The Welsh Government recently released a publication which summarises the consultation feedback on the proposed changes to Part L regulations. The consultation ran from the 26th August to the 17th November 2025 and had a total of 88 responses.
Two options for new homes were discussed in the consultation. Once all responses were considered the preferred option (Option 1) was chosen to be the appropriate next step in energy efficiency standards for the upcoming Part L 2025 standard. As this option provides a balance between good performance and capital cost whilst still being an achievable minimum standard with significant energy and carbon savings.
Small changes were made to the option 1 specification in response to suggestions made, these changes include:
- External Wall U-value: From a proposed U-value of 0.15W/m2.K to an improved U-value of 0.13W/m2.K.
- Renewable energy generation will now be a requirement within schedule 1 (Part L) of the building regulations
- The Approved document L notional dwelling specification guidance text will be amended so that all other heat pump technologies such as hydronic, air-air systems, ground source and water source heat pumps will in general also offer near equivalent or better efficiencies.
- Dwelling energy efficiency rate (minimum EPC: B) will be replaced with energy use intensity for new homes. Will not be introducing Fabric energy efficiency rate like England
- SAP 10.3 will be used until Home Energy Model is ready
- 1 year implementation period (between release in, spring 2026 and when regs come into effect, spring 2027)
This document shows a shift away from fossil fuel heating systems and towards fabric first, low carbon heating, and renewable generation.
It is expected that the amendments to regulations will be in spring 2026 and will be coming into effect spring 2027.