My understanding of the picture as of June 2025…

The Future Homes Standard is the next ‘uplift’ to Approved Document L (Conservation of Fuel & Power) of the UK Building Regulations.

The current standard, the 2021 Edition, was introduced in June 2022.

The Future Homes Standard is expected to be published in the Autumn of 2025 and come into effect sometime in 2026 with a transitional period of 12 months.

The ‘fabric’ standards, i.e. the u-values of floors, walls, roofs, door and windows, are expected to remain unchanged from the current (2021) standards.

There will still be a ‘Notional’ model, which dictates the target levels of efficiency and emissions. We are pretty certain that this will be based on a heat pump whereas currently it’s based on a gas boiler. It will therefore become unfeasible to specify any kind of fossil fuel boiler.

It has recently been announced that the FHS will include the requirement to provide renewable electricity generation for all dwellings, this is in the vast majority of cases will be solar (PV) panels. An array area equivalent to 40% of floor area has been mooted but yet to be confirmed.

The Home Energy Model (HEM) will become the new method of assessing compliance with Part L, replacing SAP. The FHS and HEM will be implemented at the same time.

There will be a transitional period where an updated version of the SAP methodology (SAP 10.3) can be used as an alternative to HEM. The two routes to compliance will run concurrently for a limited time before SAP is finally retired.

HEM will require a significantly greater amount of data input over SAP 10.2. The measurement of the dwelling is fundamentally different, for example the dwelling is split into two zones with elements assigned to each separately and openings are broken down to their individual components.

Additional information on ventilation will be required, including ductwork form, lengths and insulation type and thickness as well as details of air bricks and trickle vents.

More detail on space and water heating is expected to be required such as sizing and thermal mass of heat emitters, details of all hot water outlets, lengths of primary and secondary pipework.

HEM will consider the precise location, orientation and height above sea level as well as shading from neighbouring buildings.

The PCDB (product characteristics database) which holds data on heat pumps and ventilation systems etc. will need to be redeveloped for HEM.

Existing SAP assessors are likely to require additional training and certification which will be provided by existing accreditation bodies.

The introduction of the FHS and HEM is expected to be implemented alongside an updated EPC rating system and new look certificate following the government’s recent EPC reform consultation.

In conclusion, HEM, in terms of level of detail, will be along the lines of a PassivHaus assessment and therefore much more in-depth than SAP. Whereas SAP is what you could describe as a form filling exercise, I think it’s most likely that HEM will become a dynamic assessment using existing or bespoke 3D modelling software.

As with PHPP it will likely still be possible to manually take off and enter information into HEM, but for an assessor to maximise efficiency, and therefore competitive pricing, I think this option will quickly become obsolete.

…more as it happens.