, among other benefits. “It forms the basis for a passive building. Any chosen finish can be applied, such as render, or brick or stone cladding, timber or metal – whatever is called for by the architect.” He said that the system beats light frame systems due to its flexibility and the lack of long lead times. “Our ICF is very simple to build and available ex-stock, meaning there is no waiting around for design and manufacture, plus it has all of the other benefits of Amvic ICF including fire resistance, structural strength, acoustic performance, and rapid build and simplicity.” •

(below) The new Amvic 350 Passive ICF system delivers U-values of 0.15.

PA S S I V E H O U S E +


Cellulose insulation Mannok announces can boost airtightness new product names — Ecocel after rebrand



e all know the value of good insulation in improving the energy performance of a building, so why then are attics often an afterthought? John Egan of Cork-based cellulose insulation manufacturer Ecocel says that despite increased awareness of the need for good U-values, the full potential of attic insulation to insulate a property is often not realised. “Insulating the attic is the simplest, most efficient thing you can do in the house, but it just gets ignored,” he said. The figures are impressive: 300 mm of Ecocel’s cellulose insulation, weighing-in at between 30 and 35 kilograms per square metre, provides a U-value of 0.11 W/m²K. “If every attic was insulted to that level, we’d be saving a lot of heat,” Egan said. There is more to it than that, though, Egan says. In fact, cellulose insulation improves airtightness, something he puts down to its inherent nature. “First you get a U-value of 0.11 but you’re getting [additional] airtightness. Literally just putting cellulose in the attic improves the airtightness by 20 per cent. We’ve undertaken two preliminary tests and have just received word from Enterprise Ireland they will fund three independent tests through third-level institutes to verify this,” he said. “It’s a lot to do with the density of the material, and also that it’s blown-in so it goes everywhere. Cellulose naturally seals around pipes and electrics,” he said. As a recycled material, cellulose also has the advantage of low embodied energy, something that has been recognised this year: Ecocel’s Scottish distributor, Ecocel Scotland, has been awarded Most Sustainable Home Insulation Provider in the 2020 Scottish Enterprise Awards. “Low embodied energy is very important to us,” Egan added. “We produce just 0.3 kilos of carbon per kilo of insulation material.” • (above) Cellulose insulation can not only boost attic U-values but also airtightness, according to the company.

he rebrand from Quinn to Mannok was announced in September, with the official name change completed on 16 November, marking a major milestone for the company on a rebrand journey which will take up to 12 months to fully complete. In a year that has given us so much uncertainty and unprecedented challenges, it is a bold move for any company to take on a rebrand. Mannok said the timing of the launch tells us a lot about the company’s intentions – they’re here for the long term. A key message coming immediately from Mannok is a firm commitment to continue growing their export market, a message which is reaffirmed by their more recent announcement of a new exclusivity deal with one of the UK’s largest merchant buying groups, NBG (National Buying Group) for their Master Grade Cement. On the home front, new Mannok branded lorries are already on the road, replacing the familiar sight of Quinn green trucks, and the company said there will be more visual changes in the coming weeks, including new product packaging which will be in production early in 2021. Meanwhile Mannok’s newly designed cement bags carry the bold new brand colours with the distinctive Mannok M, ensuring they will be easily recognisable. As the company’s biggest selling bagged cement product, Master Grade Cement will be packaged in the Mannok teal, the primary brand colour, replacing the familiar blue bag. Meanwhile Premium Grade Cement will be packaged in the vibrant Mannok green. Customers and specifiers should also take note of some product name changes and the integration of the company’s old sub-brands into one single brand identity, Mannok. So, there will no longer be separate brand names to replace Quinn Therm, Quinn Lite, Quinn Cement, Quinn Precast, Quinn Rooftiles and Quinn Lite Pac. Going forward, all products will simply be branded Mannok. The company will of course continue with the same product lines, which are listed in the accompanying table. •

AIRCRETE THERMAL BLOCKS RANGE Before rebrand Quinn Lite High Strength Ten Quinn Lite Seven Blocks Quinn Lite Standard Blocks Quinn Lite Super Blocks Quinn Lite Coursing Units Quinn Lite Foundation Blocks

After rebrand Mannok Aircrete High Ten Mannok Aircrete Seven Mannok Aircrete Standard Mannok Aircrete Super Mannok Aircrete Coursing units Mannok Aircrete Foundation

EPS INSULATION RANGE Before rebrand Quinn Lite Pac EPS 70 Quinn Lite Pac EPS 100 Quinn Lite Pac EPS 150 Quinn Lite Pac EPS 200 Quinn Lite Pac EPS EPS Pearl 70 Quinn Lite Pack EPS Pearl 100 Quinn Lite Pac Dorm

