Part L 2026 explained: the Future Homes and Buildings Standards

What was published, and when

The Building Regulations etc. (Amendment) (England) Regulations 2026 (SI 2026/335) were made on 23 March 2026 and laid before Parliament on 24 March 2026. Alongside them, the Government published the 2026 editions of Approved Document L (Energy and greenhouse gas emissions) Volumes 1 and 2, Approved Document F (Ventilation) Volume 1, and Building Circular 01/2026, which explains how the changes and the transitional arrangements are intended to work. The Approved Documents were revised on 8 September 2026 to correct minor errors, notified by Circular 04/2026, so it is worth checking you are working from the current GOV.UK versions rather than a copy downloaded in the spring.

The dates that matter

There are three dates to hold in your head: publication, commencement for ordinary work, and commencement for higher-risk building work. Publication does not change what building control will assess — it starts the clock and tells the industry what is coming. Commencement is when the new standard applies to work notified from that point onwards.

The new functional requirement: L3

The headline addition is a new functional requirement, L3, covering on-site renewable electricity generation for new dwellings and buildings containing dwellings. In practice this means solar PV becomes an expected part of a new housing scheme rather than an optional way of closing a shortfall in the calculation. The requirement itself is confirmed in the Regulations and Circular 01/2026. Specific sizing rules are set out in Approved Document L Volume 1, and we deliberately do not quote a percentage figure here until we can point you at the exact clause in the current version of the document — several figures circulating in the industry come from the consultation rather than the published guidance.

The other changes worth knowing about

Beyond L3, the Regulations make a set of changes that quietly affect how schemes are designed and evidenced. Part L is reframed around reducing greenhouse gas emissions as well as conserving fuel and power. Lifts, escalators and moving footways in new buildings are brought into the definition of fixed building services, which means their efficiency and commissioning fall within scope. And a new regulation 40C requires information to be provided to the owner of a new home.

• Part L reframed around greenhouse gas emissions as well as energy conservation
• Lifts, escalators and moving footways in new buildings treated as fixed building services
• New regulation 40C — information for new-home owners
• Guidance added on heat network compliance routes
• Guidance on limiting heat loss from low-carbon heating systems
• Minimum services efficiencies and heat pump controls
• Commissioning and certification of fixed building services
• The Home User Guide

What it means for a scheme you are designing now

If your building notice, initial notice or full plans application goes in before 24 March 2027 and work on that building starts before 24 March 2028, Part L 2021 can still be used for that building. That is genuinely useful, but it is a building-by-building test rather than a scheme-wide one, so a large phased site can straddle both standards. The practical answer is to model early: run a design-stage calculation against 2021 and sense-check the fabric and heating strategy against the direction of the 2026 standard, so that any plots that fall the wrong side of the date do not need redesigning late.

What we are not telling you yet

There is a lot of confident commentary about Part L 2026 that traces back to the consultation rather than the published documents. The carbon saving often quoted for new homes, the exact solar PV sizing rule, and the timetable for the Home Energy Model replacing SAP are all things we hold in our facts register as unverified until a primary source confirms them. We would rather give you a shorter answer that holds up in front of a building control body than a longer one you have to walk back.