We staged our first industry round table a month before the legal requirement was brought in for all new dwellings to comply with the new Part L of the Building Regulations, which requires them to produce 31% fewer carbon emissions than the previous Regs. This is a step towards the 2025 Future Homes Standard, which will require a much more demanding 75%-80% cut in emissions, meaning major changes to both building fabric, design and integration of renewables and alternatives to fossil fuels.
Our timely event saw representatives from architecture and housebuilding sharing their current issues with Part L, with the sponsors contributing valuable insights on the benefits as well as difficulties being experienced in complying with the requirements. There were also some revealing comments on attendees’ perception of the Future Homes Standard, in terms of both the timeline and the industry’s remaining challenges. We were delighted to have three knowledgeable architects on board from high profile practices – Hawkins\Brown, TODD Architects, and Shepheard Epstein Hunter.
As well as Part L, the updated Part F on ventilation, and the new Part O came under scrutiny, and the required trade offs in order to achieve one standard without failing on the other; increasing U-values generally means treading a narrow path to avoid excessive overheating. The event also saw discussions around challenges in terms of future homes’ aesthetics, while the planning system remains rigid.
Building Insights LIVE offered an unusual opportunity to host a candid discussion around compliance with the new Regs, with specifiers and key suppliers exploring how to harness different aspects of building fabric, as the industry works toward the new FEES fabric standard. The discussion also took data collected from our research in our Industry Viewfinder white papers as a springboard for elements of the conversation.
Everyone involved hailed the first instalment as a great success, and we will be holding more in the future, with the next addressing Solutions for Stormwater Management in October.
Cutting your losses
The first question posed to the panel was whether cutting 31% of emissions as a result of Part L 2021 had been a major headache, in the context of current pressures such as skills, materials supply chain issues, and inflation.
How had our architects found addressing the required 31% cut in emissions in residential schemes so far under Part L? Shikha Bhardwaj from Hawkins\Brown set the bar high, stating that the practice saw net zero carbon “as a starting point.” She said that in projects it was a discussion with clients around whether Passivhaus levels of performance were achievable or not, but that there was “a lack of understanding of the different parameters,” such as around U-values and thermal bridging. Bhardwaj added: “It’s very easy to put a figure down and say this is our Passivhaus target, but how does that actually translate into construction? There’s a lot of aspiration to follow Passivhaus, but it comes with a lot of tests at every layer, and the normal way of construction doesn’t do that.”
Chris Perry remarked that – like Hawkins\Brown – working in London residential schemes has meant that his practice TODD Architects has already been working to a level of performance well beyond that of Part L, as the London Plan requires all new homes to be at a ‘net zero’ level. He asserted that it was normally possible to get to “around 60% of agreement” using fabric improvements, and then “top the rest up with PVs,” and so believed that the 31% cut in emissions in Part L is “easily achieved, at least in theoretical design terms.”
Perry added that “it’s when you get to site that you hit problems,” adding that most of the headaches he had experienced “had come from suppliers, Part O (on overheating, which is naturally impacted by a more energy efficient fabric), and embodied carbon.” Embodied carbon is not explicitly covered in Part L, but reducing it is fundamental to achieving the UK’s legal 2050 net zero goals.
Tzeh Bin Cheong from Shepheard Epstein Hunter alluded to issues experienced on a couple of current London residential projects, where wall thicknesses and other fabric measures had been upped significantly to deliver the London Plan requirements of 35% lower emissions than Part L. He agreed with Chris Perry that the trade-offs between Part L’s stipulations on U-values and the resultant impact on overheating and Part O was “where there was a problem.” He gave the example of a new build residential scheme in Redbridge inherited from another architect, which had gained planning permission but was now being redesigned with smaller windows in order to comply with both the updated Parts L and the new Part O.
Housebuilder Chris Carr asserted that his firm was struggling with the fact that they were “trying to build with materials that were not fit for purpose in some cases.” He explained further, saying that “materials quality and design have not improved with the policy,” i.e. the new central drive to produce much more energy-efficient homes than the industry has been accustomed to.
This issue of a lack of rigour when it comes to skill levels among subcontractors feeds directly into the performance gap between design and build. “Unless we engage them, we are going to have a problem,” he said.
The fabric of society
We asked our attendees to submit comments or questions for discussion during the round table. Simon Blackham from PIR insulation firm Recticel’s ‘starter for 10’ was that fabric-first “should be the default starting-point; a back-to-basics approach that gives a robust, reliable platform for renewables.” However, would improvements to the building fabric alone be a realistic solution for the Part L 2021 requirements, or was including renewables a given?
A 2022 BCIS survey of housebuilders found that nearly 45% 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 £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 conversation about internal heights, as we end up doing designs for 2.5 metres and these heat up quickly.” She added that it’s “a balance between comfort, carbon, energy and what the developer wants.”
The Standard Assessment Procedure (SAP) used by Building Control, and its associated challenges, came up several times during the discussion. This included when Chris Perry said that an unfortunate side-effect of the need to balance policy across various building typologies was making SAP “so opaque,” as a result of “trying to be very flexible.”
Bhardwaj added that her firm worked closely with energy consultants on projects to “find out whether the energy figure they were aiming at is sensible.” She explained further that “In SAP, you can only benefit from a certain U-value up to a certain point; after that it doesn’t make any difference.”
IDSystems mainly works in extensions to domestic properties, and David Clarke submitted a question for discussion, namely ‘where does the balance lie between glazing performance and appearance that is going to be necessary for Part L compliance?’ He told the group that while his customers “have got used to seeing inside-out living and floor to ceiling windows, we know that is not necessarily going to be achievable.”
