Search our window construction terminology page and explore glossary terms related to energy efficiency and performance. The following is 1 of 4 pages on our section dealing with window terminology. For a visual, refer to our anatomy of a window.
Bill — Site Editor
Window Construction Terminology
Air Infiltration
Ahe amount of air that leaks through the edges of a frame when it is closed. This calculation is represented as cfm/sf or cfm/sq ft, which translates to ‘cubic feet per minute per square foot’. Specifically, the lower the AI, the better.
Condensation Resistance Factor (CRF)
An indicator of how resistant a window is to condensation. Specifically, the higher the number, the better resistance.
Conduction
Conduction is the amount of energy transferred between materials in direct contact with one another.
Convection
The amount of energy that is transferred by air circulation between surfaces.
Energy Star®
The government created the Energy Star system to help consumers determine which products provide more energy efficiency.
Heat Absorbing Glass
Glass that is tinted in order to absorb heat and light and reduce glare. Learn more on replacement glass.
Low-E Glass
Also known as low emittance glass, it is glass which has a specialized coating to reduce radiant heat gain and create better energy efficiency.
Additional Window Construction Terminology
National Fenestration Rating Council® (NFRC)
An organization that certifies energy ratings for windows, doors and skylights.
R-Value
An indicator of a window’s insulating properties and resistance to heat transfer. Specifically, the higher the value, the better it is at insulating against heat transfer. This value is the inverse of the U-factor.
Radiation
The heat producing spectrum of the rays of the sun.
Reflective Glass
Coated glass that can reflect the heat and light of the sun, reducing the amount of heat transfer and glare.
U-Factor
An important replacement windows ratings that indicates a window’s heat transmission (indicative of energy efficiency). The lower the U-factor, the better the insulative properties of the window. This value is the inverse of the R-value. Specifically, the lower the number, the better.
Ultraviolet Light
The short wavelengths of light that can cause fading.
Visible Transmittance
VT – a measurement of the percent of visible light that penetrates through a window. Specifically, the higher the VT, the better/
Warm-Edge Technology
The use of spacers that have low conductive properties near the edge of insulated panes of glass. This further reduces the amount of heat transfer and increases energy efficiency.
Wind Load
The measurement of force caused by moving air against a surface.
Related Topics
Components Terminology
Frame Terminology
Installation Terminology
