With the drive towards energy efficiency, many consumers are making their homes as energy efficient as possible. As this demand for energy efficient products has increased, the energy code requirements have become tougher on manufacturers. Specifically, glass manufacturers have evolved, and continue to evolve, their glass making processes. A recent article by Katy Devlin in Glass Magazine lays out the past, present, and future of energy efficient – high performance glass. From the consumer perspective, this article is very informative and worth the read. Particularly if you are currently or will be in the future looking to make your home more energy efficient. Click HERE to read the full article. The following is some useful information when reading about energy efficiency:

The Terminology of Energy-efficient Glass

U-FACTOR (U-VALUE):
The measure of the rate of non-solar heat loss or gain through a window system in terms of Btu/hr.-sq. ft.-ºF. The lower the U-factor, the greater the resistance to heat flow, meaning a better insulation.

R-VALUE:
The measure of the resistance of a glazing material or fenestration assembly to heat flow. The inverse of the U-factor or R = 1/U.

SOLAR HEAT GAIN COEFFICIENT (SHGC):
The fraction of the solar radiation admitted through a window or skylight both transmitted and absorbed, and released inward.

VISIBLE TRANSMITTANCE (VT):
A fraction of the visible light spectrum transmitted through glazing. The higher the VT, the more visible light transmittance.

LIGHT-TO-SOLAR GAIN (LSG):
The ratio between theW SHGC and VT. A gauge of the relative efficiency of glazing in transmitting daylight while blocking heat gains. The higher the number, the more light transmitted without adding excessive amounts of heat.

SOURCES: Bill Lingnell, technical director,Insulating Glass Manufacturers Alliance (U-value, R-value and SHGC). U.S. Department of Energy (VT and LSG).