Part L changes 2022 – what you need to know

In December 2021, the changes to UK Building regulations were published and outlined the Part L changes 2022. These come into force on 15th June 2022, focusing on lower U-Values and better Energy Ratings for doors and windows in new build, existing dwellings and commercial buildings. These Part L changes 2022 focus on cutting emissions from a property and especially new homes now and in the future.

This is general advice as we understand it and in all cases, please consult the relevant building professional.

Part L changes 2022 – the changes

From June 15th 2022, the changes you need to be aware of regarding doors and windows are as follows:

For new build properties, a lower U-value of 1.6 W/m2k for windows and doors.

For door and window replacements in existing dwellings, The U-value will be 1.4 W/m2k maximum for windows and 1.4 W/m2k maximum for doors, where doors have for than 60% of internal face glazed. It’ll be 1.4 Wm2k for all other doors.

For commercial buildings that are similar to dwellings, the new Part L changes 2022 are 1.6 W/m2k for windows in buildings. Curtain walling and any public/pedestrian doors also need to meet 1.6 W/m2k.

These Part L changes 2022 are part of the Approved Documents, specifically for glazing, Part L (‘Conservation of Fuel and Power’).

This means U-value energy ratings will be upgraded on ALL windows & doors for new and existing buildings, to make them more thermally efficient.

Part L changes 2022 vs 2021

The key differences between the June 2022 and previous requirements under Approved Document L, improve (lower) the U-Values for both new and replacement windows and doors in property.

We understand new build projects will fall under SAP 10 (Standard Assessment Procedure) method. As a result, the U-Values mentioned above must now be met.

How Part L changes 2022 affect you and your projects

As we understand the changes, for existing dwellings, you can continue to use the same high specification glass with a low U-Value. With our Cortizo system folding sliding doors going into many new build projects,

For new dwellings and a lower U-Value, you’ll need glass with a Ug-value of 1.0 to comply with the requirements of Part L changes 2022.

As our customers and we use different glass suppliers, the product descriptions of suitable glass may vary, so please consult with your glass provider. Generally speaking, your glass needs to be a Ug-value of 1.0 if you want to comply with both new build and existing dwellings requirements comfortably.

How do our products meet the new Part L changes 2022?

The Cortizo bifolding door has been reduced in profile sizes from 120mm to 100mm. This means less aluminium and more glass. The greater use of glass, therefore, improves the previous figure of the doors, which we are advised by Cortizo Systems, gives a suitable C rating, depending on which calculation method is used.

The benefit of this, aside from meeting the new Part L 2022 requirements, is an even slimmer bifold for your property projects, thinner than most of the leading bifold door systems.

As our Cortizo single and French doors also use the same profiles and glass combination, these should also comply.


Here’s a summary of the U-Values and Energy Ratings you need to know.

For replacements and extensions to existing dwellings:

Windows, U-Value of 1.4Wm2K or B WER.
Doors with more than 60% internal face glazed, 1.4Wm2K or C DER.
Doors, 1.4Wm2K or B DER.
External Fire Doors, 1.8Wm2K, no DER.

Replacement windows and doors must not have a worst performance than the outgoing windows.

New Homes

Windows, U-Value of 1.2Wm2K.
Doors with more than 60% internal face glazed, 1.2Wm2K.
Doors less than 30% glass, 1.0Wm2K.
Doors with 30-60% glass area, 1.0Wm2K.

With many new build homes calculated as complete buildings, it’s possible to provide windows with better U-Values, but the limit we understand to be no worse than 1.6Wm2K.

You can view the official documentation for Part L.

Cortizo bifolds already comply with the new Building Regulations

Our BF73 system for bifolding doors is DER rated C for existing properties & meets the new build requirement of 1.6 W/(m2k), using centre pane values of 1.1 glass.