Ratings for individual window series are as follows:
Starline Architectural Windows tests all capabilities of its windows, including thermal factors, such as the:
Rate of heat flow through the complete heat barrier, from room air to outside air. The lower the U-factor, the better the insulating value. The U-value is the reciprocal of the R-value.
The SHGC is a rating which is now generally replacing the shading coefficient, measuring a window's ability to transmit solar heat. It measures both the solar radiation which is directly transmitted, as well as the solar radiation absorbed by the glass and subsequently transmitted. The lower a unit's solar heat gain coefficient, the less solar heat it transmits, and the greater is its shading ability. The solar heat gain coefficient is approximately equal to the shading coefficient divided by '1.15' and is expressed as a number without units between 0 and 1.
A fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through a window's, door's, or skylight's glazing. A product with a higher VT transmits more visible light. VT is expressed as a number between 0 and 1.