The Welsh Government has confirmed it plans to start the next review of Part L of the Building Regulations in 2023, setting a minimum expectation of a 75% improvement option in carbon dioxide emissions against current Part L 2014 standards for its Part L 2025 standards1. The commitment appears in its March 2021 summary of responses to the Building Regulations Part L and F review consultation, which ran from 19 December 2020 to 12 March 2020 as dated in the document1.
The consultation drew 108 responses. Manufacturers and the supply chain accounted for 30 responses (27.8%), other interested parties 25 (23.1%), builders and developers seven (6.5%), local authorities six (5.6%), volume house builders five (4.6%) and the energy sector five (4.6%). No responses came from building control approved inspectors or energy assessors1.
On the 2025 direction of travel, 72% of respondents agreed with the expectation that a home built to Part L 2025 should produce 75-80% less carbon dioxide than one built to current requirements. Of those who disagreed, 16% of all respondents thought the reduction too low and 9% thought it too high1. The Government's stated position is:
"we plan to start the next Part L review in 2023 with the minimum expectation of a 75% improvement option (compared to current Part L 2014 standards) in carbon dioxide emissions for our Part L 2025 standards"
The document also sets out decisions taken on the 2021 standards. The preferred 37% improvement option was confirmed as the next step up in energy efficiency standards for 2021, in preparation for the envisaged Part L 2025 standard1. Fuel factors will be removed, following agreement from 75% of respondents1. The technology factor will not be introduced at this time, and new homes connected to heat networks will need to meet the full primary energy and carbon emission targets1. Minimum standards from the Compliance Guides will be incorporated into the Approved Documents, an approach supported by 60% of respondents1. Changes to BR 443 were made by the Building Research Establishment following consultation feedback1. Self-regulating devices in new dwellings and building automation and control systems will be introduced, with the vast majority of respondents agreeing to the proposed approach1.
| Measure | Outcome reported |
|---|---|
| Part L 2021 standard | 37% improvement option confirmed |
| Fuel factors | To be removed (75% of respondents agreed) |
| Technology factor | Not introduced at this time |
| Heat network homes | Must meet full primary energy and carbon targets |
| Compliance Guides | Minimum standards incorporated into Approved Documents |
Why it matters for households
Part L sets the minimum energy performance a new home must reach when it is built, so the direction set for 2025 shapes the fabric, heating and running costs of homes delivered from that point. The 75% improvement option, measured against Part L 2014, is the figure the Welsh Government says it will treat as its floor for the next review, and the 2025 standard is expected to rely heavily on heat pumps for low carbon heat1. For a household, the practical difference between a home built to current requirements and one built to the 2025 standard is the amount of energy needed to keep it warm, and how that energy is supplied. The removal of fuel factors means the carbon metric no longer adjusts for the fuel used, so the emissions performance of a home reflects its actual energy demand and supply rather than a weighting1. Homes on heat networks lose the technology factor route and must meet the full targets, which places the compliance burden on the connection rather than the dwelling alone1. The Building Regulations in Wales framework and the wider energy and buildings policy in Wales determine how these standards are set and enforced, while the Welsh Housing Quality Standard covers existing social housing rather than new build. The consultation responses also flagged a gap between predicted and operational performance, with some calling for operational performance targets, testing and monitoring1. That gap matters to a household because the standard is assessed at design stage, not on the energy a home actually uses.
What happens next
The next Part L review is planned to start in 2023, with the 75% improvement option as the minimum expectation for Part L 2025 standards1. No further dates for that review have been reported.