After rebrand EPS 70 EPS 100 EPS 150 EPS 200 EPS Pearl 70 EPS Pearl 100 EPS Dorm

PIR INSULATION RANGE Before rebrand Quinn Therm QF Quinn Therm QW Quinn Therm QW Cavity Wall Quinn Therm Isoshield Full Fill Quinn Therm QW-STFI Steel/Timber Frame Insulation Quinn Therm QL Foil Quinn Therm QL-Kraft Quinn Therm QR Quinn Therm EASI-DORM Quinn Therm QRFR-FFR Quinn Therm QRFR-GFR Quinn Therm QRFR-DPFR Quinn Therm QRFR-PLY

After rebrand Mannok Therm Floor / MF Mannok Therm Wall / MW Mannok Therm Cavity / MC Mannok IsoShield Mannok IsoFrame Mannok Therm Laminate-Foil / MLF Mannok Therm Laminate-Kraft / MLK Mannok Therm Roof / MR Mannok Therm EASI-DORM Mannok Therm Roof / MFR-FFR Mannok Therm Roof / MFR-GFR Mannok Therm Roof / MFR-DPFR Mannok Therm Roof / MFR-PLY

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PA S S I V E H O U S E +

Passive Building Structures aims to cut carbon both on & off site The fabric-first insulated concrete formwork system and insulated foundation from Passive Building Structures.


uilding envelope specialist Passive Building Structures is aiming to substantially cut the carbon footprint of its projects in 2021 both by increasing the thermal performance of its builds and cutting their embodied energy. “We plan to work in a more sustainable and socially responsible way by improving the performance of our buildings and by reducing their embodied carbon too,” the company’s Pearce McKenna told Passive House Plus. Passive Building Structures specialises in fabric-first, insulated concrete formwork construction with integrated floor and roof elements.

“Our craft is centred around a fabricfirst approach to building, along with high functioning materials which work cohesively to deliver lower heating and cooling demand,” McKenna said. “Our sectional details ensure we eliminate any thermal bridging. Our insulated concrete formwork system ensures both inherent insulation and airtightness.” The company has recently updated its ICF packages to offer U-values as low as 0.11, but all of its systems have a U-value of 0.15 or under. “All of our offerings also come with the benefit of details for minimal thermal bridging and airtightness as standard,” McKenna said.

“We believe that there is not enough focus placed on the building fabric and how it can reduce energy consumption. Our building fabric needs zero maintenance and lasts the entirety of the building’s lifecycle.” Besides operational energy, the company is making wider efforts to reduce its environmental impact. “We intend to use over 45 per cent GGBS in our concrete mix as standard to further reduce the embodied carbon of our builds. We have already used a 45 per cent GGBS mix on our latest passive house project in Manchester (featured in issue 35 of Passive House Plus)”. “We also minimise waste on site, any EPS leftover is reused and EPS that cannot be reused is recycled.” Passive Building Structures has also started to offset the business travel footprint of its employees. “We know this isn’t a long-term sustainable solution, but we think in the shorter term it is a positive step to take. We are also pledging to plant trees for every build we have from the start of 2021 with the goal of reaching 10,000 trees planted by the end of 2021.” “We are continuing to look at ways we can improve our processes. We believe that the building sector has a huge role to play in mitigating and addressing climate change. As we look towards the future of low energy housing, the long terms goals of financial, social and environmental sustainability are clear — however we must first look at our short-term efforts to ensure that our builds perform as intended.” •

Engage ventilation validators at design stage — Evolved Energy Solutions


ZEB consultancy Evolved Energy Solutions is now offering ventilation validation services for domestic building projects after company director Brian Sweeney was added to the NSAI list of registered ventilation validators. Sweeney said the firm had already started validating systems under the new regulations and had encountered some issues with incorrect sizing of natural ventilation, and flow rate issues in mechanical systems. “We would encourage clients to engage us early for a design review and trial testing,” he said. “We are also keen to have early contact with those commissioning systems, as any difference in flow rate between commissioning and validation of more than one litre per second could cause a problem with sign off. The earlier we are engaged the less likely there are to be issues on the day of the test.” The company, which is co-owned by Sweeney and his business

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partner Niamh O’Sullivan, is focused on independent energy and acoustic testing, including BER assessment, airtightness testing, Part L compliance, acoustic testing and thermal imaging. “Ventilation validation must come from an independent validator and we feel we are best placed to provide that service. We don’t design or sell ventilation systems, we just validate them, which means our service is completely independent.” Under a clause in the latest version of Technical Guidance Document F, which came into force in November 2020, ventilation systems must be validated by independent and certified third parties to ensure they meet intended flow rates. Evolved Energy Solutions now employs seven full time staff, and expects three more of its employees to be added to the NSAI list early next year after undertaking training at WWETB. See

