This does not apply to work subject to a building notice, full plans application or initial notice submitted before that date, provided work is started on site before 15 June 2023.
Part L of the Building Regulations (England and Wales) contains requirements relating to the conservation of fuel and power. It sets the standards for the energy performance and carbon emissions of new and existing buildings.
The better insulated a window is, the lower the U-value will be
Replacements & Extensions to Existing Homes
Replacement windows and doors can't have worse performance than the elements that they replace.
New Homes
Builders may specify products with lower U-values than these, as new build thermal performance is calculated on complete building envelopes.
The limiting value is 1.6.
