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ROUND TABLE REPORT
were using air source heat pumps within their solution to meet Part L, as against 30% gas boilers and PV, with the remainder selecting a hybrid approach. The heat pumps lobby assert that the required efficiencies will only be realised with a low U-value fabric. Windows, insulation, and thermal breaks – all fundamental components of that fabric – were all represented by our three sponsors. David Clarke at IDSystems admitted that across the glazing industry generally, “products are designed to meet the regulations, not to go far in excess,” which could raise issues around Future Homes Standard compliance. He added that the “historic” tendency of choosing the most cost-effective product “is now having to change.”
Bhardwaj said that architects should be looking at thermal bridging, U-values and window ratios anyway, “as first principles of passive design.” Chris Carr said that installation was the key, and when he was at the Zero Carbon Hub, it identified that thermal bridging was “the one thing that was failing dramatically” in terms of as-built performance. Regarding poor installation, Chris Perry said that “it is the most frustrating thing when you go to site and can see gaps between insulation sections,” adding “it makes it all a bit pointless.” Carr said that his housebuilding firm was now getting joiners to install PIR insulation, as bricklayers “just want to lay bricks and blocks.” Blackham echoed David Clarke of IDSystems, saying that delays to getting products tested was hampering results across the sector on energy efficiency. As well as the limited number of testing sites, he said “we’ve got the June 2025 deadline of CE marking no longer being recognised,” although the new UKCA mark “was exactly the same as a CE mark.” David Clarke agreed that the lack of testing facilities was also causing major challenges for firms looking to supply the ‘net zero ready’ homes required by the 2025 Future Homes Standard.
Responding to demand
Chris Carr said as an SME housebuilder he took a slightly different approach to the ‘fabric first’ mantra – “We’ve gone design first, fabric second,” in the interests of delivering what customers want. He explained: “We’re looking at building houses ‘from the inside out’ – we need to know what we can do inside, including in terms of floor space, before we look at the facade.” He mentioned an ongoing development which had outline planning for 240 homes but his firm is looking to build 137 in order to offer the space that customers want.
Shikha Bhardwaj from Hawkins\Brown said that one of the remaining issues was that the housing sector is talking about U-values, net zero and PVs, “but is not actually talking about the comfort of the occupants, which is absolutely essential.” She said that just focusing on heat pumps was counterproductive to creating a product that consumers will buy into: “They are part of the strategy, not the strategy, and step one is to better understand what the occupants want.”
The cost of Part L & zero carbon In our 2022 Industry Viewfinder audience survey conducted by Housebuilder and Developer magazine on Part L, 65% of respondents thought that added cost was the biggest challenge, and the estimated average £10,000 extra per unit would be passed on to customers by 77% of respondents. Chris Carr said that the cost increase would actually be 10% per house for his firm (around
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“It’s very easy to put a figure down and say this is our Passivhaus target, but how does that actually translate into construction?” Shikha Bhardwaj, Hawkins\Brown
£30K-£40K), which is much more than estimates which have put it as low as 3.6%.
The quality of installation is clearly at the core of ensuring that fabric measures have the desired result, particularly in terms of customer confidence, which was damaged again following botched Green Deal installations. Simon Blackham said that in order to make things easier for installers, Recticel introduced a tongue-and- groove full-fill PIR board solution which has become a major part of its domestic business. It is designed to be simply installed in narrower cavities than would normally be required to achieve that U-value level.
Chris Perry pointed towards the Future Homes Standard and the likely cost uplift of making ‘net zero’ homes, saying his research had found that it was “around 15-20%” currently. In addition, research has shown that homeowners “are willing to pay 10% more for a zero carbon home,” and “the value it adds is really more than that.” He added: “Imagine we were in a tech industry, there’d be so much development into reducing the costs, because it’s something people want and are willing to pay for.”
Chris Carr however said that more of his customers needed to be persuaded, and David Clarke of IDSystems cautioned that for self- builders, “if you present them with the more expensive thermally efficient option and a bog standard one that meets requirements, unless they are going for Passivhaus they’ll find an argument to go for the cheaper option.”
Part L vs. Part O Shepheard Epstein Hunter’s Tzeh Bin Cheong reiterated that although architects were keen to focus on orientation and passive approaches as part of addressing Part L, Part O was where the major issues were arising. “We need to consider external noise and pollutants,” he said, particularly concerning urban sites. He added: “When there’s a noise issue or pollution, we tend to say ‘these are non-opening windows,” but Shikha Bhardwaj pointed to cleaner air in future with the exponential growth of EV usage. She also mentioned that the industry “needed to have a
ADF JULY/AUGUST 2023
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