PA S S I V E H O U S E +

Unipipe launch easy underfloor heating for upper floors


nipipe has announced the launch to the Irish market of underfloor heating and cooling systems from German manufacturer MFH Systems. MFH’s innovative underfloor heating product is designed to be installed without the use of wet screed. The underfloor heating pipework is fitted into shallow pre-engineered EPS boards, with an aluminium coating that helps to transfer heat optimally into the floor finish above. “These underfloor heating systems are ideal for new build or retrofit. They offer fast response and are effective at low heating temperatures,” Unipipe managing director Paul O’Donnell told Passive House Plus. “At just 20 mm high the system is ideal for use upstairs in timber floors and in homes with engineered joists.” He added: “We also supply a 5 mm strong board, made from recycled materials, which when placed over the MFH 20 mm boards can then take ceramic tiles. This solution is ideal for apartments and also offers the added benefit of sound-proofing the floors.” O’Donnell said that MFH’s underfloor heating systems would challenge perceptions about how easy it is to install underfloor heating in the first floor and above. “We are offering MFH Systems in response to the many homes where people tell us they have to settle for ugly radiators, as it’s perceived to be too awkward to use underfloor heating.” Versions of the MFH Systems underfloor heating product are also available for installation in walls and ceilings. • (above) Underfloor heating from MFH Systems is designed to be installed without wet screed.


Kilcarrig launches new lower carbon dry mix silo mortar


ilcarrig Quarries has introduced a new low carbon dry mix mortar to the market that uses ground granulated blast furnace slag (GGBS) to replace up to 35% of its cementitious binder. Thomas McDonald, director of Kilcarrig Quarries (also trading as Milford Quarries), says the main advantage of this new mortar is that it cures at a similar rate to traditional mortar, something that was previously not the case for mortar with a high GGBS content. “We were using about 20 per cent GGBS, but now we’re able to use nearly twice as much, so it’s up to 35 per cent of our total cementitious binder,” he said. GGBS is sometimes used in mortar in small doses but setting times can be slower, something exacerbated by the changeable Irish weather. Kilcarrig’s new eco-mortar is intended to change this. The secret is a new activator, developed by Ecocem Ireland Limited. “We wanted to use more GGBS to enhance the sustainability of our mortar but were concerned that this could have a detrimental impact on the early age strength development,” McDonald said. “We were already speaking to Ecocem about their AccelR8 activator for blocks and they were able to supply a new product called EcoFormulaT. This has been specifically designed to boost the early age strength of GGBS based dry mortar products.” Andy Christian, sales manager at Ecocem Ireland, which first introduced GGBS cement products to Ireland in 2003, says that the product was driven by developer demand.

“Durkan Residential were looking for low-carbon products for their sustainable developments and have a strong history of using GGBS. Traditionally, people were not putting GGBS into dry mortar, but this product shows that it can be done without sacrificing any of the key performance targets. “Kilcarrig were interested right from the start because they wanted something that could differentiate them from other products on the market.” Kilcarrig’s new eco-mortar reduces the embodied carbon of mortar by around 25 per cent compared to traditional mortar mixes, as well as offering all of the benefits you would expect from a factory-mixed product. The consistency, optimum open time and early age strength development make it an ideal choice for housing developers. The new product is now being used at Durkan’s scheme of 47 passive houses at Church Road in Killiney, which are being constructed from single-leaf blockwork with external insulation, a system Durkan has pioneered on residential passive house schemes. Barry Durkan of Durkan Residential said: “We are delighted with the performance of the eco-mortar in terms of both strength and workability on site.” •

(above) Kilcarrig Quarries, also trading as Milford Quarries (inset), has launched a new dry mix silo mortar with a higher quantity of GGBS, thanks to a new activator from Ecocem. The new mortar is being used on a scheme of 47 passive houses in Killiney by Durkan Residential.

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PA S S I V E H O U S E +

New heat pumps and pellet stoves from Waterford Stanley W

aterford Stanley has announced it latest line-up of renewable heating products, comprising air-to-water heat pumps, and room and central heating pellet stoves designed to meet Ecodesign 2022, the new European standard for lowering emissions from wood burning and multi-fuel stoves. Robert Moore, head of sales at Waterford Stanley said: “It’s an exciting and challenging time. Our product portfolio has undergone tremendous change with a significant move to renewable energy solutions including electric, pellet and heat pumps.” Waterford Stanley offers two variable output heat pump options, the HP7 (7 kW) and the HP12 (12 kW). Both models are inverter controlled, allowing the heat pump output to match the heat requirement of the house. The heat pumps also have intelligent software that will adapt to the heat requirement of the house over the first three days of use. The heat pumps come with either a 50-litre buffer tank including a circulation pump for homes with an existing cylinder, or a 200-litre glass-lined cylinder together with a 50-litre buffer tank and circulation pump and heater, all in a single unit. “Any unit within the A++ rated Stanley range can deliver up to five times the amount of energy for every 1 kW of electricity,” the company said. Smart remote access to your heating system lets users control settings and temperature. All models feature a web module which enables full remote diagnostic access, and indepen-

