Download your free guide to Approved Document L

Approved Document L Guide for Supafil 34

Knauf Insulation's 2023 guide to Part L

We’ve developed this guide to help you navigate the latest updates to Approved Document L, or ‘Part L’, of the Building Regulations for England.

“I hope this guide will be a valuable tool, not only for achieving compliance, but in raising the bar for quality and performance across the housebuilding sector.”

Neil Hargreaves, Managing Director, Knauf Insulation Northern Europe

Neil Hargreaves

Inside, you'll find...

Approved Document L: What’s New for Housebuilders?

An overview of the key Approved Document L changes affecting Housebuilders in England. Learn about the new requirements, including carbon reduction, the Building Regulations England Part L (BREL) report, and photographic evidence. We also outline two key routes to Part L compliance.

Part L U-values

Key information on the Part L U-value requirements. We’ve included an explanation of ‘limiting Part L U-values’, along with a handy table detailing the maximum U-values for walls, roofs, floors, and party walls.

Did you know? We’ve developed a free online U-value calculator and Psi-Value calculator, to help you generate detailed, product-specific calculations for your builds.


Pitched roof U-values

Advice on typical pitched roof U-values for products such as Knauf Insulation’s Loft Roll 40, Loft Roll 44 and Rafter Roll 32 in both warm and cold roof applications. We’ve included our recommended pitched roof U-values for compliance with Approved Document L.

If you’re looking for a warm or cold roof U-value calculator, why not try our free online tool?


Masonry and timber frame wall U-values

Advice on typical U-values for walls, both masonry cavity and timber frame, using products such as Knauf Insulation’s Supafil® 34 and Supafil® Frame. We’ve included our recommended U-values for timber frame walls and cavity walls to help with Part L compliance.

Looking for a cavity wall U-value calculator? Why not try our free online tool?


Compliance recipes for Approved Document L

Inside our free guide, you’ll find a wide variety of example whole-house recipes*, designed for Part L compliance. Covering different options for 4 and 5 bed detached houses, 3 bed semi-detached houses, 2 bed bungalows, and 1 bed apartments.

Recipes feature a variety of Knauf Insulation products, including Loft Roll 44, Supafil® 34, Supafil® Party Wall, and OmniFit® Roll 34.

*Example recipes have been produced using SAP 2012 software and are intended for illustrative purposes only.

Part B: What’s new for Housebuilders?

An overview of recent key changes to the Part B Building Regulations (Fire safety) for England. Learn about some of the new requirements around combustible and non-combustible materials, affecting Housebuilders and Approved Document B compliance.


Part O: What’s new for Housebuilders?

An introduction to the new Part O Building Regulations (Overheating) for England. Learn about the two methods Housebuilders can choose between for Approved Document O compliance.

A look ahead

Key information on the Future Homes Standard and Building Safety Act. We also look at the industry’s growing focus on the issue of embodied carbon and recommendations from organisations such as RIBA and the UK Climate Change Committee. 

Download your free guide to Approved Document L

Approved Document L Guide for DriTherm Cavity Slabs
Want info on DriTherm® Cavity Slabs and Part L?