Glazing Energy Terms:
(Please refer to these terms when comparing performance levels)
| Visible Light Transmittance: | The percentage of visible light that is transmitted through the glass. Interior daylight levels will be determined by this value. The higher the percentage, the more daylight is transmitted. |
| Solar Transmittance: | The percentage of ultraviolet, visible and near infrared energy that is transmitted through the glass. |
| Visible Light Reflectance: | The percentage of light that is reflected from the glass surface. |
| Solar Reflectance: | The percentage of solar energy that is reflected from the glass surface. |
| ASHRAE U-Value: | The amount of heat gain or loss through glass due to the difference between indoor and outdoor temperatures (based upon ASHRAE standard winter nighttime and summer daytime conditions). The colder the climate, and the more expensive the heating fuel, the more important it is to utilize a low U-value glass. |
| Shading Coefficient: | The ratio of solar heat gain through a specific type of glass product to the solar heat gain of a 1/8" (3mm) clear glass. The lower the shading coefficient number, the better the performance of the glass. This is particularly important in warmer climates. |
| Relative Heat Gain: | The amount of heat gain relative to the effects of the solar heat gain (shading coefficient) and conductive heat gain (U-Value) of the glass. The lower the relative heat gain value, the more efficient the glass is in restricting heat gain. |
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