1. Insulating glass units and solar radiation

The solar radiation to which glazing is exposed is made up of ultraviolet, visible and near-infrared rays. The components of this radiation are shown in figure 1 as a function of wavelength.

This radiation is partly reflected, partly transmitted and partly absorbed by the glass, as shown in figure 2 .

The transmission, reflection and absorption factors, by wavelength, are the ratios of these different fluxes to the incident flux.

In the case of insulating glass units, we have to take into account multiple reflections in the direction of radiation, and vice versa. In practice, we consider only the first external and internal reflections of each...