circle arrow
building testing window & door testing Product Certification about contact
U-value & energy ratings
ukas testing
bfrc logo

U-value calculations

U-value calculations (sometimes referred to as heat transfer coefficients or thermal transmittances) are used to measure how effective the components of a building’s fabric are as insulators i.e. preventing heat from transmitting between the inside and the outside of a building.

As energy prices continue to soar and the awareness of sustainable buildings continues to grow, performance measures such as u-values are becoming increasingly important. Compliance with building regulations requires lower than ever u-value performance, which means changes in the design of buildings, both in the use of materials (e.g. insulation), the make up of the building elements (e.g. cavity walls and double glazing) and the overall make up of a building's fabric (e.g. reducing the proportion of glazing).

Build Check is accredited by UKAS to undertake u-value calculations for windows and doors to meet the requirements of the building regulations, Part L. Our engineering team can also help to design a cost-effective research and development programme to help you maximise the performance of your windows and door products to your specific requirements.

If you want to calculate your own u-values to demonstrate Part L compliance, Build Check’s Oracle u-value calculator is available to members on a subscription service.

Window Energy Ratings

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.