The Future Homes Standard Explained for Developers

Every few years, the government moves the goalposts on building energy standards. You update your specs, brief your supply chain, and get comfortable. Then they move them again.

This time, however, the move is different in scale. The Future Homes Standard (FHS), confirmed in March 2026 and coming into force in March 2027, is not a modest tightening of existing rules. Gas boilers are effectively gone from new builds. Solar PV is now a legal requirement. And the carbon reduction target has shifted from 30% better than 2013 to 75% better than 2013.

If you are responsible for delivering new residential developments, this guide is for you. It covers what the FHS is, where it came from, how SAP scores work, which technologies actually help you hit compliance, and what the smartest developers are doing right now to stay ahead.

By the end of it, you should be able to walk into any FHS conversation, be it with a design team, a planning authority, or your board, and know exactly what is being asked of you and why.

What Is the Future Homes Standard?

The Future Homes Standard is an update to Part L (Conservation of Fuel and Power) of the Building Regulations for England. Published on 24 March 2026, it sets new mandatory requirements for the energy performance of all new-build homes. It comes into force on 24 March 2027 – less than a year from now.

In plain terms, it means this: every new home built in England from 2027 onwards must be ‘zero carbon ready’. The home should not need any major energy upgrades in the future to become a net zero carbon building. It achieves this by generating less carbon from day one and by being set up to benefit automatically as the UK electricity grid continues to decarbonise.

Three things define what the FHS demands in practice:

• Low-carbon heating: almost universally a heat pump (air source or ground source)
• Solar PV: now a legal requirement for most new dwellings
• Improved building fabric: tighter, better-insulated homes that waste less heat

A 75% reduction in carbon emissions compared to homes built under 2013 standards. Gas boilers cannot come close to meeting it.

The regulations were laid before Parliament on 24 March 2026, with a 12-month transition period running until 24 March 2028. Projects with building control applications submitted before 24 March 2027 can still build to Part L 2021 standards, provided construction commences before 24 March 2028. After that point, the FHS applies to all new homes, no exceptions.

It is worth noting that the FHS applies to England only. Wales and Scotland operate their own separate regulatory frameworks with different timelines.

The History of Part L

Understanding the FHS is easier if you understand the journey that led to it. These tightening regulations did not appear from nowhere.

Part L 2013: The Starting Point

The 2013 version of Approved Document Part L was the baseline for new-build energy performance for almost a decade. Gas boilers were the standard. Insulation was improving but not dramatically. The EPC system was in place, but homes routinely achieved a B or C rating without much effort. Carbon was not the primary focus, energy efficiency was, and the two are not always the same thing.

The 2019 Consultation: The Beginning of the End for Gas

In October 2019, the government launched its first Future Homes Standard consultation. This was the opening shot of a new direction. The key proposal: new homes would need to produce significantly lower carbon emissions, and eventually fossil fuel heating would not be permissible at all. The construction industry responded with a mix of enthusiasm, concern, and a reasonable amount of confusion.

Part L 2021: The Interim Step

The government knew a step-change to full FHS standards was not possible overnight. So in December 2021, and coming into force June 2022, it introduced an interim uplift to Parts L and F of the Building Regulations. This required new homes to achieve roughly 30% less carbon than the 2013 baseline.

Gas boilers were still permitted, but only when offset by other measures, typically solar PV. Insulation targets tightened. Airtightness improved. It was a meaningful step, but the industry knew it was a stepping stone, not the destination.

The 2023 Technical Consultation and Final Confirmation

In December 2023, the government published its detailed technical consultation on the full FHS, alongside the first version of the Home Energy Model (HEM), which is the replacement for the SAP calculation system. After extensive industry feedback, the final Approved Documents were published on 24 March 2026.

