Assessing Rooflight Thermal Performance
Rooflights have historically had their U-value assessed in the vertical plane (as for a window). This has now changed in the revised Approved Document L and rooflights should now be assessed in the horizontal plane – which will influence the U-value. If the only U-value available is that assessed vertically there is a conversion table available in BRE document BR443 which is available on this page.
Rooflights For Dwellings
The rooflight limiting U-value is 2.2 W/m2K when assessed in the horizontal plane (previously assessed in the vertical plane), this is for both new and existing dwellings.
The SAP notional building uses an improved rooflight
U-value of 1.7 W/m2K (assessed horizontally).
Rooflights For Buildings Other Than Dwellings
The limiting rooflight U-value is 2.2 W/m2K when assessed in the horizontal plane (previously assessed in the vertical plane), this is for both new and existing buildings.
The SBEM notional building uses an improved rooflight U-value of 2.1 W/m2K (assessed horizontally).
Our 4Edge Pro, Skyline Box, Skyline & Rafterline patent glazing systems all meet with Building Regulations Part L compliance.
