Improve fabric, airtightness and thermal bridging performance under the new building regulations
Updated: 26 June 2022
Find out how the ‘Part L’ building regulations for thermal conductivity and air permeability have changed.
- Compliance is required if building in England under new regulations which came into force on 15 June 2022.
- Scotland,
Wales and
Northern Ireland are introducing their own changes.
Check new fabric standards
You must now meet stricter minimum standards so the new homes you build use less energy and produce lower carbon emissions.
The new regulations for thermal conductivity limit U-values in the following fabrics:
| Existing regulations | New regulations from 15 June 2022 | |
|---|---|---|
| Roof | 0.20 W/(m2K) | 0.16 W/(m2K) |
| Wall | 0.30 W/(m2K) | 0.26 W/(m2K) |
| Floor | 0.25 W/(m2K) | 0.18 W/(m2K) |
| Window | 2.00 W/(m2K) | 1.6 W/(m2K) |
The U-value for rooflights has changed from 2.00 W/m²K to 2.20 W/m²K.
You can still use an average target fabric energy efficiency rate (TFEE) for new blocks of flats and terraced houses instead of individual rates for each home.
Check new airtightness standards
The new regulations still allow passive rather than mechanical ventilation.
However, highly airtight homes with an as-built air permeability of less than 3.00 m3/(hm²) at 50 Pa will require some form of continuously running mechanical ventilation.
The new regulations lower the air permeability limit by 20% to 8.00 m3/(hm²) at 50 Pa for natural ventilated buildings.
However, a lower level of air permeability will inevitably be required to meet the overall
Fabric Energy Efficiency Standard (FEES).
The notional dwelling specification (which compares airtightness performance in SAP) has not changed. This remains at 5.00 m3/(hm²) at 50 Pa.
You must
carry out air permeability tests on all new homes.
Check thermal bridging standards
You must consider thermal bridging throughout your design process and use products which reduce its impact.
According to Building Research Establishment (BRE) thermal bridging can cause up to 30% of heat loss.
You must keep drawings of all the different construction junctions and make them available to SAP assessors and local building control.
Find out more about the importance of thermal bridging.
Record your design decisions
You must document your decision-making throughout your design process.
Use this documentation to show SAP assessors and local building control your decisions and how your designs meet the new regulations.
Find out how to provide information for SAP assessors and building control.
Keep up to date
Use the Future Homes Hub to keep up to date with changes to the building regulations and the introduction of the Future Homes Standard.
Check what you need to do to meet the new regulations through our
detailed guides.
Find out more
Find new regulations in the official Approved Documents on GOV.UK:
- Conservation of fuel and power: Approved Document L - ‘Part L’
- Overheating: Approved Document O - ‘Part O’
- Ventilation: Approved Document F - ‘Part F’
We welcome your feedback on this page. Please report any problems, and let us know if there are particular areas where further guidance would be useful.