How Standards Have Changed:

Requirement	Part L 2013	Part L 2021	FHS 2026
Carbon reduction vs 2013 baseline	Baseline	~30% less	~75% less
Primary heating	Gas boiler (standard)	Gas still permitted	Heat pump (mandatory in practice)
Solar PV	Not required	Sometimes needed	Mandatory (40% of ground floor area)
Airtightness target	10 m³/hr/m²	~5 m³/hr/m²	~4 m³/hr/m²
Ventilation notional	Natural/local extracts	Natural/local extracts	Decentralised MEV (dMEV)
Compliance tool	SAP 2012	SAP 10.2	SAP 10.3 / Home Energy Model
EPC rating achievable	B-C typical	B typical	A typical

Each iteration of the Future Homes Standard has moved in one direction; less carbon, less fossil fuel, more renewables.

What Exactly Does the FHS Require?

Here is the practical breakdown of what the Future Homes Standard demands of every new residential development.

1. Low-Carbon Heating

The FHS does not use the words ‘heat pumps are mandatory’. It does not need to. Its carbon targets (75% below the 2013 baseline) are set at a level that gas boilers simply cannot reach. The notional building in SAP 10.3 (the compliance calculation tool) is modelled around an air source heat pump. That is the benchmark everything else is measured against.

In practice, the heating options that comply are:

• Air source heat pumps (ASHP), which are the most common solution for most new builds
• Ground source heat pumps (GSHP), higher efficiency, better suited to larger plots or where ground conditions allow
• Heat networks; communal or district heating systems using a low-carbon source

Hybrid boilers, hydrogen-ready boilers, and conventional gas boilers will not meet the standard. This is effectively the end of gas in new residential development.

2. Solar PV Now Mandatory

Under new Requirement L3, added to the Building Regulations through the March 2026 amendments, on-site renewable electricity generation is a legal functional requirement for the first time. In almost all cases, this means solar photovoltaic panels.

The required system size is equivalent to 40% of the dwelling’s ground floor area. For a typical three-bedroom house with a ground floor area of 60m², that equates to approximately a 2.4 kWp system as a rough starting point, though your SAP assessor will calculate the precise specification based on your actual designs.

Exemptions applywhere solar is not feasible, for instance, in buildings over 18 metres tall, or where site conditions mean a 720 kWh/year output target cannot be reached. The regulations include a ‘reasonable amount’ provision for constrained sites, but the burden is on the developer to demonstrate why the full requirement cannot be met.

3. Tighter Airtightness

Fabric standards remain broadly aligned with Part L 2021 in terms of minimum U-values (how well your walls, floors, and roof resist heat loss). However, the airtightness benchmark in the notional building has tightened from 5 m³/hr/m² to 4 m³/hr/m². In plain terms, your buildings need to be measurably less draughty.

Airtightness is tested on-site at completion, and the result feeds into the SAP calculation. This target is measured, evidenced, and signed off by building control.

4. Updated Ventilation Requirements

The notional dwelling in FHS is now modelled with decentralised mechanical extract ventilation (dMEV). This replaces natural ventilation with local extracts as the baseline assumption. The practical implication: mechanical ventilation should be designed in from the start.

Waste water heat recovery (WWHR) systems, which capture heat from shower and bath drainage before it disappears down the drain, are included in the notional benchmark for the first time. They are not mandatory, but they are now part of the standard reference point, and they can make a real difference to compliance on challenging plots.

5. How Compliance Is Demonstrated

Compliance is assessed using two metrics compared to a notional (reference) building of the same size and shape:

• Dwelling Emission Rate (DER) vs Target Emission Rate (TER)
• Dwelling Fabric Energy Efficiency (DFEE) vs Target Fabric Energy Efficiency (TFEE)
• Dwelling Primary Energy Rate (DPER)

All three must pass. Meeting one or two out of three is not enough.

The calculation tool for FHS compliance is SAP 10.3, the updated version of the Standard Assessment Procedure, which will run during the transitional period. The longer-term plan was to replace SAP entirely with the new Home Energy Model (HEM), but HEM has been delayed and its timeline is currently uncertain. SAP 10.3 remains the required route for now.

