Buildings other than dwellings

Buildings other than dwellings

Part L Vol 2

On 26th September 2022, the Welsh government issued new and updated Approved Documents in support of the Building Regulations for non-residential buildings in Wales. These changes are expected to have a significant impact on glass and glazing products in new and existing buildings.

Taking effect on 29th March 2023, the new Approved Document L Volume 2 buildings other than dwellings (conservation of fuel and power) includes provisions to reduce the carbon emissions and improve the energy performance of new non-residential buildings in Wales.

Although new buildings are required to achieve a Target Primary Energy Rate and Target Emission Rate, limiting U values – sometimes referred to as 'back stop' U values – are set for some building elements to prevent poor fabric design.  The following limiting U values for fenestration elements have been set for new non-domestic buildings:

Element Maximum U value (W/m2K)
Windows 1.6
Roof windows, curtain walling
Rooflights 2.2
Pedestrian doors (including glazed doors)

Dependent upon the project design, the U values may have to be lower than the above values to enable new buildings to achieve the target rates for the building.

Limiting U values for new and replacement fenestration elements in existing non-domestic buildings are provided in the table below:

Maximum U value (W/m2K)
Buildings essentially domestic in character
All other buildings
Windows 1.4 or Window Energy Rating band B
Roof windows, curtain walling
1.8 1.8
Rooflights 2.2 2.2
Pedestrian doors (including glazed doors)
1.8 1.8

If windows or fully glazed pedestrian doors are unable to meet the above requirements in an existing building, in order to maintain the character of the building, either of the following should apply:

  • the maximum centre pane U value should be 1.2 W/m2K, or
  • single glazing should be supplemented with low emissivity secondary glazing
Provisions also need to be made to limit heat gains in the summer. For each space in the building that is occupied or mechanically cooled, solar gains through the glazing – aggregated from April to September inclusive - should be no greater than would occur through the relevant reference glazing systems.

For transitional arrangements, the new requirements do not apply to work on a particular building where a building notice, full plans application or initial notice have been submitted before that date, provided the work for each building is started before 29th March 2024.

The new Approved Document L Volume 2 for buildings in Wales other than dwellings can be found here.

If you have any questions on Part L 2022 in Wales and what the implications might be for glass, please complete our online contact form, selecting 'Architect' or 'Trade' as the Nature of Enquiry and 'Part L' as the Enquiry Type.

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