As the link between the building and its external environment, the façade is highly significant for the design of the building. Furthermore, it plays a decisive role with regard to energy flows and other interactions between the interior and exterior of the building. The demands imposed on the facade thus arise from a variety of technical functions. In particular, the interactions among these technical functions are very important and compel an integral perspective.

With regard to climatic conditions present during the summer months, limiting solar thermal heat gain via the transparent areas of the façade is a key consideration. Here it is recommended to analyse the shading situation as the first step, in order to determine whether a shading system is necessary. Such an analysis may also be relevant with regard to planning permission and building regulations.

The amount of solar heat gain via a transparent façade exposed to intense solar radiation depends on the choice of glazing materials and the shading system.

The shading quality of a façade is expressed in terms of its solar heat gain coefficient (shading factor). Although an initial, rough value for this coefficient can be approximately estimated using the solar heat gain coefficient of the glazing and the attenuation factor of the shading system, such an rough estimate cannot take system-specific properties into account, such as high levels of reflection from specular elements of the shading system. Significantly better results can be obtained by computational calculations, which base on the physics of energy radiation and the spectral distributions of transmission, reflection and absorption for each of the façade´s individual layers (i.e. glass panes and/or shading system) and which deliver reliable values for the specific facade ´s properties of the particular project.

These calculations can also provide information about the temperature profile within the glass façade under conditions of intensive solar radiation.