Glossary

Visible Light Transmitted (VLT)

The 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)

The percentage of visible light reflected by a glazing system can be seen visually.

Total Solar Energy Transmitted

The 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

The ratio of the total solar energy directly reflected by the glazing system to total solar energy falling on it.

Total Solar Energy Absorbed

The ratio of the total solar energy directly absorbed by the glazing system to total solar energy falling on it.

Ultraviolet Light Transmitted

The 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 Co-Efficient

The ratio of the solar heat gains 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 components; ultraviolet, visible and near-infrared. All three cause heat when solar radiation is absorbed.

Tinted Glass

Glass which is coloured using minerals; generally less effective than glass coated with film.

Non-Reflective

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 Film

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.