The influence of windows on the energy consumption in buildings is well known and in order to encourage the development and the appropriate use of high performance glazings and windows in Denmark, an Energy Labelling and Rating system is being developed. During this work a need for establishing a common and well-defined method to characterise the performance of glazings and windows on the Danish market has been recognised. This paper gives a short description of the Danish energy labelling and rating system for glazings and windows, which was put into operation during 2000. Furthermore, the results of a comparison between measured and calculated thermal transmittance for five different window types are given. The calculations on the glazing part have been performed in five different programmes (WIS, WINDOW, VISION, CALUMEN and GLAD99). The calculations on the frame part have been performed in three different programmes (FRAME, THERM and WinIso). The comparison indicates that all investigated programmes are qualified for calculating energy labelling data for glazings and windows. (C) 2002 Published by Elsevier Science Ltd.