The Window Energy Rating (WER) tells you 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. The scheme is similar to those seen on household appliances, white goods and light bulbs.
up to 25% of the heat within most homes escapes through the windows
Considering the fact that up to 25% of the heat within most homes escapes through the windows, it’s worth considering installing new energy-efficient windows in order to save energy and hence money off your energy bills. More and more people are opting for A or A+ rated windows as an energy saving measure.
A window’s rating is determined by a formula which takes into account the total solar heat transmittance, the amount of the sun’s heat which can pass through the glass (usually referred to as g-value); the U-value of the whole window (frame and glass combined), how well the window keeps the heat in your home; and the air infiltration through the window seals. To make the Rating standard across all products, a standard window size and configuration is used. The resulting value is then placed into a band on the scale G-A, with A-rated windows being the most energy-efficient. This makes the system of rating windows consistent with other products which have energy performance labels such as those that will be familiar on washing machines, light bulbs and refrigerators.