August 2026 update.The Approved Documents are published and the dates are fixed – FHS comes into force 24 March 2027, with SAP 10.3 confirmed as the bridge tool. Here’s what’s actually changing, and by when.
For several years, the Future Homes Standard existed mostly as a set of consultation proposals – Option 1 versus Option 2, draft fabric specifications, an “expected” date that kept moving. That’s no longer the case. The government published the final Approved Documents L and F, alongside Building Circular 01/2026, on 24 March 2026, and the regulations come into force exactly twelve months later, on 24 March 2027. For housebuilders still working from the 2024 consultation documents, or assuming HEM will simply replace SAP overnight, the gap between what’s confirmed and what’s still assumed is now a genuine commercial risk.
In this blog you’ll learn:
- The confirmed key dates for the Future Homes Standards (FHS) coming into force, including the transitional arrangements for live developments
- What the Approved Documents actually require on solar PV, heating, ventilation, lighting and fabric standards
- Whether – and when – FHS catches retrofit and renovation work, not just new-build
- Why SAP 10.3 and the Home Energy Model sit on a separate timeline from the FHS in-force date, and what that means for your compliance route
What is the Future Homes Standard?
The Future Homes Standard (FHS) is the next uplift to Part L (energy) and Part F (ventilation) of the Building Regulations, aimed at cutting carbon emissions from new homes by 75-80% compared with the 2013 baseline. It follows the interim 2021 Part L uplift and replaces the consultation-stage “Option 1 / Option 2” framework with a single, confirmed notional specification.
Compliance itself is still demonstrated through SAP – specifically SAP 10.3, the current version confirmed on the government’s official SAP guidance. SAP has been the UK’s standard dwelling energy assessment methodology since 1993, updated periodically ever since (most recently in 2022 and 2026), and its two jobs haven’t changed under FHS: demonstrating Part L compliance, and generating EPCs. What has changed is the specification SAP 10.3 is now checking homes against.
Confirmed Key Dates
- 24 March 2026 – Final Approved Documents L and F 2026 editions published, alongside Building Circular 01/2026 and the government’s consultation response
- 24 March 2027 – The Future Homes Standard comes into force for standard new-build work
- 24 September 2027 – The Standard comes into force for higher-risk building work
- 24 March 2028 – The transitional period ends
The transitional arrangements matter more than they might look at first glance. Protection is granted plot by plot, not site-wide: a building notice, initial notice, or full plans application must be submitted before 24 March 2027, and physical work must then commence on that specific plot – defined as work starting on the ground-floor structure – within twelve months, by 24 March 2028. Registering an entire site in one go doesn’t protect future phases that haven’t actually started; each plot has to commence individually to keep building to current Part L 2021 standards.
What the Standard Actually Requires
Low-carbon heating
The Approved Documents don’t contain an explicit ban on gas boilers, but they cut the allowable Dwelling Emission Rate so sharply that a traditional gas system can’t realistically pass. Air source and ground source heat pumps become the default heating technology in practice, even without a literal prohibition in the regulation text. Direct electric heating (paired with high-performance fabric) and 4th-generation heat networks remain viable alternatives for specific site constraints or apartment blocks.
Solar PV
Rooftop solar PV is required under Requirement L3 wherever a plot has feasible roof space, calculated against a baseline provision equivalent to around 40% of the plot’s ground-floor area. That baseline assumes an ideal south-facing roof; off that orientation, the physical panel area needed to hit the same annual output target scales up accordingly, so orientation is no longer a cost-neutral design decision. Blanket exemptions apply for buildings over 18 metres, Higher-Risk Buildings, and heavily shaded sites achieving under 720 kWh a year. Where a plot genuinely lacks the roof area to hit the target regardless, developers can submit maximum-fit design schematics to Building Control under Section 5.7 of Approved Document L, provided the core building targets are still met.
Fabric standards
Minimum and notional fabric specifications broadly hold at 2021 levels as a legal backstop, but the notional reference targets used to demonstrate actual compliance have tightened – many window and door configurations will need triple glazing to comfortably clear the notional 1.2 W/m²K U-value target, because the assessment now uses each window’s actual size and frame layout rather than a standardised reference size.
Ventilation and lighting
Decentralised mechanical extract ventilation (dMEV) becomes the default notional ventilation strategy, with a maximum permitted Specific Fan Power of 0.3 W/(l/s) – tight enough to rule out cheaper, less efficient fan units. Lighting specification also tightens, with a notional high-efficacy threshold of 105 lm/W meaning off-the-shelf LED fittings can no longer be assumed to pass without checking manufacturer data.
