Window installations have a considerable impact on the heating energy consumption of Passive Houses. The differences in heating demand may be in the region of 1 kWh/(m²a). While estimating the thermal bridge coefficient of installations is inaccurate, it takes too long to calculate it accurately during the planning stage. This is because doing so requires the precise geometries of the frames as well as all their material properties to be researched.

This is presumably why projects are regularly found to have unsuitable, simplified thermal bridge calculations, in which a panel and its Uw value are used as opposed to the window itself. This calculation is completely meaningless! When this method is applied, the results depend on the choice of glazing. In reality, however, glazing has no influence on the installation position. To help overcome this obstacle to the proper planning of energy-efficient window connections, this report investigates a simplified model for various frame types and compares the calculations with those made using models with precise frame geometries.