Solar Factor

Solar Factor (FS) is the percentage of solar energy incident on the glass that is transferred indoors both directly and indirectly through the glass.

The direct gain portion equals the solar energy transmittance, while the indirect is the fraction of solar incident on the glass that is absorbed and re-radiated or convected indoors. For example, 1/8" (3.1 mm) uncoated clear glass has a FS of approximately 0.86, of which 0.84 is direct gain (solar transmittance) and 0.02 is indirect gain (convection/re-radiation).