SAP Scores Explained

If you have been involved in new-build delivery for any length of time, you have come across SAP calculations. You may have nodded along politely while your energy assessor talked about DER and TER and wondered what any of it actually means. Here is the plain version.

What Is SAP?

SAP stands for Standard Assessment Procedure. It is the UK government’s official method for assessing the energy performance of new homes. Every new build needs it. Without an approved SAP calculation and a final Energy Performance Certificate (EPC), building control cannot sign the project off.

SAP produces a rating between 1 and 100 (and sometimes above 100, when the home generates more energy than it uses). The higher the number, the more energy-efficient the home:

• Below 39: G rating (very poor)
• 39–54: F rating
• 55–68: E rating
• 69–80: D rating
• 81–91: C rating
• 92 or above: A or B rating (excellent)

FHS-compliant homes, with heat pumps and solar PV, typically achieve an A rating. Gas-heated homes rarely exceeded a B.

How Is SAP Calculated?

SAP creates a digital model of the proposed home. It factors in the building’s geometry, insulation levels, air permeability, heating system efficiency, ventilation, and any on-site energy generation such as solar PV. It then compares the proposed design against a notional (reference) building of the same size and orientation.

The assessment runs twice. First, at design stage to check the proposed specification will meet the regulations before anything is built. Second, at completion, using as-built information (the actual heat pump model installed, the airtightness test result, the PV system commissioned). Both must pass.

What Does SAP 10.3 Change?

The move from SAP 10.2 (used under Part L 2021) to SAP 10.3 under the FHS brings several important changes:

• The carbon and energy factors for gas have been revised upward, making it harder to achieve compliance with fossil fuel systems
• Heat pump performance is modelled using a Coefficient of Performance (COP) of 2.5 across all dwellings, reflecting real-world rather than idealised performance
• The notional building now assumes dMEV ventilation and includes waste water heat recovery
• The solar PV requirement is baked into the notional, making it part of the compliance baseline

The Home Energy Model (HEM) was intended to replace SAP entirely, offering far more detailed half-hourly modelling of solar generation, battery storage, and heat pump performance. It has been delayed. SAP 10.3 remains the compliance route for now, with HEM expected to follow, but without a confirmed date.

Which Renewable Technologies Support FHS Compliance?

Meeting the FHS is about using different systems work together to hit the carbon, energy, and fabric targets simultaneously. Here is a guide to the technologies that matter and what each one actually contributes.

Technology	Typical SAP impact	FHS compliance contribution	Key consideration
Air source heat pump	High positive	Primary heating requirement	Correct sizing and spec important
Ground source heat pump	Very high positive	Primary heating, higher efficiency	Higher upfront cost, best for larger plots
Solar PV (rooftop)	Significant positive	Mandatory (40% of ground floor area)	Orientation affects output
Battery storage	Moderate positive	Not mandatory but improves self-consumption	Often required to hit carbon targets
Waste water heat recovery	Moderate positive	Included in notional benchmark	Simple, cost-effective addition
Mechanical ventilation with heat recovery (MVHR)	Positive	Complements airtightness	Requires correct commissioning
Decentralised MEV (dMEV)	Positive	New notional ventilation standard	Lower cost than full MVHR
High-performance glazing (triple glazing)	Moderate positive	Reduces heat loss, supports TFEE	Balance against overheating risk
Enhanced wall/floor/roof insulation	High positive	Reduces DFEE, supports all targets	Foundation of fabric-first approach

Air Source Heat Pumps

An air source heat pump (ASHP) extracts heat from outdoor air and uses it to heat the home and hot water. Modern ASHPs work efficiently even in cold weather (up to -15 degrees), and because they run on electricity rather than gas, their carbon footprint falls as the grid decarbonises over time.

For FHS compliance, an ASHP is the most practical solution for the vast majority of new-build plots. They require no groundworks (unlike ground source), can be installed on relatively small sites, and fit neatly into a fabric-first design approach. Getting the sizing right matters, an undersized unit with small radiators will not perform efficiently and may struggle in colder weather.

