Performance Glass Terminology

  • VISIBLE LIGHT TRANSMISSION

This figure indicates the amount of light passes through the sample pane of glass

  • VISIBLE LIGHT REFLECTION

This figure indicates the amount of light that is reflected away from surface of the sample pane of glass.

  • SOLAR ENERGY (HEAT)

All energy received from the sun on the surface of the earth. This includes the energy from the ultraviolet, visible and infrared segments of the solar spectrum. For reasons of standardization solar energy is measured between the wavelengths 280nm to 2500nm.

  • SOLAR ENERGY TOTAL ELIMINATION

The part of the sun’s energy stopped by glass or the glazing system. The effectiveness varies in accordance with environmental conditions. In warm climates, glazing systems are compared using the American Society for Heating, Refrigeration and Air-conditions. The environmental conditions, which affect solar heat elimination, include air speed against both surfaces of the glass, and temperature (also on both of the glass).

  • SOLAR ENERGY REFLECTION

This figure indicates the amount of Solar Energy (heat) that is reflected away from the surface of the sample pane of glass. The part of the sun’s energy which is reflected by the glass or glazing system. This is independent of environmental conditions.

  • SOLAR ENERGY ABSORPTION

The higher the absorption the higher the thermal stress and the more likely the glass will crack if incorrectly glazed.

  • SOLAR ENERGY DIRECT TRANSMISSION

The part of the sun’s energy which passes directly through the glass. This is independent of the environmental conditions.

  • S.H.G.C. (Solar Heat Gain Co-efficient)

This figure is obtained by dividing the total solar transmission by 100, to factorize it e.g. a glass having a total solar transmission of 50% will have an S.H.G.C. of 0.50 (50/100 = 0.50)

  • SHADING CO-EFFICIENT

This figure is a function of the Total Solar Energy (Heat) transmitted through the sample pane of glass as compared to the Total Solar Energy (Heat) transmitted through a 3mm thick pane of glass. The lower the figure the better the performance.

  • U-VALUE

This figure indicates the amount of energy (measured in Watts) that is lost through 1m² of the sample pane of glass for every degree of temperature difference between outside and the inside ambient air. The lower the U-value the better the performance.

  • THERMAL STRESS EVALUATION

It is recommended that a thermal stress evaluation is done on laminated safety glass with a high heat absorption, prior to installation.