Energy performance of glazings and windows

Abstract

The purpose of the work is to make it possible to compare the energy performance of different glazings or windows in an easy way. The energy performance is expressed by the net energy gain, which is given as the solar gain minus the heat loss. The net energy gain from glazings and windows both depend on the thermal transmittance (the U-value) and the total solar energy transmittance (the g-value). This fact makes it difficult to choose the glazings or windows with respect to energy performance in a given case. To compare different glazings or windows in an easy way, diagrams have been produced which give the net energy gain based on the orientation, the tilt, the U-value and the g-value of the glazings or windows. In addition, a single diagram showing the net energy gain in a one-family house has been produced which takes into account the orientation of the windows in the building. This makes it possible to evaluate the energy performance of different glazings or windows for a one-family house using a single diagram. The diagrams give an easy way of comparing different glazings or windows so the best solution in a given case can be chosen. In addition, the diagram showing the net energy gain in a one-family house is used in the Danish Energy Labelling and Rating system for classification of glazings.