Typical SAP impact: Significant. An ASHP alone will move a well-insulated home from a C or D (gas) to a B or A rating.

Ground Source Heat Pumps

Ground source heat pumps (GSHP) extract heat from the ground rather than the air, via buried pipework (either horizontal arrays or vertical boreholes). The ground maintains a more stable temperature than air year-round, which means GSHPs typically achieve a higher COP than ASHPs — meaning more heat for every unit of electricity consumed.

The trade-off is cost and complexity. Boreholes require specialist drilling, and horizontal arrays need sufficient land area. GSHPs are best suited to larger plots, rural developments, or schemes where ground conditions make them viable. On denser urban sites, an ASHP is usually the more practical answer.

Typical SAP impact: Very high. GSHPs often achieve the best DER figures of any heating system, and can sometimes reduce the PV requirement by improving the carbon position.

Solar PV

Solar photovoltaic panels convert sunlight into electricity. Under the FHS, they are now a mandatory requirement, as an array equivalent to 40% of the dwelling’s ground floor area must be installed on most new homes. This is a step-change from the previous position, where solar was used as a lever to compensate for less efficient heating systems.

South-facing roofs generate the most electricity, but east/west-facing arrays are permitted, and in some site layouts are unavoidable. SAP 10.3 models the energy output based on orientation and pitch, so your assessor can calculate the compliance impact of any given roof arrangement.

Typical SAP impact: Significant. On a heat pump-heated home, a correctly sized PV array often pushes the rating from A into an A+ territory, and can push the DER below the TER by a comfortable margin.

Battery Storage

Battery storage is not mandatory under the FHS, but it is increasingly becoming a practical necessity on sites where hitting the carbon targets without it proves difficult. A battery stores the electricity generated by solar PV during the day for use in the evening, improving self-consumption and reducing reliance on grid electricity.

The Home Energy Model, when it arrives, will model battery performance more accurately than SAP 10.3. For now, battery storage can improve the SAP position where the modelling supports it. It also improves the commercial proposition for homebuyers, who benefit from much lower running costs, even without solar PV.

Waste Water Heat Recovery

Waste water heat recovery (WWHR) systems capture heat from shower waste water and use it to pre-heat the incoming cold water supply. On a dual-shower installation, the efficiency improvement can be meaningful.

WWHR is now included in the FHS notional building for the first time, which means it is part of the reference benchmark. Installing it can therefore help bridge any gap between your proposed design and the notional. It is relatively inexpensive, simple to install during the build, and adds no operational complexity for residents.

Mechanical Ventilation with Heat Recovery (MVHR)

MVHR systems extract stale air from the home while simultaneously recovering the heat from it to warm incoming fresh air. In a very airtight home, which an FHS property should be, MVHR provides excellent ventilation without the heat loss that natural ventilation would create.

The notional dwelling under FHS uses dMEV rather than full MVHR, so MVHR is not the compliance default. However, on very airtight, well-insulated homes, it can improve the DFEE calculation and provide a better-performing home for residents. It requires careful commissioning to work correctly, as a poorly commissioned MVHR system can create noise and poor air quality.

Enhanced Fabric: The Foundation of Everything

Every technology in the list above works better in a well-insulated, airtight building. The principle of ‘fabric first’ (designing the building envelope to minimise heat loss before adding mechanical systems) remains the cornerstone of good FHS design.

The key fabric elements:

• Wall U-values: The FHS notional uses 0.18 W/m²K as a benchmark. Better-insulated walls mean lower heat demand and a smaller heat pump.
• Floor U-values: Typically 0.13 W/m²K in the notional. Good floor insulation matters more than many developers realise.
• Roof U-values: Typically 0.11 W/m²K in the notional.
• Windows and doors: The notional uses 1.2 W/m²K for windows. Triple glazing can improve on this, though overheating risk must be managed.
• Airtightness: Targeting 3–4 m³/hr/m² rather than the 5 m³/hr/m² limit gives headroom in the SAP calculation.
• Thermal bridging: Heat escaping through junctions and edges can be a significant source of loss if not properly detailed. Accredited Construction Details (ACDs) provide a reliable route to managing this.

