Visible Light Transmission (VLT) |
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Infra-red Rejection (IR) |
| The percent of total visible light that passes through a glazing system. |
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The percent of total heat that is rejected from passing through a glazing system. |
Visible Light Reflectance (VLR) |
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Total Solar Energy Rejected |
The percent of total visible light that is reflected by a glazing system.
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The percent of incident solar energy (heat) rejected by a glazing system which equals solar reflectance plus the part of solar absorption which is re-radiated outward.
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Ultra-violet Rejection (UV) |
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Luminous Efficacy |
The percent of total ultra-violet light that is rejected from passing through a glazing system.
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The ratio of daylight transmission to solar heat transmission which passes through a glazing system. This is determined by dividing the visible light transmission by the shading coefficient. The higher this number the better it indicates how much of the transmitted solar energy is useful visible light rather than heat |
Shading Coefficient |
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Value |
| The ratio of solar heat gain through a glazing system to the solar heat gain of a single lite double-strength glass. A measure of degree of efficiency of a glazing system to control solar energy. The lower the shading coefficient, the better the solar shading quality of the glazing system. |
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The overall coefficient of heat transfer by conduction equals the reciprocal of R value. The lower the U-Value, the better the insulating qualities of the glazing system.
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Emissivity |
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A measure of the ability of a product to reflect long wave radiant energy. The lower the emissivity, the better the insulating quality of the glazing system.
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