Window Energy Ratings LF Windows Blog Vince Aug 04 2020 Window Energy Ratings (WER) is a scheme first launched by the BFRC (British Fenestration Ratings Council) and Certass launching similar schemes soon after. A WER provides independent verification of how energy-efficient your windows are. The rating system is based on a scale of G to A+, with A+ windows being the most energy-efficient. Build Check is an approved Independent Agency (IA) for the BFRC (British Fenestration Ratings Council) and as such, we employ a number of BFRC accredited simulators who are qualified to calculate the energy performance of windows. We can offer simulation based WER calculations as an alternative to physical testing (e.g. hotbox testing) which gives window manufacturers the advantage of being able to alter product designs to achieve the desired performance criteria in a simple and cost-effective way. On completion of the simulation, you can use the results as part of the certification process to gain an energy rating for your products.