ROUND TABLE REPORT 27
BUILDING INDUSTRY INSIGHT
(L-R) David Clarke of IDSystems, Tzeh Bin Cheong of Shepheard Epstein Hunter, Bill Hayward of Schöck, and Chris Carr of Carr and Carr Builders, discuss Part L in depth Photos © Tom Boddy
to reach net zero carbon emissions in 2050. 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 of TODD Architects told the group that – similarly to Hawkins\Brown – working in London residential schemes has meant that his practice has already been designing 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.” Chris 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 commitment
ADF JULY/AUGUST 2023
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%
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