Five things we’ve noticed about the Future Homes Standard

April 2026

It’s been a long wait, but the Future Homes Standard (FHS) is finally here. From March 2027, homes will need to produce 75-80% less carbon emissions than those built under 2013 regulations. It will take time for everyone to get to grips with the new requirements, but here are five things we’ve noticed straight away in the newly updated, newly named Approved Document L: Energy and Greenhouse Gas Emissions:

1. Three targets, but fabric comes first

New homes must meet three performance targets: The Target Emission Rate (TER) for operational CO2, the Target Primary Energy Rate (TPER) for total energy use, and the Target Fabric Energy Efficiency rate (TFEE) for thermal performance. The TFEE can only be met by designing and building a thermal envelope that is energy efficient and airtight, with minimal thermal bridging.

While the TER and TPER are primarily met through renewables and low-carbon heating, the performance of the building fabric also influences both targets, by reducing energy demand and ensuring heat pumps run efficiently. For this reason, the building fabric should always come first.

2. Details matter more than ever…

When the fabric comes first, details are even more critical. Airtightness limits are lower under the new standard, and the requirements make it clear that thermal bridging needs to be minimised as much as possible. Details are always the riskiest area in the envelope for air leaks and thermal bridging, so the new guidance advises avoiding complex details where possible and only using details from independently verified databases. Material choice is also a factor. Loose fill or flexible insulants such as glass mineral wool can make it easier to maintain thermal continuity and achieve a tight fit around tricky details.

3. …as does real performance

The shift towards proving as-built performance was first made in the 2021 update to Part L, with the introduction of the Building Regulations England Part L (BREL) report. This report is required at the design stage and again once the building is finished, placing far greater emphasis on delivering the design intent on site.

The Home Energy Model (HEM) will eventually replace SAP 10.3 as the primary calculation methodology, enabling a more detailed and dynamic assessment of performance. Crucially, compliance must be demonstrated both before construction and at completion, with results submitted to building control at each stage.

4. Notional isn’t necessarily optimal

A feature of both the 2021 update to Part L and the new standard is the notional dwelling. This can act as a performance benchmark for design and construction of a new home, but it isn’t the only route to compliance. In practice, the notional dwelling can be restrictive and doesn’t account for additional performance factors in the fabric or interactions with other parts of the Building Regulations.

Future homes must meet the TFEE, and how you get there should be optimised for cost, buildability, embodied carbon and other performance factors. 

5. Fabric compliance doesn’t have to be complicated

The new regulations may feel like a significant step change in requirements and complexity, but the good news is that there is an optimised, standardised fabric specification that is suitable for most house types.

For example, 500mm of glass mineral wool insulation in the loft and 150mm of glass mineral wool in masonry cavity walls will meet the TFEE in most cases and comes with additional benefits. Glass mineral wool has the lowest levels of embodied carbon of any mainstream insulation material manufactured in the UK, is non-combustible and offers acoustic performance comparable with rock mineral wool.

This approach offers supply chain simplicity, on-site efficiency through a form that’s easier to build, and reduced costs per plot and per site. In short, it’s an optimised approach to future homes.