Building Regulations and Window Energy Ratings
3) Are components exchangeable?
If the IG products detailed in a pre-registered WER are not on your IG supplier component list, it may be that other components on this list are exchangeable within a registered WER. The standard rule is that some components such as spacer bar and sealant can be exchanged for recognised ‘same’ or ‘better’ performing products without requiring a new simulation and subsequent WER application. Either way, don’t dismiss the prospect of using a pre-registered WER. Use product comparator tools as recommended by WER providers and liaise with your IG supplier to explore the possibilities.
The BFRC will soon launch an online tool for substitution and registering simulations.
Building Regulations and WERs Page 9