New and replacement external doors, windows and screens are manufactured, glazed and certificated to meet the conservation of fuel and power Building Regulation though the CERTASS Ltd scheme. This Building Regulation specifies that replacement windows for existing dwellings must achieve a minimum windows energy rating (WER) of band C for a whole window U value of 1.6 W/m²K is required.

To facilitate this, glazing is carried out with the use of 24mm double glazed units comprising of two layers of 4mm glass and a 16mm argon filled cavity. Incorporating warm edge bars and high performance low "E" glass coating to the inner pane. This gives a typical system U value of 1.2 W/m²K

Top Notch Joinery is able to supply window products and doors with U values lower than 1.6 W/m²K. We are also able to provide calculations of U-values on request.