The Future Homes Standard is here and Airtightness Testing Is Now Non-Negotiable

The Future Homes Standard (FHS) and Future Buildings Standard (FHBS) were published on 24 March 2026, and they set out exactly what the name promises: a standard for the future of UK homes and buildings. Not just lower carbon, but higher quality, better measurement, rigorous testing and genuine compliance with airtightness testing sitting right at the centre of it.

For anyone working in energy assessment, building control, or construction, the message is simple: design intent is no longer enough. What gets built has to be proven on site.

Conversions and extensions: a gap worth closing with best practice

Here’s a nuance worth flagging, because it’s easy to miss: the Future Homes Standard is a new-build standard. As currently drafted, it doesn’t extend a mandatory airtightness testing requirement to conversions and extensions in the way it does for new dwellings, that work continues to sit under the existing Part L rules for existing buildings, where a test is only triggered in specific circumstances (such as larger glazing areas or renovations involving significant airtightness measures).

An extension or conversion still introduces new junctions, new penetrations, and new interfaces with existing fabric, exactly the places where air leakage happens. Our strong recommendation, and increasingly the mark of a professional job, is that airtightness testing should be carried out on every project, not just where it’s strictly mandated. Waiting for the regulations to catch up isn’t a reason to skip the check, it’s a reason to lead on it. Clients, developers and self-builders are increasingly asking for it anyway, because a tested building is a building nobody has to guess about.

Part F: ventilation isn’t a separate conversation anymore

Tighter airtightness and ventilation have always been linked, under the FHS, that link becomes unavoidable. The updated Approved Document F (2026) classes any FHS-compliant dwelling with a design air permeability below 5 m³/(h·m²) at 50 Pa as “highly airtight.” Cross the threshold from “reasonably sealed” to “highly airtight,” and the ventilation strategy that would have been adequate before may no longer be sufficient.

This is the practical, cross-impacting reality assessors and installers now have to work with:

• Seal it tighter, and you must ventilate it better. As uncontrolled air leakage falls, mechanical ventilation increasingly becomes the only reliable route to good indoor air quality, natural infiltration can no longer be relied on to do the job.
• Design and commissioning have to talk to each other. Part F 2026 puts far more weight on how ventilation systems are actually installed, commissioned, verified and understood by the end user, not just how they’re specified on paper. Ductwork routing, noise, and airflow verification all move from “nice to have” to expected practice.
• Performance gaps are usually installation gaps. Industry evidence consistently shows that shortfalls in real-world performance come from poor installation or lack of user understanding far more often than poor design. A perfectly designed MVHR system commissioned badly will underperform and nobody will know unless it’s tested.

In short: airtightness testing and ventilation commissioning are now two halves of the same compliance picture. Get one wrong and the other can’t compensate.

Where this leaves the skills conversation

None of this works without people who know how to test, verify and commission to these standards. The Future Homes Standard is, at its heart, a skills challenge as much as a technical one every new build project will need a qualified airtightness tester, and every assessor working across new build, retrofit, conversions or extensions needs to understand how Part L and Part F 2026 now interlock.

That’s exactly what our Next Level initiative is built for, helping members build the practical, up-to-date competence the FHS demands, from airtightness testing through to ventilation and SAP 10.3 compliance. Members currently have 20% off Next Level courses, with the offer running to the end of September 2026. A good moment to close the gap before the March 2027 deadline starts to bite.

The Bigger Picture

Strip away the acronyms and compliance dates, and the message of the Future Homes Standard and Future Buildings Standard is straightforward: this is the standard being set for the future of UK homes and buildings, and it’s built on quality, measurement, testing and verified compliance, not good intentions. Airtightness testing is one of the clearest, most measurable expressions of that shift. Getting it right, on every project, not just the ones where it’s mandatory is how the industry proves it’s ready for what comes next.