Future Homes Standard 2026: what it means for timber build

The Future Homes Standard 2026 is the largest change to building energy rules in England for a decade. The new Approved Documents L and F were published on 24 March 2026, and Approved Document L2 followed on 27 March 2026. Part L 2021 remains the law until the new standard comes into force.

For anyone specifying an imported timber kit, the question is which rulebook the project falls under. The fabric and heating decisions that satisfy it are taken at concept stage, not at building control.

Future Homes Standard 2026: dates and transitional arrangements

• 24 March 2026: the standard published, with new Approved Documents L and F
• 27 March 2026: Approved Document L2 published
• 24 March 2027: in force for new dwellings
• 24 September 2027: in force for higher-risk buildings
• 24 March 2028: the transitional cut-off for work begun under the previous rules

Until 24 March 2027 you design to Part L 2021. After that the new Approved Documents apply, and the Future Homes Standard transitional arrangements decide the borderline projects. The date the application goes in matters more than the date you break ground.

What the standard actually requires

• Roughly a 75–80% cut in CO2 against the 2013 baseline
• Gas boilers are non-compliant; heating comes from heat pumps or heat networks
• Solar PV at roughly 40% of the ground-floor area
• Airtightness around 4 m³/h·m² at 50 Pa
• SAP 10.3 as the assessment method at launch, with the Home Energy Model dual-running later

The list is short, but it reorders the design process. Heating plant, roof orientation and the airtightness strategy are locked in at the beginning of a project, and all of them are expensive to revisit once a kit is in production.

Why the airtightness target favours factory-built timber

Around 4 m³/h·m² at 50 Pa is a different order of workmanship from the traditional norm. It is won at junctions — wall to floor, wall to roof, and every service penetration — and junctions are exactly what a factory does better than a cold, wet site. Closed-panel timber systems are jigged, taped and inspected indoors, then craned into place in days.

That is why prefabricated timber tends to close the performance gap between the modelled figure and the tested one. The air test at completion is far easier to pass when the airtight layer went in under cover.

Fabric first, then plant

The standard is met most cheaply by cutting demand before sizing the heat pump. Every watt the fabric does not lose is a watt the plant never has to supply, and a smaller unit is cheaper and easier to site. A timber frame carries deep insulated build-ups without disproportionate wall thickness, and the frame members conduct far less heat than steel.

Embodied carbon is not regulated through Part L, but it is increasingly asked for in planning and in voluntary assessment schemes. It is the measure on which timber has the clearest margin.

Solid timber and log walls under Approved Document L

Approved Document L sets limiting values element by element, not material by material. A solid log wall is judged against the same wall standard as any other construction. In practice that points towards an insulated build-up or a heavier section in the heated envelope of a detached house, while solid timber comes into its own in outbuildings and sauna cabins where the fabric standard is not the same.

Zero emission building definition: the EU picture

EU buyers work to a different instrument. The recast EPBD, Directive (EU) 2024/1275, introduces the zero emission building definition and requires new public buildings to meet it from 1 January 2028 and all new buildings from 1 January 2030. Zero emission buildings under the EPBD matter to Irish and other EU clients; they do not apply in Great Britain, where the Future Homes Standard is the operative rule.

If you build on both sides of the Irish Sea, run two specifications rather than assuming the tighter one covers both. The metrics and the dates are not the same.

How to prepare now

• Fix the heating strategy first: heat pump or heat network, never a gas boiler
• Design the roof for solar PV at roughly 40% of the ground-floor area, even if the panels come later
• Write the airtightness target into the supply contract, and state who owns the test result
• Ask the kit supplier for the U-values, junction detailing and air permeability assumed in the calculation
• Check your application date against the transitional cut-off of 24 March 2028

The direction is fixed and the dates are published. A project completing close to 2027 should be designed to the new standard now, and specified by strength class and moisture content, because retrofitting plant, roof structure and junction detailing costs far more than building them in.

• Future Homes and Buildings Standard published 24 March 2026; Approved Document L2 on 27 March 2026.
• In force 24 March 2027 for new dwellings and 24 September 2027 for higher-risk buildings.
• Transitional cut-off is 24 March 2028; Part L 2021 remains the law until the changeover.
• Around 75–80% less CO2 than 2013, no gas boilers, solar PV at about 40% of ground-floor area.
• Airtightness near 4 m³/h·m² at 50 Pa, assessed in SAP 10.3 with the Home Energy Model later.
• The EPBD zero emission building rules (2028 and 2030) bind EU and Irish projects, not Great Britain.