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INDUSTRY VIEWFINDER: A NEW ERA OF ENERGY EFFICIENT BUILDINGS
“What are the most critical areas to focus on when designing to the new Part L in residential properties?”
for renovations and extensions to existing buildings. Part L1B states that if a ‘thermal element’ (roof, wall or floor) is replaced or renovated, it must be done to Part L1A standard. Part L changes for domestic refurbishment include a max window U-value of 1.4 W/m2K, new roofs and extensions to have no higher than 0.15 W/m2K, and refurbished roofs no higher than 0.16 W/ m2K. In extensions, it’s a maximum 0.18 W/m2 for walls, and 1.4 W/m2 for doors, windows and rooflights. Primary energy and FEES are to be used for whole house energy use calculations in extensions, and SAP compliance is required.
SAP & the notional building
New homes will now be assessed under a new Standard Assessment Procedure (SAP) calculation – SAP10. This sets requirements for higher levels of insulation, as well as a new Primary Energy metric. The main change within the new SAP (10.2) is that the carbon weighting within the TER (Target Efficiency Rate) is now different so that electricity now has a lower ‘carbon factor’ than gas. The new 2021 Part L also added the ‘Primary Energy’ rate to TER and TFEE (Target Fabric Energy Efficiency) to make up a fuller picture of the building’s energy use within the overall 31% emissions reductions target. There were however other, more challenging jumps to make for architects, clients and contractors and the whole supply chain in terms of design and workmanship, as our survey bears out. The notional building is a hypothetical dwelling used in
SAP to calculate the TER and TFEE, and based on the same geometry and orientation as the proposed ‘real’ building – but with default ‘reference values’ for various build elements. There is scope for design flexibility under the new Parts L and F; as long as the required TER is achieved, the ratios of how it is achieved within the various elements of the building are down to the project team in each individual case.
Assessing the problem Levels of understanding In surveying our architect readership, we wanted to initially discover their levels of understanding on all three new regulations (the updated Parts L and F, but also the new Part O). A healthy 9% believed they had a ‘very good’ understanding of the Part L changes, however 12% said their understanding was ‘poor.’ Part F fared less well, with 6% saying they had ‘very good’ understanding, and 3% describing their level as ‘very poor.’
Unsurprisingly given it being introduced in 2022, Part O was only seen to have ‘very good’ understanding by 5%, with 7% admitting their understanding was ‘very poor.’ The majority of respondents however graded their understanding as ‘acceptable’ across all three standards.
When it came to specific key areas of Part L, level of understanding ratings varied somewhat. The new reports required to show onsite compliance (‘BREL’ for residential
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ADF FEBRUARY 2023
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