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INSULATION Element Type
Area Weighted Limiting U-Values
All roof types (W/m2K) 0.16 Walls (W/m2K) Floors (W/m2K)
Party wall (W/m2K) Windows (W/m2K) Doors (W/m2K) Air permeability Ventilation
Heating appliance Heat emitters WWHR Photovoltaics
0.26 0.18 0.2 1.6 1.6
N/A N/A
N/A N/A
N/A N/A
U-VALUES Worst case area weighted U-values and notional dwelling specification for new dwellings (ADL1 2021)
Notional Dwelling Specification
0.11 0.18 0.13 0
1.2 1
5.00 m³/m²/Hr@50Pa. Natural with extract fans 89.5% gas boiler*
*new systems must meet 92%
Design flow temperature = 55°C
Yes 40% of ground floor area / 6.5
This means a slimmer thickness can often be used to achieve the desired U-value. Rigid insulation materials such as phenolic boards can achieve thermal conductivities as low as 0.018 W/mK, making it possible to reduce the depth of constructions, and so realise more internal space, without compromising on thermal performance.
Thermal bridges
In addition to setting tougher FEES targets, ADL1 2021 also makes key changes to how heat losses from thermal bridges are considered. Thermal bridges are areas where materials which are more conductive to heat than the insulation layer form a path between the inside of the property and the outside. These commonly occur in areas such as around windows and doors and at junctions between building elements. These paths can form a fast-track for heat to escape and have been shown to account for as much as 30% of total losses. To improve practice in this area, the Accredited Construction Details (ACDs) have been removed as it was felt they had become outdated. The default heat loss values given where no detail is supplied (either for the junction or globally for the building) have also been tightened. This makes it much more difficult to reach compliance with the FEES target without either having bespoke details calculated, or making use of details from manufacturers or industry libraries.
WWW.ARCHITECTSDATAFILE.CO.UK
By paying close attention to details, architects can strengthen
specifications and close the performance gap
Compliance reports
In addition to encouraging the adoption of bespoke details, the revised regulations also include new BREL Compliance Reports with similar BRWL to be introduced in Wales. Project teams need to provide both a design stage and ‘as-built’ report. The BREL design stage report requires key aspects of the property SAP model to be documented and signed off by an energy assessor. This includes the details and psi-values for key junctions within the building such as sills, jambs and eaves. The as-built report should detail any changes from the original specification or details and be supported with photographs of the insulation measures taken by the installers before junctions are covered, to prove that the materials fitted match the specification and have been installed correctly. The finished report will be submitted to Building Control, and deviations could lead to a building being found to be non-compliant, resulting in costly remedial work. This is a key change for architects, as it can help to strengthen initial specifications. Factors such as the insulation product’s thermal conductivity and emissivity are incorporated into the Psi-value calculation where bespoke details are used. As a result, the value is non-transferable to a different material. This means that if a different material is going to be installed, the detail would need to be reworked and the SAP model recalculated, making it a much more involved process.
Closing the gap
At a time when heating costs are rapidly rising for everyone, the updates to the Building Regulations are an opportunity to ensure new homes deliver excellent energy performance. By paying close attention to details, architects can strengthen specifications and close the performance gap, providing the best results for occupiers and the environment.
Jon Ducker is head of regulatory affairs at Kingspan Insulation GB
ADF JULY 2022
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