On 1 October 2025 the Government published its response to the December 2023 FHS consultation. The response confirmed the headline policy direction but introduced several technical changes that materially affected the final 24 March 2026 Approved Documents.
Solar PV mandate confirmed
The biggest single confirmation: solar PV becomes functionally mandatory at 40% of ground floor area. The Government rejected a lower 30% benchmark proposed by housebuilder lobby groups and a higher 60% proposed by sustainability NGOs.
Hydrogen-ready boilers excluded
The October 2025 response confirmed that "hydrogen-ready" boilers would not receive carbon credit under Part L 2026, ending a key area of housebuilder lobbying. Hybrid heat pump + gas systems were also excluded from the deemed-to-satisfy pathway.
HEM finalised as the compliance engine
The Home Energy Model (HEM) was confirmed as the new compliance methodology, fully replacing SAP for new dwellings after the transitional period. Existing dwelling SAP work for EPC continues unchanged.
Air permeability set at 3 (not 1)
Some Passive House lobby submissions argued for a tighter 1 m³/(h·m²) target. The Government settled at 3 — significantly tighter than the previous 8 maximum, but achievable without specialist Passive House detailing.
Implementation date confirmed
The 24 March 2027 commencement date was confirmed against industry calls for delay to 2028 or 2029. The 12-month transitional period was retained as a concession.