What is the Future Homes Standard?
The Future Homes Standard (FHS) is the UK Government's policy to ensure every new home in England is "zero carbon ready" — designed so that, as the electricity grid decarbonises, no further retrofit work will ever be needed. It is delivered through the 75% CO₂ reduction target written into Part L 2026 of the Building Regulations (versus the 2013 baseline), and through the parallel Approved Document F (ventilation). SAP 10.3 is the compliance methodology at launch; the Home Energy Model (HEM) — whose launch was postponed in June 2026 — will dual-run with SAP for at least 24 months once approved.
The Government published the final Approved Documents on 24 March 2026 following the December 2023 consultation. They come into force on 24 March 2027, with transitional protection to 24 March 2028 — but only for buildings whose building notice, initial notice or full-plans application is with building control before 24 March 2027 AND which commence on site before 24 March 2028 (assessed per building). Higher-Risk Buildings (HRB) provisions follow six months later on 24 September 2027.
For the new-build solar PV market specifically, three FHS changes matter most:
- Solar PV becomes functionally mandatory. Requirement L3 (new) demands renewable electricity generation equivalent to 40% of the dwelling's ground floor area. Token systems no longer pass Building Control.
- Fossil-fuel heating is effectively banned. The carbon targets cannot be hit with gas, oil, LPG or "hydrogen-ready" boilers. Air source heat pumps dominate new-build heating from 2027 onward.
- Ventilation and airtightness tighten — fabric largely does not. The notional dwelling's air permeability tightens from 5.0 to 4.0 m³/(h·m²) with continuous mechanical extract ventilation (dMEV), while wall, roof, floor and door U-values are unchanged from Part L 2021. The FHS step-change is heating and PV, not fabric.
The six core FHS requirements
Each of these requirements is functional, not prescriptive — meaning Building Control needs to see the outcome (CO₂, U-values, kWh) rather than a particular product. In practice though, the FHS Impact Assessment expects the great majority of dwellings to use the same broad specification.
Mandatory on-site renewable electricity generation
Requirement L3 (new) makes solar PV functionally mandatory. Coverage must equal at least 40% of the dwelling's ground floor area where geometrically feasible. Where 40% is unachievable due to shading, orientation or roof geometry, a "reasonable amount" must be installed and documented in the SAP/HEM file.
Low-carbon heating only — gas boilers effectively banned
There is no explicit boiler ban, but the carbon targets (0.086 kgCO₂/kWh electricity carbon factor, 1.969 primary energy factor) are set at a level fossil fuel heating cannot achieve. Hybrid heat pumps and "hydrogen-ready" boilers do not comply. Air source heat pumps, ground source heat pumps and connection to heat networks are the viable options.
Fabric performance: largely unchanged — the step-change is elsewhere
The SAP 10.3 notional dwelling keeps wall 0.18, roof 0.11, floor 0.13 and door 1.0 W/m²K unchanged from Part L 2021; air permeability tightens modestly from 5.0 to 4.0 m³/(h·m²). Limiting (backstop) values in ADL1 2026 Table 3.1 are also unchanged (wall 0.26, air 8.0). The real FHS step-change is heating, PV and ventilation — not fabric.
Continuous mechanical ventilation (dMEV in the notional dwelling)
The SAP 10.3 notional dwelling specifies decentralised mechanical extract ventilation (dMEV), not MVHR. MVHR remains a common designer choice on airtight designs, but it is not what the notional model assumes.
Overheating protection (Part O continues)
TM59 modelling for residential dwellings remains required. Solar shading, smaller windows on west elevations and night-cooling strategies are commonly needed alongside the larger PV array.
Zero Carbon Ready outcome
Homes are designed so that, as the electricity grid decarbonises, no further work is needed. Compliance uses "forward-looking carbon emission factors" averaging grid carbon intensity 2025–2029.
Who the FHS affects
The FHS applies only to new dwellings — existing homes are unaffected and gas boiler replacements in existing properties remain legal. But within new-build, the impact is universal and varies by player:
Volume housebuilders
Must redesign standard house types for Part L 2026 — early adopters already retooling 2026 phases of existing developments.
SME developers
Higher per-plot cost (~£4,350) tightens margins. Procurement of compliant solar+ASHP packages becomes a critical supply-chain decision.
Self-builders & custom-build clients
Transitional protection applies only if a building notice, initial notice or full-plans application is submitted to building control before 24 March 2027 AND work commences on site before 24 March 2028 (assessed per building). Plots outside that window must comply in full.
Housing associations
The £39bn Social and Affordable Homes Programme (SAHP) 2026–2036 (bidding opened February 2026) already requires FHS-equivalent specs. Most RSLs are ahead of the curve.
Modular & MMC manufacturers
Factory-fitted in-roof PV and pre-insulated panels position MMC favourably for FHS economics.
Architects & SAP assessors
SAP 10.3 is the sole compliance methodology at FHS launch (the Home Energy Model launch was postponed in June 2026; once approved, HEM will dual-run for at least 24 months). Assessor demand for SAP 10.3 re-accreditation is the near-term pinch point.
