Understanding the changes to Approved Document L

Approved Document L is a building regulation in England setting standards for the energy performance of new and existing buildings. The updated standards came into effect on 15th June 2022. The grace period for any notices or plans that had been submitted before this date ending on 15th June 2023. 

These changes are a transitional step in the work towards the Future Homes Standard and Future Buildings Standard which are due to be implemented in 2025. The aim is to future proof buildings as part of the government’s goal of achieving net zero greenhouse gas emissions by 2050. 


What are the changes to Approved Document L? 

The changes to Approved Document L state that buildings must be built to a minimum standard of total energy performance. The metric used to determine this is ‘Target Primary Energy Rates’ (TPER), which is the maximum primary energy use for the building per year, measured in kWhPE/m2. This metric incorporates the energy required to provide heating and hot water to a newly built building. It also includes lighting, ventilation, cooling systems and showers. 

Architects need to utilise a ‘fabric first’ approach to designing buildings in order to achieve the airtightness and thermal performance required to meet the TPER. 


What is a fabric first approach? 

A fabric first approach considers the building envelope, the materials used and the maximisation of their performance. It’s key that the materials to be used in the construction are fully considered at the design stage as this affects planning applications. 

The updates now require all dwellings to be air tested and to provide onsite evidence including photographs of the installation. It’s key that the fabric is first considered at the very early stages of a project and that everyone from architects to installers understands the changes to the regulations in order to ensure that buildings are compliant. 


What does this mean in practice? 

For a new build, Approved Document L states that “to ensure continuity of the air barrier, window and door units should connect to the primary air barrier and window and door frames should be taped to surrounding structural openings, using air sealing tape. Compressible seals or gun sealant may be used to supplement taping.’’ 

It’s important to balance sufficient air and water tightness with good vapour control. Helping to minimise the risk of moisture build up, which could result in problems with damp and mould. 


At PAL, we supply a range of suitable products by illbruck! 

The innovative BBA certified i3 system is a three-level approach for the perimeter sealing of windows. This helps you to seal out the weather whilst sealing in energy savings and comes with a 10-year warranty. 


ME508 is an airtight non-woven fleece membrane for internal applications. It is self-adhesive for optimum adhesion and vapour control, with options for installing to the window frame edge or face. Part of the intelligent membrane range, ME508 Duo Membrane EW/F [Product page] [TDS] also benefits from humidity variable vapour permeability. 


FM330 Pro Foam Air Seal [Product page] [TDS] can be used around the window for tight gap filling, with a movement accommodation factor of 50% that ensures the integrity of the seal is maintained. This product provides improved thermal performance, as well as having good elasticity, air tightness and acoustic properties. 


For external application, TP600 impregnated foam tape [Product page] [TDS] provides a weather tight seal against the most severe combinations of wind and rain whilst also providing thermal and acoustic insulation. 


Illbruck’s solutions also include fire classified products, providing you with a fabric first, future proof solution. 


Get in touch with Tom today to discuss how PAL can support you with your needs. 

T. +44 7789 516858