dent data logging of electrical energy is used in the provision of central heating and domestic hot water. Full Stanley technical advisory services are also available. Meanwhile Waterford Stanley’s pellet burning stoves offer up to 96 per cent efficiency and are electronically controlled through a remote control or in-built programmer. There are five room heating models available in different colour finishes, providing between 3 kW and 9 kW heat output to the room; all are balanced flued. The company’s central heating pellet stoves heat from eight to sixteen radiators depending on the model, and all three models have large internal hoppers and self-cleaning burners, meaning less refuelling and reduced waste. They are fully adjustable in terms of time and temperature including sleep timer and programmable controller with up to six on/off times per day. Waterford Stanley has also announced the appointment of Donal Reilly to the position of heat pump business development manager, covering the whole island of Ireland. He has a background in both heating, plumping and renewable energy technologies. Donal is a fully qualified civil engineer and is also FETAC qualified in the following areas: BER assessing, air source heat pumps, solar thermal and biomass. He has also spent two years teaching HETAC accredited renewable energy courses in GMIT Galway. For more information see •

(above) The WSL 142 indoor unit, part of the 12 kW HP12 air-to-water heat pump system launched by Waterford Stanley. offering ventilation validation


eading energy assessment experts are now offering ventilation validation services under Part F of the building regulations after two of the company’s employees were added to the NSAI list of registered ventilation validators. Daniel Fennell and David Coyle of were added to the list in October 2020 after completing relevant training at the Waterford Wexford Education & Training Board. Both have educational backgrounds in energy engineering. Fennell has experience in domestic and

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commercial BER assessment and airtightness testing, while specialising in technical assessments for heat pump grants. Coyle currently works principally on Part L compliance for new build developments. provides a range of independent energy and acoustic consultancy and testing services. Fennell told Passive House Plus that the company works on residential developments from design stage, undertaking Part L and F compliance, airtightness and acoustic testing and BER assessment, and that ventilation validation will compliment this existing range of services.

“We see ventilation as really important,” he said. “It is something that has really been overlooked in housing so far.” Fennell said that the company strongly encourages the use of mechanical ventilation in new build housing, particularly as natural ventilation is not advised on dwellings achieving airtightness of better than 3 m3/m2/yr. He welcomed the introduction of ventilation validation as an important tool in ensuring that ventilation systems perform as designed and deliver good indoor air quality for building occupants. For more see •

PA S S I V E H O U S E +

NOVUS Windows announce partnership with Idealcombi


Tegral slates adopt new brand name Cedral


OVUS Windows have announced a new partnership with Idealcombi A/S, the largest window manufacturer in Denmark with over 100,000 square metres of production facilities. NOVUS Windows managing director Micheál Dunne told Passive House Plus that this partnership is “already proving to be quite successful with an unprecedented response from the Irish market”. “The co-operation and technical support provided by Idealcombi A/S is proving to be a key tool in meeting market demand for ever improving thermal performance,” he said. “Our customers appreciate the benefits of the technological advancements they are seeing with the new idealcore technology, and the aesthetic provided by the frameless Futura+ and the Frame and Nation IC window and door ranges. The quality of the product speaks for itself.” NOVUS Windows was founded in 2016 by Micheál Dunne and Paul Duffy, both of whom have extensive backgrounds supplying Danish timber and aluwood windows to the Irish market. Dunne continued: “Our mission is to provide innovative design solutions to our customers, not only from an aesthetic point of view but also to ensure the most suitable energy solution, optimising orientation, glazing specifications and facade technologies. This coupled with our master tradesmen on-site ensure that our customers receive a finished product that is unrivalled within the Irish market. “All Idealcombi products incorporate the revolutionary idealcore technology. This innovative technology is a quantum leap forward in the design and performance of aluwood windows and doors. Not only does it significantly improve the thermal performance but it completely eradicates the design flaws that have long been associated with aluclad windows. Interstitial condensation, timber degradation and rot are now a thing of the past with our windows, as the idealcore provides an imperishable material within the wet zone.” Dunne said this guarantees an extended design life of 70 years when maintained correctly. The idealcore thermal PUR offers a lambda (thermal conductivity) value of just 0.074, compared to typical values of 0.13 for pine wood and 0.25 for composite PVC. NOVUS Windows operates nationwide offering a consultative sales service and providing advice on all aspects of window and door design. “We offer the slimmest frames available on the market for fixed, openable, terrace doors, sliding doors and tilt and turn units, all with a unitised 53 mm section,” Dunne added. For more see •


