Window Energy Ratings are not a requirement of any standard, they are an aid to sales and marketing. They are helpful in ensuring customers understand the thermal performance of the window they are purchasing and can be used to prove the rating standard required by Building Regulations.
You DO need to have a thermal performance for your units or windows and this can be shown by an official WER, but there are a number of other ways to "prove" this.
Building Regulations
A change in Building Regulations (Document L1B) in October 2010 required all window installations from that date to have a thermal performance of 1.6 which is equivalent to a window energy rating of "C".
A) Spacer Bar Thermal Values
Although a small contributor to a WER, over the past few years suppliers of spacer bars have been claiming certain values. Many of these values have been disputed and to resolve the problems an agreement was reached by the Glass & Glazing Federation (GGF) and the British Fenestration Rating Council (BFRC) whereby testing must be undertaken to ensure that thermal values are comparable.
A spacer bar manufacturer now has to submit data in the form of a Bundesverband Flachglas (BF) data sheet. This now means that all values are comparable and have been subjected to exactly the same tests.
B) Sealant depth.
Sealant depth is critical to the performance of a double glazed unit. The manufacturers guidelines should be followed and the units produced should be representative of the System Description used for the Part 2 and 3 testing.
