Energy terms


Measures the resistance of heat transfer through the glass. The higher the R-value, the better the mechanical performance of the window. R-Value is not typically used as a measurement.

Shading Coefficient.

Shadindg Coefficient is the ratio of solar heat gain through a specific type of glass that is related to 1/8 inch clear glass. When the shading coefficient number decreases, heat gain is reduced, reulting in better performing product..


A measure of heat gain or heat loss through the glass due to different temperatures, indoor and outdoor. Reciprocal of K-Value, a lower U-Value indicates better insulating properties.

Visible Light Transmission.

The percentage of light that is transmitted through the glass.

Argon Gas.

A none toxic gas, used between to lites of glass, typically used in 3M.clr/Air Space/3M Low-E to enhance the mechanical performance of the insulated unit. Reduces STC (sound transmission), an Energy Star requirement..