egral, the Irish manufacturer of fibre cement roof slates, will now fall under the new Etex Ireland brand, while its classic roof slates will be marketed under the brand name Cedral. In 1988 Tegral — with its factory in Athy, Co Kildare — joined the global building materials group Etex. “With a passion for perfection, a dedication to customer experience and a commitment to sustainability, as a global group, Etex has looked closely at how they can facilitate improvements in all of these areas for their customers,” a statement from Etex Ireland announcing the rebrand read. Tegral is most known across Ireland for the roofing sector of its business. As part of the rebrand, Tegral slates are now Cedral slates, Etex’s global brand name for domestic roofing and façade products. The company’s new brands are Cedral (for home façade and roofing products), Euronit (for agricultural buildings), Equitone (for architectural façades) and Viriform (for commercial and structural engineering). Paddy Kelly, managing director of Tegral / Etex Ireland, said: “This is an incredibly exciting time for us, and we look forward to seeing the new brands out there in the market. We have been part of Etex for a long time now and this rebrand is one that now unites us to face global challenges together, like housing shortages, sustainability and more. Our commitment to continual innovation and ever improving standards remains unwavering. We are the same people you know and trust, still manufactured in Athy, still guaranteed Irish, just with a new name.” • (above) Tegral’s roof slates will be marketed under the new brand name Cedral.

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Pro clima launch spray applicator for airtight paints


ro clima have launched Aerofixx, an innovative handheld spray applicator for the Aerosana Visconn range of airtightness liquid paints. The spray applicator simplifies the intricate airtightness details often seen in retrofit or new build. Aerofixx is designed to greatly simplify airtightness details and present installers with a unique solution to address often complex and time-consuming airtightness details. It allows for the quick and easy application of Aerosana Visconn and Aerosana Visconn Fibre onto both rough and smooth substrates such as timber, concrete blocks, wood fibre boards, OSB, stone and plaster. Its small, portable design allows for it to be operated using only one hand and is ideal for creating an airtight seal in hard-toreach areas. Aerosana Visconn and Aerosana Visconn Fibre come in ready-to-use 600 ml foil cartridges and the rate of spray can be easily adjusted to suit the installer’s needs. Pro clima have also launched Solitex Fronta Quattro FB Connect, a flame-retardant (B-s1, d0), UV resistant, wind-tight breather

membrane for open jointed cladding up to 30 mm, incorporating an integrated wind-tightness tape for sealing laps. The membrane does not include any printed branding, making it ideal for installation behind open jointed cladding. The integrated ‘connect’ tape ensures quick and reliable adhesion at all horizontal laps maximising wind-tightness and weather protection. Given the increased awareness in relation to the fire resistance of building materials. Solitex Fronta Quattro FB offers increased safety while also permitting the building envelope to breathe. Both new pro clima products are available from Ecological Building Systems.

house as a sample case study including in-depth details for airtightness, wind tightness and thermal continuity. The book is ideal for passive house enthusiasts and can be purchased from Crosson has also recorded a series of video blog posts outlining the philosophy and products used in his own passive build. You can watch them at www. passive-house-insulation-series. •

‘Understanding Passivhaus’ Meanwhile, Ecological Building Systems has contributed to the second edition of the book Understanding Passivhaus by Emma Walshaw. Among the many outstanding case studies and in-depth details included within the publication, Ecological’s group technical manager, Niall Crosson, provided his own passive

NuWave Sensors launches CO2 monitor for schools N

uWave Sensors, developers of smart air quality sensors designed to continuously monitor airborne contaminants in industrial and commercial environments, has unveiled a new carbon dioxide sensor that allows schools to help prevent the spread of Covid-19, while also avoiding energy waste. NuWave’s CaDi CO2 sensor is a sister unit to its cair Air Quality Monitor, sold under the cair brand. “The world has come to think about hand hygiene, but at NuWave we’ve always been aware of air hygiene,” said NuWave’s co-founder Lisa Ainsworth. “We produce a range of air hygiene sensors, monitoring basic things like temperature and humidity and more advanced properties like particulate matter and CO2, all the way through to air safety, where we look for pathogens in the air,” she said. NuWave’s goal with CaDi CO2 is to provide schools with an effective means of monitoring carbon dioxide levels in the air, displaying real-time results on a simple to understand LED display. CaDi also has an open API that can be linked into ventilation systems or display information via an app. Professor Stephen Daniels, NuWave’s chief technology officer and other co-founder, says ventilation now matters more than ever. “If you have poor ventilation in an occupied space then you have an environment where all sorts of things can spread more easily. Poor ventilation can also contribute to mould growth which in turn can lead to the development of respiratory problems. It is important to keep a well-ventilated environment.” Monitoring levels of CO2 can inform schools about how well classrooms are ventilated, which in turn can help to prevent the spread of Covid-19, by encouraging staff to open windows or turn on ventilation systems when needed. “CO2 is a good proxy for ventilation,” Daniels said.

