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The Welsh Government has released a consultation that looks to change Approved Documents Part L, Part O and Part F. These changes follow in the footsteps of the Future Homes Standard policy in England.  

The consultation is open until 17th November, and the updated regulations are likely to be confirmed in the first half of 2026. They are expected to be implemented before the end of that year.  

Why This Matters  

The proposed changes mark a clear move towards aligning Wales’ building regulations with Net Zero targets. By moving to an Energy Use Target and emphasising low-carbon technologies (like heat pumps, PV and MVHR), the proposals set a high bar for energy performance.  

Key Proposals  

Part O Overheating  

There are plans to extend the reach of Part O. Overheating assessments may be required for loft conversions and glazing replacements in existing blocks of flats. 

Energy Performance EPC to EUI 

Wales currently has a minimum EPC rating for new dwellings. The consultation proposes scrapping this requirement and replacing it with an Energy Use Intensity (EUI) target. 

Photographic Evidence  

Photographic evidence may be extended to cover newly built non-residential buildings, rather than just dwellings.    

Home Energy Model (HEM) 

HEM will replace SAP for calculating compliance with the new part L targets. A transitional stage using SAP10.3 has not been confirmed, but it is mentioned as a potential fallback if HEM is not ready. 

Part L Compliance  

Two notional specifications are under consideration for Part L Compliance. Both follow the FHS approach, assuming the use of heat pumps and PV panels to achieve targets.  

The stricter option also includes MVHR ventilation and a notional air test of 1.5.  

Under either approach, gas boilers are not expected to meet the new requirements.  

Extensions and Non-Residential Buildings  

Large domestic extensions may be required to include PV panels.  

SBEM calculations for non-residential buildings will need to account for low-carbon heating and PV. While methodology changes are minor, notional specifications will include lower energy and emissions targets.  

Implementation Timeline  

Consultation Closes: 17th November 2025  

Final Text Confirmed: First half of 2026 

Regulations Implemented: End of 2026 

Next Steps for the Industry  

It is important to review these proposals early, as they  are likely to influence design, specification, and compliance processes. 

You can read the full consultation and submit responses here: Building Regulations Part L: 2025 review | GOV.WALES 

This consultation introduces some of the most significant updates to Welsh building regulations in recent years and responding to the consultation is an important opportunity to help shape building compliance in Wales.