The Future Homes Standard — Complete Guide for UK New Builds

The Future Homes Standard (FHS) is the forthcoming update to Part L (Conservation of Fuel and Power) of the Building Regulations for England. It will require all new homes to produce 75–80% less carbon emissions than homes built to the 2013 standards, making them zero carbon ready — designed so they reach net zero as the electricity grid continues to decarbonise.

The FHS was first consulted on in October 2019, with a further consultation in 2023 setting out the detailed technical requirements. The government response to the 2023 consultation is expected in early 2026, with the regulations anticipated to come into force by late 2026. Compliance is demonstrated using the Home Energy Model (HEM) or SAP 10.3 during a transitional period.

Key Requirements at a Glance

The FHS introduces the most significant changes to new-build standards since Part L was last fundamentally updated. Here are the headline requirements:

75–80% Carbon Reduction

New homes must produce 75–80% less carbon emissions than homes built to the 2013 Part L baseline. This is a substantial step beyond the 2021 Part L uplift, which required a 31% reduction. The target is achieved through a combination of low-carbon heating, improved fabric performance, and on-site renewable generation.

Low-Carbon Heating

The FHS carbon targets are set at a level that fossil fuel heating cannot meet. In practice, this means:

• Air source heat pumps (ASHPs) or ground source heat pumps (GSHPs) will be the primary heating technology for the vast majority of new homes
• Heat networks with low-carbon sources are also acceptable
• Hybrid boilers and hydrogen-ready boilers will not comply with the standard
• Existing homes are not affected — gas boiler replacements remain legal in existing properties

Mandatory Solar PV

In June 2025, the government announced that solar panels will become a functional requirement of Building Regulations under the FHS. Developers must achieve 40% solar coverage of the building's floor area where feasible, or install a “reasonable amount” where shade or orientation constraints apply.

Combined with HEM's half-hourly modelling of solar generation and self-consumption, this requirement means new homes will both generate and intelligently use renewable electricity — reducing bills and grid demand.

Enhanced Fabric Performance

The FHS uses a whole-building performance approach through HEM, meaning builders can trade off between different fabric elements and systems. However, the notional dwelling specification (the reference building that sets the performance target) uses significantly improved fabric values compared to current standards. For full details, see our Part L Changes page.

The airtightness target of 3 m³/(h·m²) at 50 Pa is particularly significant — this is far tighter than the current regulatory maximum of 8 m³/(h·m²) and will typically require mechanical ventilation with heat recovery (MVHR) to maintain indoor air quality. See our Ventilation & Part F page for more detail.

Overheating Protection

Highly insulated, airtight homes can be prone to overheating in summer. The FHS works alongside Part O of the Building Regulations (introduced in June 2022), which sets requirements for controlling solar gains and providing adequate ventilation during warm weather. HEM's half-hourly simulation is particularly well-suited to modelling overheating risk, since it tracks internal temperatures throughout the year.

How Compliance Works

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. The notional building is a reference design with standardised specifications for fabric, heating, ventilation, and renewable energy.

During the transition period, two compliance routes are available:

• HEM: FHS assessment — the primary route, using the Home Energy Model with the FHS wrapper through the ECaaS platform
• SAP 10.3 — an updated version of SAP available as an interim option, allowing assessors to use familiar tools while the industry transitions to HEM

Both routes assess the same fundamental performance requirements, but HEM provides significantly more accurate modelling — particularly for heat pumps, solar PV, and battery storage. For a detailed comparison of the two compliance routes, see our Compliance Pathways page.

What Does “Zero Carbon Ready” Mean?

The government describes FHS homes as zero carbon ready. This does not mean they produce zero carbon emissions on day one. Instead, it means they are designed so that they will become net zero carbon as the electricity grid continues to decarbonise.

The logic is straightforward: a home heated by a heat pump and powered partly by solar PV will have progressively lower carbon emissions as the national grid shifts from fossil fuels to renewables. By the time the grid is fully decarbonised (the government's target is 2035 for clean power), a zero carbon ready home will produce zero operational carbon emissions without any further modifications.