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Daniels added that good ventilation is something that should not be left to chance. “We come at it from an anti-contamination perspective, not just a gadget. Buildings have become so airtight that if the filters aren’t changed or the mechanical ventilation isn’t right you have a problem.” For Ainsworth, monitoring carbon dioxide in the air will mean that schools have a real-time view of ventilation, rather than having to leave windows open constantly while running heating at a higher temperature. “We could end up spending far too much on overheating classrooms, instead of just opening the windows when you need to,” she said. •

(above) The new CaDi CO2 sensor is designed to monitor ventilation levels in school environments.

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tratherm is now offer Foamglas cellular glass insulation from Owens Corning to achieve passive thermal bridge detailing for Irish construction. Foamglas is a lightweight, rigid, and durable material composed of completely sealed glass cells. Foamglas is non-combustible, provides superior compressive strength, moisture resistance and dimensional stability, and offers long lasting thermal performance. A wide range of shapes and sizes are available for building, equipment and industrial specifications. Xtratherm have developed details using Foamglas to meet the higher performances required to achieve NZEB. Mark Magennis of Xtratherm said: “Achieving passive Psi-values in many instances can only be achieved by completely bridging the construction with a material that is both

thermal and structural. Foamglas is that product. “We analysed detailing under the NSAI thermal modellers scheme and found junctions such as party walls, eaves and parapet walls on flat roofs can benefit from such a thermal break.” Although regulations ask that all thermal bridging detailing be accounted for, often junctions such as thresholds and cavity trays are simply ignored. Magennis continued: “Openings at doors and windows constitute a significant heat loss junction, particularly when full glazed wall and patio doors are specified. Xtratherm’s detailing using Foamglas offers a complete solution both thermally and from the threat of moisture damage.” Where a non-combustible insulation is required, Foamglas with its A1 Euroclass

fire classification is ideal. Foamglas insulation at ground level also provides the added assurance of full resistance to moisture and radon. For more contact the Xtratherm technical team, see www. for details. •

(above) Xtratherm now supply Foamglas structural thermal breaks.

Choose a heating system early in your build – Grant

The outdoor unit of Grant’s Aerona³ R32 10 kW air-to-water air source heat pump.


t is vital to start planning the heating system in the early stages of a new build project, according to leading Irish heating manufacturer Grant. This will help when considering room layout and can save time and money in the long run. Homeowners should also consider the current and future needs of the property and whether they would like to install underfloor heating or radiators in each room, as this can influence the decision of what heat source will drive the system. Given the importance of choosing the right heating system for a property, the technical specialists at Grant are providing self-builders with a bespoke home heating design, specification and supply solution to suit their needs and ensure building regulations are met. With a growing focus on sustainability and

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reducing environmental impact, incorporating renewable energy sources for home heating into a new build home is crucial to meet building regulations and future-proof the property. Grant’s diverse range of innovative heating technologies have been designed and manufactured in Ireland since 1977. Designed to work together, Grant’s highly efficient heating products offer homeowners a reliable full heating solution under one roof. A popular choice for new builds is the highly efficient Grant Aerona³ R32 air-towater air source heat pump which provides compliance and an energy efficient, sustainable and cost-effective way to heat a property. With an ErP rating of A+++, the Aerona³ R32 range is available in outputs of 6 kW, 10 kW, 13 kW and 17 kW, and the units can help to

achieve nearly zero energy building (NZEB) standards, as required for all new build properties in Ireland. Once the main heat source is chosen, a high performance, energy efficient hot water cylinder will be selected to support the system’s overall efficiency. Grant’s pre-plumbed hot water cylinder range is designed to heat water faster and more efficiently than standard cylinders and ensure hot water is available twenty-four seven. To heat individual rooms, underfloor heating and aluminium radiators are great modern heat emitter choices and can support the overall design and architecture of the space whilst also creating comfort. The Grant Uflex underfloor heating system works effectively with an air-to-water heat pump, helping to save energy and money as both systems work at low temperatures, so together use less energy. Aluminium radiators, such as the Grant Afinia range are highly efficient and compatible with high and low temperature systems. With excellent conductivity and vertical and horizontal combinations, the Afinia range also delivers flexibility with installations. Grant continues to operate at the forefront of the heating industry, consistently providing those who are working on new build projects with comfortable, sustainable and cost-effective ways to heat their homes. Visit www. for more information on Grant’s range of innovative heating solutions. You can also follow Grant on Facebook and Twitter @ GrantIRL or Instagram @Grant_IRL. •

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Prestige Aluclad supplying passive Viking windows nationwide P

(above) The Viking Passive Ultra Aluclad window, supplied in Ireland by the newly rebranded Prestige Aluclad.

