What Changes in the 2026 Building Regulations Part L Update?

What Is the 2026 Part L Update?

On 24 March 2026 the government laid the Building Regulations etc. (Amendment) (England) Regulations 2026 and published new 2026 editions of Approved Document L (Volumes 1 and 2) and Approved Document F Volume 1. Together these implement the Future Homes and Buildings Standards, the long-planned successor to the 2021 uplift. The new requirements apply in England from 24 March 2027, with transitional arrangements running to 24 March 2028.

What Changes for New Homes

• Low-carbon heating: compliance targets are calculated against a notional dwelling that uses a heat pump, and the government states that new homes will be built with low-carbon heating, high levels of energy efficiency and, in most cases, solar panels.
• Solar PV (new requirement L3): when a building which is or contains a dwelling is erected, a system for on-site renewable electricity generation must be installed on the building or within its curtilage. The guidance benchmark is a photovoltaic array with installed peak power equivalent to panels of 0.22 kWp per m² covering at least 40% of the ground floor area, oriented between south-east and south-west at a 45 degree pitch and not overshaded. Exceptions apply where the design or surroundings prevent a reasonable output.
• Heat pump installation (new Section 8): heat pump installation work must either be self-certified by a registered competent person or certified by a building control body, with inspection and testing against the standards in the approved document.
• New calculation method: the Home Energy Model (HEM) is approved for demonstrating compliance alongside the Standard Assessment Procedure (SAP 10.3).
• Home User Guide: owners of new dwellings must be given a non-technical guide covering how to operate and maintain the home and its heating systems.

The limiting (backstop) U-values for new dwellings are unchanged from the current edition: walls 0.26 W/m²K, roofs 0.16, floors 0.18, windows and doors 1.6. In practice new homes are specified well past these backstops, because compliance is driven by the notional dwelling rather than the limiting table.

Key Dates

What It Means for Extensions and Renovations

Very little changes on site for work to existing homes. The limiting U-values for new fabric in existing dwellings carry over unchanged, renumbered from Table 4.2 to Table 3.2: walls 0.18 W/m²K, floors 0.18, roofs 0.15, and windows 1.4 or Window Energy Rating Band B minimum. The renovation standards for existing thermal elements (now Table 3.3) also keep the same threshold and improved values, for example a roof being renovated or retained should be brought to 0.16 W/m²K where feasible.

Replacement boilers in existing homes remain permitted: the 2026 edition keeps minimum efficiency tables for gas-fired and oil-fired heating systems in existing dwellings. Dwellings created by converting another building (a material change of use) keep the current limiting standards for now; the government has said it plans a further consultation on those.

Check a proposed wall, floor or roof build-up with our U-Value Calculator, size the insulation with the Insulation Thickness Calculator, and see how the targets have moved over time in our Part L target U-values history reference.

Where It Applies

This update applies in England only. Wales and Scotland set their own building energy standards separately. The details above are drawn from the 2026 edition of Approved Document L Volume 1, Building Circular 01/2026 and the government response to the Future Homes and Buildings Standards consultation, all published on gov.uk on 24 March 2026. This page is a plain-English summary, not the regulations themselves: confirm the details for a specific project with your building control body.