What the FHS costs per home
The Government's own Impact Assessment estimates an additional build cost of approximately £4,350 per dwelling per dwelling (weighted average, 2025 prices). This covers the PV array, air source heat pump, enhanced insulation, MVHR and improved windows and doors. The Impact Assessment's per-type estimates: mid-terrace £5,690, semi-detached £5,600, detached £5,160, low-rise flats £5,300, mid-rise flats £2,210, high-rise £1,550 — note a detached home is actually cheaper than a semi to make compliant, because the larger roof makes the PV requirement easier to meet.
From the homeowner's perspective the premium pays back fast. Sunsave's analysis of 150+ UK solar-plus-battery systems found an average electricity bill reduction of 86%; at 2026 tariffs the FHS premium typically pays back in around 7 years for in-roof PV fitted at build stage (a retrofit equivalent runs 9–10 years), before any property-value uplift is counted.
Exemptions and flexibilities
The PV requirement is functional, not absolute. Where the 40% ground-floor-area target is not geometrically achievable the developer must install a "reasonable amount" and document the technical justification in the SAP/HEM compliance file. In practice exemptions are narrow:
- Heavily shaded plots where rooftop PV would generate <50% of typical output
- Higher-Risk Buildings (HRB, over 18m) are NOT exempt — their provisions commence later (24 September 2027), and multi-dwelling buildings apportion PV via ADL1 2026 equations 5.2/5.3 and the "reasonably practicable roof area" route (para 5.74)
- Roof geometry which cannot physically accommodate PV (e.g. mansards on conservation-area infill)
- Listed building consent overrides (rare for new builds, mostly applies to listed-curtilage plots)
Fabric performance — what actually changes (and what doesn't)
A common misreading of the FHS is that it radically tightens the building fabric. It doesn't: the SAP 10.3 notional dwelling keeps almost every fabric value unchanged from Part L 2021 — the step-change sits in heating, PV and ventilation. Limiting (backstop) values in ADL1 2026 Table 3.1 are also unchanged (e.g. wall 0.26 W/m²K, air permeability 8.0 m³/(h·m²)):
| Element | Part L 2021 notional | FHS 2026 notional (SAP 10.3) | Change |
|---|---|---|---|
| External wall | 0.18 W/m²K (unchanged) | 0.18 W/m²K | unchanged |
| Ground floor | 0.13 W/m²K (unchanged) | 0.13 W/m²K | unchanged |
| Roof | 0.11 W/m²K (unchanged since 2021) | 0.11 W/m²K | unchanged since 2021 |
| External door | 1.0 W/m²K (unchanged since 2013) | 1.0 W/m²K | unchanged since 2013 |
| Air permeability | 5.0 m³/(h·m²) @ 50 Pa (Part L 2021 notional) | 4.0 m³/(h·m²) @ 50 Pa (notional) | tightened (5.0 → 4.0) |
SAP 10.3 now, the Home Energy Model later
The Home Energy Model is a half-hourly dynamic simulation designed to eventually replace SAP, modelling PV generation, battery storage and self-consumption realistically across the year. Its launch was postponed in June 2026 — so FHS compliance begins on SAP 10.3, with HEM to dual-run for at least 24 months once approved.
Practical impact for designers: SAP 10.3 is the sole approved compliance methodology at FHS launch — the Home Energy Model's launch was postponed in June 2026 to ensure robustness. Once HEM is approved it will run in parallel with SAP for a minimum of 24 months before becoming the sole route. Early industry estimates suggested HEM assessments take several times longer than legacy SAP, so assessor capacity is worth securing early either way.
Scotland, Wales and Northern Ireland
Scotland: Section 6 (Energy) of the Scottish Building Standards is following a parallel timeline. Scotland's "New Build Heat Standard" already prohibits direct-emission heating systems in buildings commencing warrant from 1 April 2024 — Scotland is two years ahead of England on heating decarbonisation.
Wales: Welsh Part L follows the England/Wales framework but Welsh Government has historically tightened thresholds further. A 2026 Welsh Building Regulations consultation is expected to mirror or exceed the FHS PV coverage requirement.
Northern Ireland: Building Regulations (Northern Ireland) Technical Booklet F2 has not yet adopted FHS-equivalent provisions; consultation expected 2026–27.
What to do now
If you are a developer or housebuilder: redesign your standard house types now. Allowable transitional grace ends at March 2028 but every plot reserved for sale from spring 2026 onwards is realistically being marketed as FHS-compliant already. See the developer hub for the compliance checklist, per-plot pricing model and SAP/HEM modelling service.
If you are a self-builder or custom-build client: any project where you apply for Building Control (or full plans / building notice) on or after 24 March 2027 must comply. If you are nearing the start-on-site decision in 2026, talk to us about whether to design to FHS now or hold to the transitional rules. See the self-builder hub.