restige Aluclad is the new brand name in Ireland for Viking Windows, the supplier of passive house and low energy timber and aluminium-clad windows from Estonian manufacturer Viking. “We still supply Viking Windows, but we are also widening our range to supply other products now too,” Declan Loy of Prestige Aluclad told Passive House Plus. Loy said that the new brand name was chosen to represent the company’s product range. “What Prestige Aluclad really stands for is quality. We’re the number one bespoke supplier of aluclad windows in Ireland, and by bespoke, I mean things like large, fixed panes of glass, front entrance doors and floor-to-ceiling opening sections.” Loy said that aluminium-clad timber offers strength and stability, as well as being an eco-friendlier option than PVC. “We’ve all been driven to improve operational energy use in the home but nobody’s looking at the embodied energy. Aluclad timber is a way of reducing embodied energy and carbon, it’s A-rated in the BRE green guide,” he said. Prestige Aluclad’s range includes two Passive House Institute certified windows, the Passive Timber and Passive Ultra Aluclad, both of which deliver whole-unit U-values as low as 0.63. Loy said that the design-conscious market is increasingly concerned with energy performance, and aluclad is ideal for this market as it not only offers exceptional aesthetics but delivers top class performance too. The company’s range also includes other triple glazed options as well as double glazing and inward-opening units. Prestige Aluclad also supplies lift-and-slide patio doors, bespoke entrance doors, glass-to-glass corner windows, and floor-to-ceiling windows with a low U-value of 0.74. The company’s products come with a ten-year warranty. Prestige Aluclad also boasts seven partner showrooms in Dundalk, Dublin, Nenagh, Belfast, Cork, Galway and Donegal, and offers lead times of just five to six weeks. For more see •

Want to see your ad in the next issue of the magazine? To enquire about advertising, contact Jeff Colley on +353 (0)1 210 7513 or email

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Firebird launches new quick plumb unit


Gyproc launches new single coat plaster

(above) The Firebird range of Enviroair heat pumps.


irebird has announced the launch of its new Envirocyl Quick Plumb Unit, which provides an easy solution when installing a Firebird Enviroair heat pump. The new unit was designed to allow for the combination of different heat sources in an efficient, space saving and cost-effective manner. With a large proportion of the plumbing work already done, a Firebird Quick Plumb Unit is designed to substantially cut onsite installation time, thereby reducing the amount of disruption to the customer. For installations using multiple cylinders, the unit helps to ensure consistency from one installation to the next. “For over 40 years Firebird has been a global market leader in manufacturing high performance solutions for the home heating market, with a customer base covering the island of Ireland, Great Britain, France, New Zealand, USA, Germany, Scandinavia and the Middle East,” a statement from the company read. It added that over the past number of years the company has had a clear focus on sustainability and has dedicated significant resources and investment to developing products that will future proof home heating. All Firebird products are developed with an emphasis on ease of installation. These products include the company’s patented Enviroair air source heat pumps, which are NZEB (nearly zero energy building) compliant, with a low running cost PCB controller and high-tech intelligent heating controls. Firebird said that a Quick Plumb Unit brings a consistency to each installation for a neater, more aesthetically appealing finish. It is a fully pre-plumbed and pre-wired indoor unit with wheels for easy movable access. The unit also has a built-in drip tray for a quick drain down safe system and a chain lockable door for child safety. “Having all of the products developed in-house means that knowledgeable and experienced technicians are always on hand to provide installation support as well as a trusted back up after sales support when needed.” For more information on Firebird’s Enviroair heat pump product range and the new Envirocyl Quick Plumb Unit, visit •


yproc has launched OneCoat plaster, a gypsum-based lightweight plaster that the company says is easier to spread and less physically demanding than other systems — leading to greater speed of use, reduced working time and improving performance on site. “Gyproc OneCoat also provides a high quality, durable finish with a single application, saving time and labour costs whilst improving the quality of indoor air by removing formaldehyde from the air,” a statement from the company read. When applied to masonry walls Gyproc OneCoat can provide a significant contribution to the overall airtightness performance strategy of a building, according to the company. Test results undertaken in an INAB accredited laboratory demonstrated that the application of 10 mm Gyproc OneCoat over 100 mm Irish manufactured concrete blocks, laid on edge, offered an air permeability performance of 0.028 m3/h.m2 (50pa). As an added benefit, Gyproc said its Activ’Air technology removes formaldehyde from indoor air, thus improving indoor air quality. When hand mixing Gyproc OneCoat, for optimum results, mixing should be carried out with an 1800-watt mechanical drill. For machine application, Gyproc OneCoat plaster works well with most electrical spraying machines. Gyproc OneCoat plaster is applied directly to blockwork and can be built out to a minimum depth of 10 mm, up to 15 mm in a single application. It can be built out to a depth of 13 mm for party walls to meet building regulations for acoustic performance. If required, Gyproc OneCoat can also be built out to a maximum depth of 25 mm (for more details please see product data sheet at “This new one coat plaster speeds up the plastering process – no need to wait for a sand and cement undercoat to dry/ set before applying a finish coat. Gyproc OneCoat is a single plaster application, and with a four to five hour setting time, you can have your walls finished in one day,” the company said. • (above) Gyproc’s new OneCoat plaster can be built out to a maximum depth of 25 mm.