Bin from Shepheard Epstein Hunter pithily responded: “Our energy consultants keep telling us that anything below the waist in terms of glazing is a waste.” Chris Perry asserted that “the only way of achieving the balance between Part L and Part O, especially with the Future Homes Standard, is modelling and testing.”
He said that an MEP engineer has to be involved “right from the start; the very big housebuilders are already doing this, but at the smaller scale it hasn’t got through.” Shikha added that such modelling data would also be useful for design practices to run in future developments.
Control your emotions: planners & Building Control
Chris Carr suggested that Building Control should be brought into pre-application meetings to help get the balance right between the different standards’ demands: “Planners aren’t interested in how it physically works – you have to educate them on why we are doing certain things that affect the look, such as why we can’t put PVs on the rear of all the properties.”
Shikha Bhardwaj said she believed that planners “needed to change their mindset on how ‘ugly’ a zero carbon home will be.” She added that another frustration with planning teams was that “there’s nobody in the meeting to talk about sustainability.” Chris Perry concurred: “They always say it’s key, central, etc, but they never actually discuss it.”
Bill Hayward added that there was something of a ‘not invented here’ syndrome present: “They need to be prepared to let go of what they know, if it’s a new technology you have to do so much work to get any agreement.” Bhardwaj added that a “quick fix” would be to “hire an external consultant to be in the meetings; there are so many experts out there.”
Looking to the Future (Homes Standard)
The second session of the round table moved onto an attempt to see into the not-too-distant future, namely 2025, when the industry will be required to take a massive jump to produce ‘net zero ready’ homes, in accordance with the Future Homes Standard (FHS).
When it comes to windows, David Clarke of IDSystems candidly admitted that if triple glazing would be required to meet the FHS, some of their current window systems would be “obsolete.” Chris Perry pointed out a further issue around triple glazing in that it significantly adds to a project’s embodied carbon.
Clarke added that with budgets normally under pressure in one-off house projects, it was difficult to persuade homeowners to specify windows ‘future-proofed’ against the Future Homes Standard. “If they’ve got to make a decision between a product that is going to meet the new Building Regs but also potentially what is required with Future Homes, or saving a bit of money, it’s very difficult when it’s something they’re not necessarily going to immediately see the benefit of.”
However, one area where the FHS would lead to a real beneficial change in specification, according to Bill Hayward, was that products would be treated “as part of a system rather than individually. At the moment, you solve one problem, and create another one,” he said. David Clarke concurred, adding: “It’s counterproductive to just aim for that U-value figure, because you may not be taking into account that if you went slightly better, you impact the whole fabric.”
The BSI has found that thermal bridging can lead to up to 30% of heat losses, but there were design challenges. Tzeh Bin Cheong from Shepheard Epstein Hunter said that the practice “did not yet understand the linear cold bridging issue” which has been raised around the Future Homes Standard, when “the larger the volume of the wall insulation, the higher the chance of condensation.”
Shikha mentioned that Hawkins\Brown is upskilling staff on thermal bridging to investigate some of the mysteries including around the software, and Chris Perry cautioned that “massive cavities” can result in needing bespoke ties and other structures which increase embodied carbon.
Chris Carr expressed concern that in-demand bungalow designs were unlikely to be achievable under the FHS, but advocated that brick slips could produce bigger cavities without losing floor area. He’s lobbying the Government to push back the FHS deadline by at least two years, due to concerns from SMEs around obtaining materials in competition with volume housebuilders.
However, for suppliers there are obvious benefits to the jump in performance required: David Clarke said that what were potentially “overly efficient products” which have been on the shelf are now seeing the light of day.
Air source heat pumps are likely to be the de facto space heating solution for the FHS in 2025, as gas is phased out. However, Carr feared that the need to provide photo evidence of installation effectiveness might be the “biggest issue” for housebuilders; “you need to get ducting spot on, but on a building site, it’s whoever’s there first that takes priority.”
Simon Blackham of Recticel said the main issues for delivering the Future Homes Standard were “skills,” and identifying what ‘net zero ready’ actually means. He expressed concern that progress to the Standard was “piecemeal,” and was beleaguered by the five year political cycle. He said that ‘zero bills’ houses are “where we should be going,” given the extent of the climate challenge, but our round table showed there was still a long way to travel on this road before the industry is ready to deliver such performance levels. Bill Hayward, echoing Chis Carr earlier, suggested that “maybe the answer is to reduce what we are trying to achieve; if you try to achieve too much, you end up achieving nothing. Maybe we need to break it down into smaller parts.”
One final moment of consensus around the table, among several others, was that with Government not having “made its mind up” on the way forward, the Future Homes Standard is unlikely to be implemented in 2025, though the industry may be technically able to achieve it.
We would like to thank our round table sponsors IDSystems, Schöck and Recticel for supporting Building Insights LIVE.
RECOMMENDATIONS FROM THE ROUND TABLE
Shikha Bhardwaj: “It’s looking at net zero carbon as a bigger challenge than just focusing on compliance, and instead using compliance as a layer of it, not the entire solution. And we need to focus on comfort.”Chris Perry: “It’s even more the case with Part L and Part O that the early stages of the designs are so important, and you need to have everyone on board to create something that works in a holistic way, and so you don’t come into problems later.”
Chris Carr: “Planners need to work together with Building Control officers, and we need exemplars to share good practice of design and delivery. We also need to delay the Future Homes Standard by two years minimum, due to materials issues.”
Simon Blackham: “There’s a need for clarity; it’s not beholden on manufacturers to approve something which we haven’t designed to be used in a certain way.”