U-values explained

Windows that have an energy rating will have the u-value of the window displayed on the energy label. A u-value is a measure of how easily heat can pass through a material. Materials that let out more heat have higher u-values whereas materials that let less heat pass through them have lower u-values.

In some cases, windows with a higher energy performance rating might have a higher u-value than windows with a better energy efficiency rating. This might seem the wrong way round as lower u-values indicate better insulation levels. However, in these cases it will be that there are other aspects of the window that make them better overall such as coating used on the glass and the gap between the glass panes.

St James Traditional Joinery now includes everything you need to comply with energy ratings.

  • Automatic calculation of U-values
  • Declaration of performances
  • U-value certificates
  • Verified by bsi. UK notified body

St James u-value certificates give you the confidence that your joinery complies with legislation.