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LETI: 33,000 NET ZERO CARBON HOMES PLANNED
Plans for over 33,000 net zero carbon new homes are underway across the UK, Passive House Plus can reveal.
Data collated by the London Energy Transformation Initiative (LETI) indicates that 33,000 homes at master planning level are set to be designed to meet key performance indicators for scalable net zero, as defined by LETI – meaning they are highly energy efficient, such that they are using their fair share of the UK’s predicted renewable energy supply. LETI told Passive House Plus a further estimated 2,500 homes currently at stage two to four (post planning but pre construction) are also set to meet the key performance indicators.
The LETI net zero carbon definition includes a total energy use intensity figure for energy consumed at the meter. The figure varies based on building type, ranging from 35 kWh/m2/ yr of gross internal area for dwellings, to 55 and 65 kWh/m2/yr for commercial offices and schools, respectively. LETI describe this as the maximum energy budget for the building, to enable a decarbonised grid to meet the remaining demand. The net zero carbon target also includes a space heating demand of 15 kWh/m2/yr. “It’s essentially building to the passive house standard with a heat pump,” said LETI’s Clara Bagenal George, adding that LETI’s targets were for in use energy, rather than just for calculated energy use.
LETI’s rise has been little short of meteoric. While this may seem a remarkable phenomenon given the organisation’s voluntary, decentralised nature, Bagenal George cites these very characteristics as being essential to its success. “It wouldn’t have worked if it was a top down approach,” she said. “Our collaborative approach has fostered much more of a sense of ownership of the targets across the network.”
The group was set up to work collaboratively to put together evidence-based recommendations for two pieces of policy – the new London Environment Strategy and the rewrite of the London Plan. In the absence of clear, credible statutory targets for net zero carbon buildings, LETI decided to set its own, preparing a one page definition of net zero carbon in December 2019, and the LETI Climate Emergency Design Guide in January 2020. “We thought we needed to define good,” said Bagenal George. “We’ve been astounded by the response. I think it shows the collaborative approach works, rather than just a centralised approach.” LETI subsequently played a key role in mobilising engagement in the consultation process for the Future Homes standard.
Bagenal George said LETI began the process of collating numbers on projects so that other built environment professionals can point to the explosion of construction projects being designed to LETI’s net zero carbon targets. •
(above) A rendering of a 600 unit net zero carbon passive house development planned for York City Council’s housing delivery programme. Designed by Mikhail Riches, who won the Stirling Prize for the Goldsmith Street passive certified social housing scheme in Norwich, the new scheme also features air source heat pumps and PV arrays, and may be an early example of the kinds of schemes built in accordance with the LETI’s net zero carbon performance indicators.
Poorly ventilated retrofits can double radon retrofit risk, study finds
Residential retrofits must ensure ventilation is carefully considered in order to avoid an increase in radon gas levels, researchers at NUI Galway in Ireland have found.
A team from the university’s school of physics conducted one of the first studies of its kind to quantify the impact of improved energy efficiency and airtightness on radon – a radioactive, odourless, colourless and tasteless gas that is a leading cause of lung cancer.
The modelling showed that if appropriate ventilation measures were not considered during the retrofitting process, there is a potential for radon levels to more than double.
However, the study also showed that when appropriate ventilation measures were implemented, radon concentrations could be reduced below initial levels. This finding is consistent with other evidence indicating that certain approaches may in fact reduce radon risks. As previously reported in Passive House Plus, a 2020 monitoring study led by Barry McCarron found significantly lower radon levels in passive houses – which combine mechanical ventilation with heat recovery and advanced airtightness levels – than in neighbouring properties.
The new study was carried out by Dr James McGrath and led by Dr Miriam Byrne as part of research funded by Ireland’s Environmental Protection Agency. It has been published in the international journal Building and Environment.
“The research findings highlight that radon, and indoor air quality overall, needs to be given due consideration as a key element of any proposed retrofitting works,” James McGrath said.
Radon is responsible for about four per cent of lung cancer deaths in the UK each year. The study, ‘Factors influencing radon concentration during energy retrofitting in domestic buildings: A computational evaluation’, is available online at tinyurl.com/ NUIGradon. •
Green groups critical of latest budget
Leading environmental and green building charities have criticised the government’s lack of ambition on retrofit, upskilling and a green economic recovery in its latest budget.
“With just eight months until the UK hosts COP26 in Glasgow, this was a missed chance for global green leadership,” Harriet Lamb, chief executive of Ashden, the UK-based climate charity, said in response to the budget, which was announced by chancellor Rishi Sunak on 3 March.
“Where was the plan to retrofit our cold, old homes – or our public buildings such as schools where young people are crying out for climate action? There was not a squeak about the Green Homes Grant which has struggled because we do not have the people trained in the right skills and government is not offering long term certainty to companies.
“We have 96,000 gas engineers but just 750 accredited heat pump engineers and only 500 retrofit coordinators; and only 5 out of 200 FE colleges offer dedicated courses in renewable energy. This was the moment to score the twin goals of creating jobs and laying the foundations of the green economy – and the chancellor missed it.”
The UK Green Building Council (UKGBC) echoed these sentiments, especially regarding the uncertainly over the Green Homes scheme. “We are still none the wiser about the fate of the Green Homes Grant scheme, which just a few short months ago the Chancellor told us would support over 100,000 jobs in green construction up and down the country,” said chief executive Julie Hirigoyen. “UKGBC, together with many others in our industry, have strongly advocated that the £1.4bn of unspent funding be rolled over to 2021/22, but today’s budget leaves both industry and householders still in the dark.