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Do your walls behave like a Jaffa Cake? Toby Cambray writes on the many lessons that the inimitable biscuit cake can teach us about how building materials deal with moisture.


he topic of VAT on retrofit is (for our UK readership) a point of significant concern, the disparity making it disproportionately costly to refurbish than to build new, setting up undesirable incentives (to knock down and re-build, with all the additional up-front carbon) and arbitrarily and unfairly penalising one type of building work over another. If you have not done so already, I would urge you to sign the petition to correct this injustice, initiated by the inimitable Harry Paticas, and available at But there is another burning injustice in the realm of VAT of even greater interest to building physicists. Back in 1991, Her Majesty’s Revenue and Customs embarked on a campaign to impose VAT on McVitie’s Jaffa Cakes. Somewhat counterintuitively, cakes are considered a staple and not subject to VAT whereas biscuits are a luxury and are burdened with VAT. HMRC claim to have simply wanted the additional revenue, but

scope, now usually called a hygrometer. Hygroscopicity is the relationship between the moisture content of a material and the humidity of the environment surrounding it and within its pores. It tells us about the ability of a material to take up and release moisture to the air, and its ability to store or hold moisture. Hygroscopicity is not therefore a binary property; it’s not very accurate to say material ‘A’ is hygroscopic and material ‘B’ is not. Not even is it sufficient to express hygroscopicity as a single parameter in the way that we (to a first-order of accuracy) give say density and conductivity. Hygroscopicity is fully represented as a curve showing, for a particular material, the water content at equilibrium at a certain relative humidity. In the case of cakes, they are most enjoyable when somewhat moist; their moisture content at the optimal point of taste corresponds to a higher humidity than typical indoor air. If left exposed, the moisture in

single small biscuit in a tin with a large cake would not draw sufficient moisture out of the cake to render it entirely unpalatable, while the biscuit itself would degenerate into a limp shadow of its former self. This is because the amount of moisture a ginger nut takes up, even at elevated relative humidity, is in absolute terms small in comparison the moisture in a densely fruited, brandy-infused, bumper-sized Christmas cake for example. Conversely, a lonely and most petite fairy cake would not severely impact the shortness of a generous stash of Dean’s, despite succumbing to a brittle fate itself. It’s fascinating to explore the parallels between what we do in the construction industry and how others approach seemingly unrelated problems and phenomena in different walks of life. The world of food science has much more to teach us about buildings; I am looking forward to tucking into a veritable feast in subsequent columns. n

Conversely, biscuits are best enjoyed in a relatively dry state which creates the subtle crunch of the classic digestive. the campaign was pursued with such fervour I am convinced it was driven by a Jaffa-hating faction within the department. The case went to court, and arguments were advanced pertaining to the size of the snack, placement in relation to biscuits within shops, the presence of partial chocolate covering and the use (or not) of a fork to facilitate consumption. McVitie’s apparently went so far as to bake a giant version to illustrate the inherent cakeyness of the Jaffa. However, one indisputable fact helped to turn the case: when left out to go stale, biscuits go soft, but cakes go hard. Reading about this improbable case recently, it occurred to me that it is an elegant example of hygroscopicity as one could hope for – an important property in the field of moisture in buildings. Hygro (as distinct from hydro) pertains to humidity; the etymology suggests the ‘scopic’ portion of the word is vestigial, deriving from the instrument used to measure or look at the property. Logically enough, this instrument was originally termed a hygro-

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the cake will evaporate into the air until it is at equilibrium, leaving a lower moisture content and a disappointingly stale cake. Conversely, biscuits are best enjoyed in a relatively dry state which creates the subtle crunch of the classic digestive. This moisture content corresponds to a relative humidity significantly below typical ambient, so when left out they take up moisture as they tend towards equilibrium. In Ireland, Jaffa Cakes are classified as a cake by Revenue because their moisture content is greater than 12 per cent. At the risk of irritating the more adventurous bakers reading this, cakes and biscuits are generally made from the same basic ingredients – flour, fat, and sugar. An important difference with biscuits is the higher proportion of sugar, which increases the hygroscopicity. From all this we can also understand what happens to those foolish enough to store cakes and biscuits in the same tin; essentially the moisture in the cakes migrates to the biscuits, ruining both. Hypothetically, a

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



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