Overheating (Part O)
Part O isn’t new, but FHS raises the stakes on it: tighter airtightness and larger mandatory solar arrays both increase summer overheating risk if not actively managed. Most house types can still use the simplified method (limiting glazing area, providing cross-ventilation openings), but complex or heavily-glazed layouts need full CIBSE TM59 dynamic thermal modelling to prove compliance – and there’s a genuine design tension here, since the south-facing glazing that helps solar PV yield is the same glazing that drives overheating risk.
Non-domestic buildings.
For non-domestic new-builds, the equivalent notional specification requires on-site solar PV coverage equivalent to 40% of the building’s footprint for side-lit spaces, rising to 75% for top-lit spaces.
Does FHS Apply to Retrofit and Renovation Work, Not Just New Build?
Because FHS updates Part F and Part L directly, it isn’t confined to new-build sites – it catches deep retrofit and renovation projects too, and the trigger for compliance is easy to miss.
Work officially falls under the regulations if it significantly alters a building’s fabric, energy efficiency, or ventilation. In practice, that includes a 50% threshold: any completely new element must comply with current standards, as must any existing thermal element where more than 50% of its surface area is being renovated. But plenty of everyday work triggers compliance too – replacing windows and doors, installing a new heating system, or modifying ventilation all activate Part L and Part F obligations, and it’s the developer’s responsibility to submit the necessary building notice or full plans, not Building Control’s. Sign-off from Building Control doesn’t remove liability either: the developer, builder or architect remains legally responsible for inadequate ventilation or compliance failures regardless of whether Building Control’s own checks caught the issue.
A Note for Cross-Border Developers: Wales Sets Its Own Timeline
Building regulations are devolved, so the 24 March 2027 date above applies to England only. The Welsh Government intends to introduce FHS-equivalent targets on its own separate timeline, and – based on the precedent set by the 2022 Welsh Part L uplift, which already went further than England’s – developers should expect stricter fabric standards, mandatory heat pumps and PV, and an eventual move to HEM in Wales as well. Anyone building across the border needs to plan for two regimes, two specifications and two transition windows; an England-compliant design shouldn’t be assumed to pass in Wales.
SAP 10.3, HEM and Why They’re Not on the Same Clock as FHS
This is the point that trips up most housebuilders, so it’s worth being precise about it: when HEM becomes available has nothing to do with when FHS comes into force. They’re two separate timelines that happen to overlap.
At launch on 24 March 2027, SAP 10.3 – updated with the FHS notional specifications and revised carbon factors – is the sole approved compliance methodology. HEM is not required, and isn’t yet available, on that date.
HEM’s own rollout runs on a different clock, tied to the March 2026 Approved Documents rather than the March 2027 in-force date:
- HEM was expected to become available no earlier than three months after the 24 March 2026 publication – a window that opened in June 2026
- The government delayed HEM’s launch on 8 June 2026 for final internal assurance; per its own SAP guidance page, HEM is now expected “in the coming months,” with no confirmed date
- Once HEM is approved, a minimum 24-month dual-running period begins, during which both SAP 10.3 and HEM are valid for FHS compliance
- After that window closes, SAP 10.3 will be withdrawn and HEM becomes the sole methodology – the government has committed to giving six months’ notice before that withdrawal date is set
In practical terms: you’ll be using SAP 10.3 to demonstrate FHS compliance both before and for some time after the 24 March 2027 in-force date. HEM doesn’t arrive at the same moment the regulations do.
For the full detail on HEM’s own rollout, data requirements and current status – this is the natural next read once you’re past the “how does this affect FHS” question above:
Our Expert Insight: our technical team’s view is that the real risk here isn’t the eventual switch to HEM – it’s treating “FHS in force” and “HEM available” as the same event. Housebuilders who assume HEM will simply be ready and waiting on 24 March 2027 risk being caught out if it slips further, exactly as it already has once.
What’s Next?
The Future Homes Standard is no longer a moving target – the dates are confirmed, the Approved Documents are published, and the only genuinely open question is when HEM itself becomes available. For housebuilders, that means the practical work now is modelling standard house types against SAP 10.3 well ahead of March 2027, rather than waiting to see what HEM brings.
If you’d like your standard house types stress-tested against the confirmed FHS targets before March 2027, our team can talk you through what that looks like for your portfolio.
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