Glossary of Technical Terms

Visible Light Transmitted Ratio of visible solar energy (380-750nm) that passes through the glazing system to the total visible light falling on it.
Visible Light Reflectance Percentage of visible light reflected by a glazing system that can be seen visually.
Total Solar Energy Transmitted Ratio of the total solar energy passing through a glazing system to the amount of total solar energy falling on it.
Total Solar Energy Reflected Ratio of the total solar energy directly reflected by the glazing system to total solar energy falling on it.
Total Solar Energy Absorbed Ratio of the total solar energy directly absorbed by the glazing system to total solar energy falling it.
Ultraviolet light transmitted Ratio of solar energy (wavelength: 300-380nm) that’s transmitted by a glazing system to the total solar ultraviolet energy falling on it. Note: UV energy is not visible to the human eye; it causes the degradation and de-coloration of organic matter, upholstery etc.
Total Solar Energy Sum of energy transmitted, reflected and absorbed by the glazing system.
Total energy rejected Percentage of incident solar energy rejected by a glazing system. This includes solar reflectance and a part of solar absorption that is re-radiated outward.
‘U’ Factor This is the rate of heat conductivity of a glazing system. It is independent of solar radiation. When multiplied by the difference between indoor and outdoor temperature in Fahrenheit, it gives the amount of heat in BTUs/ hours/ square foot of glazing. Greater the temperature difference, higher the U factor, so it’s important to observe closely the U factors that represent your conditions
Shading Coefficient Ratio of the solar heat gain through a given glazing system to that of a standard pane glass (1/8 inch or 3mm thick) under the same test conditions. Lower the shading coefficient number, better the Suncontrol capability.
Solar Energy Spectrum Solar radiation has three components: ultraviolet, visible and near-infrared. All three cause heat when the solar radiation is absorbed.
Tinted Glass Glass which is coloured using minerals; generally less-effective than glass coated with film.
Non-Reflective Films These are impregnated with dyes to offer sun protection. Non-reflective films absorb the sun’s energy and light, and are ideal for automobiles
Reflective Films These are coated with a micro-thin, partially transparent layer of metal, and have a mirror-like finish. They generally work by reflecting light, rather than absorbing it, and are excellent for buildings.
High-Performance Film This is a double ply, 37 microns thick dyed film with a metallic sheen which has been specially developed to provide higher heat rejection without compromising on light transmission.

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