Glazing Terminology
Annealed Glass
Basic form of float glass. Annealing is the process of a controlled cooling done in a lehr to prevent residual stresses in the glass. (SSB: single strength 5/32" / DSB: double strength 1/8")
Tempered Glass
The higher compression levels usually yield a product that is generally four times
stronger than the annealed glass. When broken by impact, fully tempered glass
immediately disintegrates into relatively small pieces thereby reducing the likelihood of serious cutting or piercing injuries
Low Emissive (Low-E) Coated Glass
Low-E coated glass has quickly become the standard type of glass in replacement windows to help combat high energy costs. During the wintertime, Low-E Glass transmits the sun's visible light and directs solar shortwave infrared energy into the home. At the same time, its reflect longs wave infrared (heat) energy -- like that which comes from a home's heating system -- back into the room, helping to keep homes warmer. Its also keeps the room side glass surface of a window warmer than uncoated glass, helping to eliminate that drafty feeling near windows and sliding glass doors. Low E glass reduces formation of condensation on the interior perimeter of the glass surface, which can damage the window sash. Because Low E glass also reduces relative heat gain, windows made with this glass help keep homes cooler in summer, too. The result is year-round energy efficiency and comfort. (Low E2 Solarban 60: darker metallic film (green tint)/ Low E hardcoat (yellow tint): lighter metallic film)
Insulated Glass Units
Insulating glass units are made of two or more lites of glass hermetically sealed at the edges with an air or gas filled space between them. The air space is usually ?? or ??, but can be varied on large orders. The lites are separated by a spacer around the entire perimeter. The space contains a moisture-absorbent material called a desiccant that serves to keep the enclosed air free of visible moisture. The entire perimeter of the assembly is sealed with materials to resist moisture vapor transmittance and to structurally bond the components together.
Spandrel Glass
Spandrel glass panels are heat-strengthened or fully tempered glasses with either a colored ceramic frit permanently fused to one of the surfaces or a solar control/reflective coating.
Laminated Glass
Laminated glass materials used today are fabricated in one of the following methods: Sandwiching an interlayer of clear or tinted polyvinyl butyral (PVB) between two or more lites of glass and permanently bonding them together under heat and pressure.
Safety Glass
Glass materials designed to reduce the possibility of bodily injury from glass shards upon breakage. The two glass types considered safety glass are fully tempered and laminated glass. State law requires that any piece of glass less than 18" from the floor to the bottom of the glass or a piece of glass that is less than 24" away from a door opening be some form of safety glass
Fire Rated Glass
Fire rated glass products are tested and certified as components of a complete system. The use of fire rated glass alone does not qualify the entire glazing assembly as fire rated. Fire ratings vary from 20 minutes through 3 hours. Size limitations may apply from building code restrictions. Wired glass is a commonly used fire rated glass. (Baroque Wire: square pattern, Misco Wire: diamond pattern)
Solar Energy Reflectance: In the solar spectrum, the percentage of solar energy that is reflected from the glass surface(s).
U-Value: A measure of air-to-air heat transmission (loss or gain) due to the thermal conductance and the difference in the indoor and outdoor temperatures. As the U-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-value, the more restrictive the fenestration product is to heat transfer; the reciprocal of R-value.
R-Value: The thermal resistance of a glazing system expressed ft?/hr/?F/Btu (m?/W/?C). The R-value is the reciprocal of the U-value. The higher the R-value, the less heat is transmitted throughout the glazing material.
Visible Light Reflectance: The percentage of visible light (390 to 770 nanometers) within the solar spectrum that is reflected from the glass surface.
Visible Light Transmittance: The percentage of visible light (390 to 770 nanometers) within the solar spectrum that is transmitted though glass.
