New Dwellings in Wales

New Dwellings in Wales

Part L Wales

On 24th May 2022, the Welsh government issued new and updated Approved Documents in support of the Building Regulations for residential buildings in Wales. These changes are expected to have a significant impact on glass and glazing products in new and existing dwellings.

Taking effect on 23rd November 2022, the new Approved Document L Volume 1 Dwellings (conservation of fuel and power) includes provisions to reduce the carbon emissions and improve the energy performance of new dwellings in Wales.

The changes to the worst acceptable fabric performance values – sometimes referred to as 'backstop' values - include reducing (improving) the window U value from 1.6 to 1.4 W/m2K.  For windows, doors and rooflights in new dwellings, the new 'backstop' values are given in Table 1.

Table 1 - Worst acceptable fabric performance values in new dwellings

Element Maximum U value (W/m2K)
Windows or roof windows 1.4
Rooflight (horizontal position) 2.2
Doors 1.4

The expectation is that the U values will have to be lower than those given in Table 1 to enable new dwellings to achieve the whole building minimum energy performance target. This is highlighted in the elemental specification for the notional dwelling summarised in Table 2.

Table 2 - Elemental specification for the notional dwelling

Maximum U value (W/m2K)
Windows, roof windows and glazed doors 1.3
Rooflights (horizontal position) 1.6
Opaque and semi-glazed doors

To satisfy the above requirements, Pilkington provides a range of low-e glass that can provide thermal insulation.

To access the new Approved Documents on the Welsh government's website, please click here.

If you have any questions on Part L 2021 in Wales and what the implications might be for glass, please fill in our contact form, selecting 'Architect' or 'Trade' as the Nature of Enquiry and 'Part L' as the Enquiry Type.

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