“Beyond the opportunities for green investment offered by the Infrastructure Bank and new green gilt and retail savings product, this budget appears to ignore the huge part that greening our buildings can play in delivering our post-Covid economic recovery. Tackling carbon emissions from buildings – particularly the existing housing stock – is not easy, but we cannot afford to duck the challenge any longer.
“The chancellor’s ‘investment-led’ green recovery should not ignore the voice of the industry calling for a national retrofit strategy to unlock vital green jobs across the whole country.” •
(above) Chancellor of the Exchequer Rishi Sunak holding up the red box on budget day. Photo by Harriet Pavey/No 10 Downing Street.
AECB launches new retrofit standard
The Association for Environment Conscious Building has announced the launch of the new AECB Retrofit Standard, which like its AECB Building Standard, is based on the passive house standard and designed to promote a whole-house, fabric first approach.
The standard requires buildings to demonstrate a space heating demand of less than 50 kWh/m2/yr — though up to 100 kWh/m2/yr may be allowed with a special exemption — and a maximum airtightness of 2 air changes per hour (at 50 Pa).
While based on modelling in the Passive House Planning Package (PHPP), the AECB Retrofit Standard allows for self-certification. Projects can be self-certified through the client engaging an architect, engineer or other experienced consultant, or a suitably experienced contractor. For certification, evidence must be uploaded to the AECB Low Energy Buildings Database.
Writing about the launch of the standard at enhabit. uk.com, Dr Sarah Price, head of building physics at Enhabit and new technical author of the British Standards Institution's PAS 2035 retrofit standard, said that while the Passive House Institute’s Enerphit standard is a brilliant aspiration, “it can often be can often be unattainable and maybe too stringent for most homes in the UK”. (Enerphit requires a maximum space heating demand of 25 kWh/m2/yr).
She continued: “The AECB Retrofit Standard offers a pragmatic approach to the energy demand targets, which are still potentially lower than current UK new building regulations. The main difference that sets the AECB standard apart is that it recognises that every home is unique, and focusses on managing retrofit risks to avoid unintended consequences.
Compliance with the AECB Retrofit Standard requires the building has been modelled in PHPP, construction quality has been verified and the supporting data has been publicly declared. Delivering the AECB Retrofit Standard also relies upon minimising thermal bridges using a PHPP verification sheet and following MVHR and airtightness testing protocols.
Meanwhile, the AECB’s popular and fully online AECB CarbonLite Retrofit training course is being complimented by a new retrofit co-ordinator training course. This will allow students to gain a level five diploma in retrofit coordination and risk management. For more see www.aecb.net. •
Denmark sets out phased embodied carbon targets for buildings
Timetable for phasing in and tightening of CO2e requirements New buildings over 1000 m2 New buildings under 1000 m2
Requirement for LCA calculation
Voluntary CO2e grade
2023
By end of 2023
2025
By end of 2025
CO2e limit corresponding to 12 kg CO2e/m2/yr
CO2e limit corresponding to 8 kg CO2e/ m2/yr The parties to the agreement will meet with a view to determining the limit value from 2025, so that this can be determined from the latest knowledge and data. CO2e requirements limit value determined on the basis of the most recent knowledge and data. With a requirement of e.g. 10.5 kg CO2e/m2/yr, approx. 1/3 of new construction should perform better climatically than currently. CO2e limit corresponding to 7 kg CO2e/ m2/yr
Parties to the agreement will meet to set a limit from 2027, so that this can be determined from the latest knowledge and data.
2027
CO2e requirements limit value determined on the basis of the most recent knowledge and data. With a requirement of e.g. 9 kg CO2e/m2/yr, approx. 3/4 of new construction should perform better climatically than currently. End of 2027 Parties to meet to set a limit value from 2029 CO2e limit corresponding to 6 kg CO2e/ m2/yr
2029
CO2e requirements limit value determined on the basis of the most recent knowledge and data. With a requirement of e.g. 7.5 kg CO2e/m2/yr, approx. 9/10 of new construction should perform better climatically than currently. CO2e limit corresponding to 5 kg CO2e/ m2/yr
Denmark is set to introduce embodied carbon targets into the country’s building regulations, a policy which has been backed with cross-parliamentary support.
The National Strategy for Sustainable Construction constitutes the government's action plan for the construction sector, and builds on a number of policy agreements, concluded since the current Danish government formed in 2019, to reduce construction emissions and help achieve the country’s 70 per cent reduction target by 2030.
The policy sets out a staged phasing in and tightening of embodied CO2 targets for buildings, including separate requirements initially for larger and smaller buildings. Buildings below 1,000 m2 will initially only be required to calculate the life cycle assessment (LCA), while buildings over 1,000 m2 will also be required to meet embodied CO2 equivalent (CO2e) limits, which includes CO2 and other greenhouse gases converted into equivalent values of global warming potential.
The policy will also include more ambitious voluntary targets, building on the test phase of the voluntary sustainability class in 2020, which includes a requirement for LCA calculation.
The policy is all the more remarkable in that it was backed with cross-parliamentary support, including the Social Democrat-led coalition of centre left, left and socialist green parties, as well as all main opposition parties, including centre right and populist right parties. The negotiation of the agreement among such a broad range of political parties should ensure its stability, with the parties to the agreement committing to meeting again in 2023, 2025 and 2027 to tighten embodied CO2e targets based on the latest knowledge and data.
The announcement follows progress from a number of European countries in tackling embodied carbon, which is estimated to contribute 11 per cent of global greenhouse gas emissions annually. The Netherlands was the first country in the world to require life cycle assessments on new buildings, in a regulation which came into force in January 2013, with France and the Nordic countries subsequently developing regulations on embodied carbon in buildings. •
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