Building with glass, aluminum, and ideas.
TECHNICAL BINDER: Guide to Glazing, Finish Options and Performance
Glass Types: An Overview
When analyzing and selecting a glass type, it is important to compare the optical and thermal properties of each type of glass and select the one that best matches your specific performance requirements.
Glazing is one of the most important factors to consider when designing a skylight or curtain wall project. AGT recommends using only real glass in lieu of translucent, acrylic panels. Glass provides superior thermal and optical properties, won't yellow or fade, and is much less susceptible to leakage after extended exposure to the harsh effects of an outdoor environment.
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Laminated Glass
Laminated glass, often called "safety glass", consist of two lites of equal thickness (usually ¼”) bonded together with a plastic interlayer consisting of polyvinyl butyral (P.V.B.). In the event that the glass should break, the P.V.B. interlayer will allow the glass to remain in the skylight framing. Colored PVB's which allow a virtually unlimited range of color are incorporated in many skylights.
Three excellent examples of what is possible by incorporating colored glass into a design are:
Insulated Glass
Insulated glass consists of a ¼" thick, heat-strengthened outer lite, over a ½" dual sealed airspace, over a heat strengthened, laminated inner lite (thickness to be determined based on size of lite). Because of its inherent thermal properties, insulated glass is typically used over a conditioned space, where energy efficiency is of paramount concern.
Annealed Glass
Annealed glass is non-tempered glass which can easily be fabricated and cut to size. Annealing is the process of slowly cooling the glass under controlled conditions when it is being manufactured. Annealed glass is rarely used in sloped glazing.
Tempered Glass
Tempered glass is produced by heating annealed glass to approximately 1150 degree F, then cooling the glass rapidly by blowing air on both surfaces of the glass simultaneously. Tempered glass is approximately four times as strong as annealed glass of the same size and thickness. When tempered glass is broken, it breaks into very small pieces. One problem that exists with tempered glass is spontaneous breakage, where the glass can break for no apparent reason. Spontaneous breakage occurs when nickel sulfide stones increase in size due to repeated heating and cooling.
Heat Strengthened Glass
The heat strengthened glass production process is similar to that of tempered glass. Annealed glass is heated to approximately 1100 degrees F, but the cooling process is slower than that for tempered glass. Heat strengthened glass is about twice as strong as annealed glass of the same size and thickness. One of the benefits of heat strengthened glass is that it is far less susceptible to spontaneous breakage.
Due to this, Architectural Glazing Technology recommends the use of heat strengthened glass for skylights. This is an important point of differentiation, when comparing the quality of skylights.
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Please contact us or call us at 800-345-7899 for more information about the right type of glass to use in your next project.