The Welsh Government published Approved Document L 2026 (Conservation of fuel and power and the minimisation of greenhouse gas emissions) Volumes 1 and 2, and Approved Document F, Ventilation, Volume 1, on 7 April 2026. The publication was announced by circular letter WGC 006/2026, issued under the building regulations circulars series1.
"This is a circular letter to announce the publication of a new Approved Document L 2026 (Conservation of fuel and power and the minimisation of greenhouse gas emissions) Volumes 1 and 2, and Approved Document F, Ventilation, Volume 1."
The circular gives no technical content beyond the titles of the documents. The Welsh Government's own page carries no fabric values, airtightness limits, ventilation rates or commencement dates1. Those details are not in the circular, and no Welsh commencement date has been reported in it.
Industry body the Home Builders Federation (HBF) sets out a comparison of Welsh and English standards, describing the Welsh documents as a Future Homes Standard (FHS) for Wales. Its figures put Welsh Part L 2026 external walls at 0.13 W/m²K, ground floors at 0.11 W/m²K, roofs at 0.11 W/m²K, windows at 1.2 W/m²K and doors at 1.0 W/m²K, with airtightness of 4 m³/(h·m²) at 50 Pa2.
| Element | England Part L 2026 FHS | Wales Part L 2026 FHS |
|---|---|---|
| External walls | 0.18 W/m²K | 0.13 W/m²K |
| Ground floor | 0.13 W/m²K | 0.11 W/m²K |
| Roof | 0.11 W/m²K | 0.11 W/m²K |
| Windows | 1.2 W/m²K | 1.2 W/m²K |
| Doors | 1.0 W/m²K | 1.0 W/m²K |
| Airtightness | 4 m³/(h·m²) at 50 Pa | 4 m³/(h·m²) at 50 Pa |
Source: HBF comparison table2. The Welsh Government circular does not publish these values1.
HBF dates the Welsh documents to 7 April 2026, against 24 March 2026 for the English Approved Documents, and gives a Welsh FHS commencement of 4 March 2027 with a transitional period ending 3 March 2028. It records a mandatory photovoltaic announcement in Wales on 27 February 2026 and a second FHS consultation in Wales in August 20252. The Welsh Government circular does not confirm any of these dates1.
On ventilation, HBF states that Part F requirements were introduced on the same timeline as the FHS, with higher ventilation rates intended to maintain airflow as fabric airtightness increases, greater emphasis on decentralised mechanical extract ventilation (dMEV) and mechanical ventilation with heat recovery (MVHR), and building control approval required before occupation. Ducts over 2m in length would require full accompanying designs approved by building control2. The Welsh circular does not describe these requirements1.
Why it matters for households
Approved Document L governs how much energy a new home may use for heating, hot water and lighting, and how much heat it may lose through its fabric. Approved Document F governs how that home is ventilated. For a household buying or occupying a new home in Wales, these documents set the fabric and ventilation the home is built to, and therefore the baseline for how much energy it takes to keep warm and how fresh air is supplied once the home is airtight.
The HBF figures indicate Welsh new build fabric standards at least as tight as those proposed for England, with lower wall and floor heat loss values and the same airtightness target2. Tighter fabric reduces heat demand, but it also means ventilation has to be designed and commissioned rather than left to incidental draughts, which is why Part F is published alongside Part L. For a household, the practical difference between a well commissioned system and a poorly commissioned one is air quality and running cost, not just comfort.
The documents apply to new homes. They do not change the rules for existing homes, and nothing in the circular or in the HBF material alters obligations for households in homes already built1.
What happens next
HBF gives a Welsh FHS commencement of 4 March 2027 and a transitional period ending 3 March 2028, with the mandatory photovoltaic announcement dated 27 February 20262. The Welsh Government circular announcing publication does not state a commencement date or transitional arrangements1. Where the two differ, the circular is the Welsh Government's own statement and the dates above are HBF's account.
Sources2 cited
- Publication of Approved Document L (2026) Volumes 1 and 2, and Approved Document F, Ventilation, Volume 1 (WGC 006/2026) | GOV.WALES, gov.wales
- [](https://www.hbf.co.uk/news/future-homes-standard-april-2026/), hbf.co.uk