The Future Homes Standard (FHS) will require all new homes in England to produce at least 75% less carbon emissions than homes built to the 2013 standards. For housing developers, this means heat pumps instead of gas boilers, mandatory solar PV, enhanced insulation, mechanical ventilation, and a new compliance methodology through the Home Energy Model (HEM). The FHS Impact Assessment estimates an additional build cost of approximately £4,350 per dwelling (weighted average, 2025 prices), and FHS homes will have significantly lower running costs than existing homes, making them more attractive to buyers.
This page summarises the key impacts for developers. For detailed cost analysis, transitional strategy, and procurement guidance, see our Developer Compliance & Cost Guide.
Cost Impact Overview
The additional build cost is driven by several mandatory changes to how homes are built. The table below breaks down the main cost drivers and their estimated impact:
| Cost Driver | Part L 2021 (Current) | Future Homes Standard |
|---|---|---|
| Heating system | Gas boiler (~£1,500–2,500) | Air source heat pump (~£5,000–8,000) + hot water cylinder |
| Solar PV | Not required | Mandatory (~£4,000–6,000 for typical 3-bed) |
| Ventilation | MEV or trickle vents (~£300–500) | dMEV (or MVHR) system (~£3,000–5,000 installed) |
| Windows | Double glazing (1.4–1.6 W/m²K) | High-performance windows (~1.2 W/m²K, typically triple glazed), ~£1,500–3,000 premium |
| Insulation | Standard Part L 2021 spec | Enhanced fabric (~£1,000–2,000 additional) |
| Airtightness | Standard construction detailing | Enhanced detailing + testing (~£500–1,500 additional) |
These figures are indicative and will vary significantly by house type, volume, and supply chain. Larger developers with established supply chains will typically achieve lower per-unit costs. The cost premium is also expected to reduce as the market scales up heat pump production and solar PV installation becomes routine.
Transitional Arrangements
The government has confirmed a 12-month transitional period from when the FHS comes into force. Understanding these arrangements is critical for planning your pipeline:
- Projects with applications submitted before 24 March 2027 can build to Part L 2021 if commenced before 24 March 2028
- Projects submitted on or after 24 March 2027 must comply with FHS immediately
- After 24 March 2028, all new homes must comply regardless of registration date
- Transitional arrangements operate on an individual building basis, not site-wide. Different plots on the same site may fall under different regulations
- “Commence” is defined to include drainage and foundation work, not just superstructure
Key Dates for Developers
| Milestone | Date | What It Means for Developers |
|---|---|---|
| Approved Documents published | 24 March 2026 | Final regulations, fabric specs, and transitional arrangements confirmed |
| FHS comes into force | 24 March 2027 | Application deadline for transitional eligibility |
| Transitional period | 24 Mar 2027 – 24 Mar 2028 | 12-month window to commence Part L 2021 projects |
| Transitional period ends | 24 March 2028 | All new homes must comply with FHS, no exceptions |
These dates are now confirmed following the publication of the Approved Documents on 24 March 2026. See our Timeline & Status page for live updates.
Compliance Methodology
FHS compliance is demonstrated by showing that a proposed dwelling performs at least as well as a notional building of the same size and shape. During the transitional period, two routes are available:
- HEM via ECaaS: The primary route, using the Home Energy Model's half-hourly dynamic simulation through the centralised ECaaS platform
- SAP 10.3: The calculation methodology available at FHS launch. HEM will be approved later, followed by a dual running period of at least 24 months
HEM requires substantially more detailed input data than SAP and runs calculations in under 2 seconds via ECaaS, though the more detailed data entry requirements mean overall assessment time is longer. It provides more accurate modelling of modern technologies, particularly heat pumps and solar PV. For a full comparison, see our Compliance Pathways page.
Frequently Asked Questions
How much more will FHS homes cost to build?
The FHS Impact Assessment estimates an additional build cost of approximately £4,350 per dwelling (weighted average, 2025 prices) over current Part L 2021 compliance. The main drivers are heat pump installation, mandatory solar PV, enhanced insulation (high-performance glazing), dMEV or MVHR, and improved airtightness. Compared to a typical existing home, annual energy costs will be significantly lower. Compared to a Part L 2021 new build, the difference may be marginal because heat pumps use electricity, which costs approximately four times more per unit than gas.
What is the FHS plot registration deadline?
Projects with applications submitted before 24 March 2027 can build to Part L 2021 if commenced before 24 March 2028. After that, all new homes must meet FHS. Arrangements operate on an individual building basis, not site-wide. Older transitional provisions (2013 and 2021) have been revoked. See our Transitional Arrangements page for details.
Can developers still install gas boilers under the FHS?
No. The FHS carbon targets are set at a level that gas boilers cannot meet. New homes will need low-carbon heating, primarily heat pumps. Heat networks with low-carbon sources are also acceptable. Hybrid and hydrogen-ready boilers will not comply. During the transitional period, plots commenced under Part L 2021 can still use gas boilers.
What counts as 'commencing' construction for transitional purposes?
“Commence” is defined to include drainage and foundation work, not just superstructure construction. This is broader than some previous regulatory uplifts. To benefit from the transitional period, a plot must have commenced (including drainage and foundations) within the 12-month window after the FHS comes into force.
How much will FHS homes save on energy bills?
Compared to a typical existing home, annual energy costs in an FHS home will be significantly lower. Compared to a Part L 2021 new build, the difference may be marginal because heat pumps use electricity, which costs approximately four times more per unit than gas. The low running costs come from heat pump efficiency (2.5–4 units of heat per unit of electricity), mandatory solar PV, enhanced insulation, and mechanical ventilation (recovering a minimum of 73% of exhaust air heat per AD L1, with high-performance units achieving 85–95%). As the grid decarbonises, these homes will also become progressively lower-carbon.
Related Pages
Developer Compliance & Cost Guide
Detailed cost analysis, transitional strategy, risk management, and procurement advice.
Transitional Arrangements
Plot registration deadlines, commencement definitions, and strategies for the transition period.
For Builders
What changes on site under the Future Homes Standard: heat pumps, mechanical ventilation, airtightness.
For Architects
How HEM changes design decisions for form factor, orientation, and glazing.