From 2027 new homes will no longer use fossil fuel heating, with the aim being that they will not need major energy upgrades to align with the national net zero strategy. For clients, this marks a clear shift in how projects will need to be planned, costed and delivered.

What is changing?

Part L 2026 moves beyond simply reducing energy use and instead focuses on cutting greenhouse gas emissions. Heating and hot water will now need to be powered by electricity, meaning low carbon systems such as heat pumps or communal and district heat networks and PV panels must be integrated from the very start of design. This early shift in thinking will influence land use, servicing strategies and cost planning.

What stays the same?

Although earlier consultation suggested much stricter fabric standards, the Government has confirmed that the minimum fabric requirements will remain broadly aligned with Part L 2021. Compliance will depend on good insulation, airtight construction and thoughtful detailing to minimise heat loss at junctions. Fabric is still important, but low carbon heating and renewable energy will carry more weight in meeting the new carbon targets.

What becomes standard practice?

Gas boilers will no longer be permitted in new homes. All developments will need to plan for air source heat pumps or low carbon heat networks. This affects plant space, electrical capacity, acoustics, and supply chain engagement, all of which will need to be considered earlier in the development process.

A key change is the much larger requirement for solar PV. Most new homes will now need panels sized to around 40% of the ground floor area. In practice, this makes PV a core design driver. Roofs will need to maximise usable area and avoid shading.

How compliance will be shown?

Design teams can demonstrate compliance using SAP 10.3 or the new Home Energy Model (HEM). HEM is more detailed and requires more information, which means earlier decisions and closer coordination between disciplines but this is intended to give more accurate predictions of real world energy performance.

When it applies?

The new rules take effect from 2027, with transitional periods in place for projects already in progress. From 24 March 2027 the rules apply to new non-high risk buildings, and from 24 September 2027 they apply to high risk buildings. Typical housing schemes will benefit from a one year lead in and one year transition period. In reality, any scheme now entering early design is likely to be built under the new standard.

What it means for your projects?

Developers for new housing should now consider:

• heat pumps or heat networks on every new scheme
• solar PV on most roofs
• earlier design coordination to meet HEM requirements
• reviews of site layouts, plant space and electrical capacity

In simple terms, Part L 2026 means cleaner heating, more solar and homes that are more future proof and cheaper to run. The direction of travel is clear and gives greater certainty for long term planning.

Further information

Contact Taby Halliwell or Mat Naccarato

Part L 2026 Future Homes and Building Standards Guidance Note