Because 25% of the energy in a house is lost through the windows, insulation of the windows is particularly important.
The transfer of energy through the windows consists not only of heat-loss but also, due to the transparency of glass, of energy gain. With suitable planning the window areas can be so arranged (large areas facing south) that they influence the energy balance of the building and heating costs are reduced.
The heat insulation of windows depends upon frame materials, insulated glass and the efficiency of the window seal.
The U-value is the standard measure for the insulation properties of the window. The lower the numerical value, the better the insulation. It is possible to improve the U-value by the addition of roller-blinds or shutters. Further information about the insulation values of our window systems can be found under [windows] and also under tips - [saving energy]