This is why the FHS uses forward-looking carbon emission factors (averaging expected grid carbon intensity from 2025 to 2029) rather than the historical factors SAP relied on. HEM embeds these forward-looking factors in its calculation, automatically crediting the trajectory of grid decarbonisation.

Timeline and Current Status

The FHS has been in development since 2019 and has gone through multiple consultation rounds. The timeline has shifted several times, and as of early 2026 the programme appears to be running slightly behind its original schedule.

For live updates and detailed milestone tracking, see our Timeline & Status page.

Transitional Arrangements

The government has proposed a 12-month transitional period from the date the FHS regulations come into force. This gives the industry time to adapt, but the arrangements are stricter than previous regulatory uplifts:

• Plots registered before the FHS comes into force (expected late 2026) can begin construction under the current Part L 2021 rules up to 12 months later
• Plots registered after the FHS comes into force must comply with FHS immediately
• After the 12-month transitional period ends (expected late 2027), all new homes must comply with FHS regardless of when they were registered
• Transitional arrangements operate on an individual building basis, not site-wide — different homes on the same site may fall under different regulations
• “Commence” is defined to include drainage and foundation work, not just superstructure

These arrangements mean developers should expect a surge in plot registrations before the cut-off date. For detailed guidance on transitional strategies, see our Transitional Arrangements page.

Who Does the FHS Affect?

The Future Homes Standard affects everyone involved in building new homes in England. The impacts vary significantly by role:

SAP Assessors

Assessors face the most significant operational changes. HEM requires substantially more data than SAP — testing shows a standard house type takes approximately 1 hour 40 minutes in HEM versus around 20 minutes in SAP (excluding geometry and U-value calculations). New data points include detailed geometry, individual hot water outlet specifications, specific product data for all heating and ventilation equipment, and inverter specifications for PV systems. Missing data triggers punitive default values that are far more severe than in SAP.

Architects

Design decisions carry greater weight under HEM's more accurate modelling. Form factor becomes critical (compact thermal envelopes with a form factor below 3 are strongly favoured), orientation matters more due to half-hourly solar modelling, and thermal bridge-free detailing is increasingly important since thermal bridges are calculated at every timestep.

Developers

The additional build cost is estimated at 3–5% over current Part L compliance, driven primarily by heat pump installation, solar PV, enhanced insulation, and MVHR. However, FHS homes will have significantly lower running costs, making them more attractive to buyers. Developers must plan procurement carefully — heat pump and solar PV demand will spike as the deadline approaches.

Builders

On-site construction practices change substantially. Heat pump installation becomes standard, MVHR ducting must be integrated from the design stage, enhanced insulation means thicker wall builds and triple glazing, and airtightness requires meticulous construction detailing. The Building Safety Act also requires comprehensive digital records (the “Golden Thread”) for higher-risk buildings.

How FHS Relates to HEM

The Home Energy Model (HEM) is the calculation methodology that underpins FHS compliance. The relationship works as follows:

• HEM's core engine is a building physics simulation that models energy performance at half-hourly intervals
• The FHS wrapper sits on top of the core engine, adding the specific policy rules, notional building specifications, and compliance metrics required by the Future Homes Standard
• ECaaS (Energy Calculation as a Service) is the cloud API that delivers HEM to the industry, ensuring every assessment uses the identical calculation engine
• SAP 10.3 is available as an alternative compliance route during the transition, but HEM is the government's preferred long-term methodology

This modular approach means the FHS wrapper can be updated independently of the core physics engine, and future policy wrappers (such as the EPC wrapper currently under consultation) can be added without changing the underlying science. For more on how the calculation works, see SAP vs HEM.

FHS vs Part L 2021 — What Changes?

The 2021 Part L uplift (which came into force in June 2022) was described as an interim step towards the Future Homes Standard. It required a 31% reduction in carbon emissions. The FHS takes this significantly further:

For a detailed breakdown of every Part L change, see our Part L Changes page.

Frequently Asked Questions

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