DEFINITION OF ENERGY TERMS U-VALUE A measure of the heat gain or loss through glass due to the difference between indoor and outdoor air temperatures. It is also referred to as the overall coefficient of heat transfer. The lower the U-Values, the better the insulating properties. The units are Btu/(hr)(ft2)(°F). SHADING COEFFICIENT (SC) A measure of the heat gain through glass from solar radiation. Specifically, the shading coefficient is the ratio between the solar heat gain for a particular type of glass and that of double-strength clear glass. The lower the shading coefficient, the lower the solar heat gain. SHORT AND LONG WAVE SHADING COEFFICIENT Shading Coefficient can be broken up into two components known as long and short wave shading coefficients. Short wave shading coefficient represents the percentage of solar transmission in the range of 300 to 4,000 nanometers. (Short Wave S.C. = Direct Solar Transmission x 1.16). Long wave shading coefficient represents the percentage of solar transmission in a range of 4,000 to 50,000 nanometers. (Long Wave S.C. = Shading Coefficient - Short Wave Shading Coefficient). Short wave and long wave shading coefficients are terms which are commonly referenced in Europe and are gaining popularity in other parts of the world.

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