Definition: | ratio of the quantity of heat penetrating into an interior through the glazing, to the solar radiant energy incident on that glazing
NOTE – This ratio is the sum of two quantities : the radiant transmittance τe of the glazing and the quantity equal to the ratio of the convected and radiated heat gain from the glazing into the interior Q2 to the solar radiant energy Q1 incident on the glazing
g = τe + Q2/Q1.
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