Glossary

Visible Light Transmitted (VLT):     Ratio of visible solar energy (380-750nm) that passes through the glazing system to the total visible light falling on it.

Visible Light Reflectance (VLR):      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 on 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 3 mm thick) under the same test conditions. Lower the shading coefficient number, better the Sun Control capability.

Solar Energy Spectrum:                        Solar radiation has three component; 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 (HP):           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.