The Welsh Government has published a consultation version of Approved Document L Volume 1 for dwellings, which sets out guidance on complying with the energy efficiency requirements of the Building Regulations 2010 in Wales. The document is dated 2025 and marked "Consultation version. Not statutory guidance"1. It accompanies a 2025 consultation on Part L, Part F and Part O of the Building Regulations in Wales, on which the Welsh Government is seeking views covering standards for new and existing domestic and non-domestic buildings1.
The central proposal concerns the calculation methodology. The document states: "The consultation proposes the use of the Home Energy Model (HEM) replacing SAP"1. SAP, the Standard Assessment Procedure, is the methodology currently used to produce energy performance ratings for dwellings, and the assumptions behind home energy ratings feed into EPCs and compliance calculations. The Home Energy Model is put forward here as its replacement in this context.
The document is described as the 2025 edition and as taking effect on "TBC 2026" for use in Wales, a date that is not yet fixed1. It does not apply to work on a particular building where a building notice, full plans application or initial notice has been submitted before that date, provided the work for each building is started before TBC 20261. The document says full detail of the transitional arrangements can be found in Circular Letter 00?/2026 published on the Welsh Government's building regulations pages, a reference that is itself incomplete in the consultation text1.
The guidance in Volume 1 applies to dwellings only, with newly constructed dwellings covered in Sections 1 to 141. In a mixed-use building, Volume 2 should be consulted for building work in parts that are not dwellings1. The document notes that compliance with approved document guidance "does not provide a guarantee of compliance with the requirements of the regulations", and that anyone preferring another route to meeting a requirement should agree this with the relevant building control body at an early stage1.
"This approved document takes effect on TBC 2026 for use in Wales."
The consultation version also records that Section 3, on considering high-efficiency alternatives, has been removed "in line with the proposal to revoke regulation 25A"1. Changes relative to the Approved Document L Volume 1, 2022 edition incorporating 2024 amendments are highlighted in yellow in the consultation text, with consultation-only notes in red1.
| Item | Detail as given |
|---|---|
| Document | Approved Document L Volume 1, dwellings, 2025 consultation version |
| Status | Consultation version, not statutory guidance |
| Proposed methodology | Home Energy Model replacing SAP |
| Proposed effect date | TBC 2026, for use in Wales |
| Transitional protection | Work where notice or application submitted before that date, started before TBC 2026 |
| Removed section | Section 3, high-efficiency alternatives, linked to proposed revocation of regulation 25A |
Why it matters for households
The methodology behind a home's energy rating determines what a rating means and what a householder is told about a property. If the Home Energy Model replaces SAP in Welsh compliance calculations, the basis on which new and renovated dwellings are assessed changes, and the numbers attached to a home's performance may not be directly comparable with those produced under SAP. For a householder, the practical effect sits in the paperwork: compliance evidence, ratings and the assumptions behind them. The consultation is a proposal, not a decision, and the effect date is given only as TBC 2026. The consultation process is where such changes are proposed, decided and changed, and this document is one input to it. Because the guidance applies to Wales, it sits alongside the separate building regulations for England, Scotland and Northern Ireland, and within the wider set of energy and buildings policy in Wales.
What happens next
The document is a consultation version and is not statutory guidance1. The Welsh Government is seeking views on the standards for new and existing domestic and non-domestic buildings guidance1. The effect date is given as TBC 2026, and the transitional arrangements are said to be set out in Circular Letter 00?/2026, a reference that is incomplete in the consultation text1. No closing date for the consultation, and no confirmed implementation date, has been reported in the document.