Document L Legislation for Energy Performance of Windows
Document L has been put in place in order to bring the UK in line with the EU’s Energy Performance of Buildings Directive and addresses. In this instance, the domestic conservation of fuel and power.
As of 2010, approved document L legislation now applies to both new builds and replacement windows and aims to reduce fuel consumption. The quantity of heat which escapes through a closed window is measured in U-Values; the lower the U-Value the less heat lost.
It is the home owner’s responsibility to ensure that any work they have carried out on their property is compliant with UK Regulations and Standards. In respect to double glazing, the easiest way to do this is to use a reputable supplier and installer registered with a self-certifying body such as FENSA or CERTASS. They will ensure that Building Regulations are adhered to and arrange for the necessary certification once the work is complete.
The current technical guidance provided to installers in document L sets the overall U-value average for windows at 2.0. Note that there are instances concerning listed buildings or properties within conversation areas where this legislation does not apply.