Existing Non-Dwellings

Existing Non-Dwellings (England)

Part L
Changes to the regulatory requirements for the energy efficiency of existing buildings other than dwellings are expected to have an impact upon glass and glazing products.

Published on 15th December 2021 and coming into force on 15th June 2022, the government has set out its new requirements for Part L (conservation of fuel and power) of the Building Regulations and the supporting Approved Document for existing non-dwellings in England.

The 2021 edition of Approved Document L Volume 2 has made changes to the fabric performance of replacement elements in existing buildings, including a reduction (improvement) in the window U-value.

The table below summarises the maximum U-values for new elements in extensions to existing buildings other than dwellings and new or replacement elements in existing buildings other than dwellings:
 
Element
Maximum U-value (W/m2K)
Windows in buildings similar to dwellings*
1.6 or minimum WER Band B
All other windows, roof windows and curtain walling
1.6
Rooflights
2.2
Pedestrian doors (including glazed doors)
1.6
*for example, student accommodation and care homes

WER, Window Energy Rating, is generally considered a better indicator of the energy performance of a window in an existing dwelling or similar building because it considers a range of parameters, including the useful solar heat gain.  The U-value is the total U-value of the window, taking into account both the glass and frame.

The U-value of a rooflight should be based on the outer developed surface area, which is often greater than the area of the roof opening.  Unlike for windows and roof windows, rooflights should have their U-values calculated based on a horizontal position.

No maximum U-value has been set for display windows and similar glazing for existing buildings.

Approved Document L Volume 2 also includes an alternative if windows or fully glazed external pedestrian doors cannot meet the above requirements because of the need to maintain the character of the existing building.  In such cases, they should achieve or better a centre pane U-value of 1.2 W/m2K or be upgraded to low emissivity (low-e) secondary glazing.

Pilkington manufactures a range of low emissivity glass for thermal insulation that can help windows, doors and curtain walling to achieve low U-values.

To help mitigate the risk of overheating during summer, Pilkington provides a range of solar control glass for reducing solar gains in buildings, while maintaining high levels of daylight.

The 2021 editions of Approved Document L Volumes 1 and 2 can be downloaded from here.

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

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