The Welsh Government has issued a consultation version of Approved Document L Volume 1, the guidance covering the energy efficiency requirements for dwellings in Wales. The document is marked "Consultation version. Not statutory guidance" and accompanies a 2025 consultation on Part L, Part F and Part O of the Building Regulations in Wales1. It is dated 2025 and carries the label "2025 edition"1.
The draft states that it "takes effect on TBC 2026 for use in Wales", with the month and day still to be confirmed1. It would 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 the same point; the document says full detail of the transitional arrangements will be found in a circular letter, numbered with a placeholder, published on the Welsh Government's building regulations pages1.
The consultation proposes replacing the Standard Assessment Procedure with the Home Energy Model: "The consultation proposes the use of the Home Energy Model (HEM) replacing SAP."1 The draft also notes that Section 3, on considering high-efficiency alternatives, has been removed in line with a proposal to revoke regulation 25A1. Paragraphs changed relative to the Approved Document L Volume 1, 2022 edition incorporating 2024 amendments are highlighted in yellow, and notes that apply for consultation only appear in red text1.
The volume applies to dwellings only, with newly constructed dwellings covered in Sections 1 to 141. In a mixed-use building, Approved Document L Volume 2 should be consulted for building work in parts that are not dwellings1. Parts of a building that are not heated, such as garages, carports and outbuildings, are exempt1. Conservatories and porches are exempt where they are at ground level, have an internal floor area of less than 30 m2, are thermally separate from the heated area of the dwelling, and contain no fixed heating appliance or extension of the building's heating system1.
The draft sets out the limits of approved document guidance. It states that "compliance with the guidance set out in the approved documents does not provide a guarantee of compliance with the requirements of the regulations", and that anyone preferring another route to a relevant requirement "should seek to agree this with the relevant building control body at an early stage"1. It also notes that work to some dwellings does not need to comply fully with the energy efficiency requirements where doing so would unacceptably alter the dwelling's character or appearance, and that such work should comply with the standards "to the extent that it is reasonably practicable"1.
"This approved document takes effect on TBC 2026 for use in Wales."
Why it matters for households
Approved Document L Volume 1 is the document that builders, designers and building control bodies work to when demonstrating that a new or altered dwelling in Wales meets the energy efficiency requirements of the Building Regulations 20101. A change of calculation method from SAP to the Home Energy Model would alter how a home's predicted energy performance is worked out and reported, which is the basis on which fabric, glazing, heating and ventilation choices are assessed at design stage1. For a household, the practical link is that the same dwelling design can produce different modelled figures under a different method, and the method shapes what a builder must install to show compliance.
The draft also confirms the position of work on existing homes. Thermal elements, renovations and replacements, consequential improvements and change to energy status are dealt with in Section 12, and consequential improvements in Section 131. Conservatories and porches below 30 m2 that meet the thermal separation and heating conditions sit outside the full requirements1. The document repeats that following approved document guidance is not a guarantee of compliance, and that alternative approaches should be agreed with building control early1.
Because the document is a consultation version and not statutory guidance, none of it currently imposes requirements1. The rules that apply today in Wales are those in the published Approved Document L Volume 1, 2022 edition incorporating 2024 amendments, which the draft says changes should be reviewed alongside1.
What happens next
The consultation seeks views on the standards for new and existing domestic and non-domestic buildings guidance1. The draft is scheduled to take effect in 2026, with the exact date to be confirmed, and transitional arrangements are to be set out in a circular letter on the Welsh Government's building regulations pages1. The circular letter number is given as a placeholder in the consultation version1.