The single most effective thing you can do before choosing a heating system is make the building envelope as good as it can practically be. A smaller heat pump on a well-insulated home beats a larger one on a leaky one.

The Key Dates and Transition Arrangements

For any project currently in planning, design, or pre-commencement, the transition arrangements are very important. Here is how they work.

• 24 March 2026:
  • Government publishes the final FHS Approved Documents. This is the confirmed specification that developers and designers should now be working to.
• 24 March 2027:
  • FHS regulations come into force for all new non-higher-risk buildings. From this date, all new building control applications must demonstrate FHS compliance.
• 24 March 2028:
  • The 12-month transitional period ends. Projects with applications submitted before March 2027 must have commenced construction by this date to remain under Part L 2021. After this point, every new home must comply with FHS regardless.
• 24 September 2027:
  • FHS regulations apply to higher-risk buildings (those 18 metres or taller), with a separate transitional period reflecting the longer timescales involved in these developments.

One important change to how ‘commencement’ is defined:

Under previous regulations, laying foundations was often sufficient to be considered commenced. Under the new rules, commencement requires completion of the ground floor slab. This matters for projects trying to lock in transitional protection, and you’ll need to check with your legal and building control teams before assuming existing groundworks are sufficient.

The government has also revoked older transitional provisions from 2013 and 2021 that still allowed some sites to build to 2010 energy standards. Any un-commenced plots relying on those legacy provisions must now meet the FHS. If you have a stalled site that was relying on old transitional arrangements, the clock has started.

What This Means for Your Costs

The obvious question. The government’s own impact assessment estimates that FHS-compliant homes will cost more to build than a Part L 2021 home, primarily due to the heat pump and solar PV requirements.

However, the picture on running costs is more nuanced than it might first appear.

FHS homes will not pay a gas standing charge, which currently costs households in the region of £100–130 per year regardless of usage. Heat pump efficiency means energy consumption is lower than a gas-heated equivalent for the same warmth. The government estimates FHS homes could save residents up to £830 per year compared to a standard EPC C-rated property.

The catch is that electricity currently costs roughly four times more per unit than gas. On a like-for-like basis with a Part L 2021 new build, which is already fairly efficient, the bill savings are more modest. The real beneficiaries are people moving from older, less efficient homes where the gap is far larger.

For developers, the upfront cost increase needs to be considered alongside the commercial upside: homes with A-rated EPCs, lower running costs, and future-proofed technology are increasingly attractive to buyers. The market is moving in this direction. Being ahead of it is a commercial advantage, rather than just a compliance exercise.

Case Studies

Carbon3 has delivered FHS-compliant and near-compliant installations across a range of new-build residential projects. From single-phase ASHP installations on individual plots to multi-unit developments combining solar PV, and battery storage, the approach is always the same: design for compliance from day one, not retrospectively. See our case studies here.

What Should You Do Now?

Whether you are trying to future-proof your organisation’s development pipeline, or a managing compliance across a portfolio, it is the time to engage with the FHS, not in March 2027.

Here is a practical starting point:

• If you have projects in design now, check whether your SAP assessor is modelling to FHS standards, even if your planning application was submitted before the deadline. Getting your spec right now prevents expensive redesigns later.
• If you have un-commenced plots, confirm whether they rely on older transitional arrangements (2013 or 2021). Those provisions have been revoked. You may need to re-assess.
• If you are procuring heat pumps and solar, start conversations with installers early. Supply chains are tightening as the industry scales up to meet demand.
• If you are managing the cost conversation internally, the running cost story for heat pump and solar-equipped homes is genuinely compelling. The numbers are worth presenting clearly to finance and procurement colleagues.

Carbon3 works with developers from design stage to handover, handling SAP assessments, technology specification, installation, and commissioning. If you want to talk through your specific project, get in touch.

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