Improving your window's energy rating can help cut your bills

Why are energy ratings important?

All windows should have an energy rating to enable you to compare their performance, in the same way as for white goods. The scale goes from A+, for the best performance, to G - but a rating of C or above is required to comply with building regulations. 

All Anglian windows are independently assessed by the British Fenestration Rating Council (BFRC) and meet this standard. In fact, most exceed it, offering ratings of B, A and A+.

Windows are rated according to three key factors:

  • Draught prevention: The L-value shows how airtight the window is by measuring air leakage – look for a zero.
  • Ability to harvest heat from the sun: A window's solar factor (G-value) shows how much heat is gained from sunlight passing through the glass. It's expressed as a number between 0 and 1, the nearer 1 the better
  • Efficiency at retaining warmth: Look at the thermal transmittance (U-value) to see how well a window stops heat escaping from inside – the lower the figure the more efficient it is.

The combination of all three numbers gives you the Energy Index and the overall energy rating.

Thermal transmittance Solar factor and air leakage illustrations