Window Energy Rating – the facts

What is the WER?

WER stands for Window Energy Rating. The Window Energy Rating system was launched in March 2004. It was set up by the British Fenestration Rating Council (BFRC) – an independent government-supported body which was formed to develop and administer a window energy rating system in the UK. The WER tells you how efficient your windows are at preventing heat from escaping your home.

How is WER calculated?

The WER rating system is based on a scale of G to A+, with A+ windows being the most energy-efficient, and G the least. A window’s rating is calculated using the following three values:

  • Heat loss, or the U value: how much heat a window transfers
  • Solar gain, or the G value: how much solar heat can pass through the glass
  • Air leakage, or the L factor: how penetrable windows are to the air

To ensure that the WER is equal across all windows on the market, a standard window size and configuration is used when calculating the energy efficiency. This is because larger windows will be less energy efficient than small ones simply due to their increased surface area.

The Window Energy Rating and label apply to the whole window – the frame and the glass. The rating does not apply to the individual parts as they are rated once together to form a whole structure.

The WER uses a similar rainbow label to the ones you might see on white goods, which makes it easy to understand at a glance how energy efficient your windows are.


Does the Window Energy Rating really make any difference?

When you consider that up to 25% of the heat from most homes escapes through windows, and that a single pane of glass can lose almost ten times as much heat as the same area of insulated wall, it’s safe to say that each window’s energy efficiency can make a big difference to your home – and your heating bills. It’s worth looking at the current WER rating of your windows. If they’re a low WER rating, that might just explain why your home is so hard to heat in winter.


What should I be looking for when choosing windows?

The standardisation of window efficiency calculations means that you instantly know how energy efficient any windows are before you buy them. You are free to make a fully informed choice thanks to an independent third party assessment.

A+ rated WER windows are the most energy efficient windows available on the market. Choosing A+ rated windows will ensure that your house heats up more efficiently in winter, and retains its warmth for longer than lower rated windows. This will save on energy bills as well as cutting your carbon emissions.

All iGlaze windows are A+ rated as standard. We also offer triple glazed units, which are even more thermally efficient than double glazing, and also help to reduce the level of noise from outside. Call us on 01767 765 440 to get a quote for your windows today