5.3Total Solar Energy Transmittance (Solar Heat Gain Coefficient)

5.3.1 Solar heat gain coefficient (SHGC)/solar factor (SF) is the measure of amount of heat transfer from outside to inside by direct transmission (Short Wave Radiation) and internal remitted radiation (Long Wave Radiation). The SHGC (see Fig. 6) or SF depends on the tint of the substrate and also the type of coating that is done on the base glass. The amount of solar energy gained through glass is between 0 and 1. Multiplying the SHGC or SF by 100 gives the percentage of solar energy allowed into the building.

The total solar energy transmittance $g$ is the sum of the solar direct transmittance $\tau_{\mathrm{e}}$ and the secondary heat transfer factor $q_{\mathrm{i}}$ towards the inside, the latter resulting from heat transfer by convection and long-wave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing and is expressed as: