|A guide to glass selection|
|Due to technological improvements achieved in the last 30 years, glass has become an important building material. More and more building surfaces are covered with glass. Accordingly, a correct selection of glass type is crucial.|
|When selecting the type of glass used for buildings a number of different characteristics should be evaluated. Here are some of the glass properties to consider:
Solar energy can be pleasant and utilisable in many cases, but especially in buildings, it represents a major source of overheating and unpleasant glare. Solar control glass, usually either body-tinted (absorbing) or coated (reflecting), is used to reduce unwanted solar radiant light and heat energy transmitted through glass. The Solar Heat Gain Coefficient (SHGC) is the best measure to determine how well a product blocks heat caused by sunlight. A similar, but much less precise measure of heat gain, is the Shading Coefficient (SC).
The need to restrict sound arriving from the external environment means that glass should be able to shield and insulate the internal spaces of a building. Glass type is the major factor influencing the passage of sound. The most common types of glass used are laminated and insulating glass (Double glazed). Laminated glass incorporates a special acoustic PVB interlayer, which absorbs some of the incident sound energy, reducing its passage. Better sound insulation can also be achieved with double-glazed glass in which vacuum-sealed inner spaces and some gases affect sound insulation and provide acoustic stability.
The U value is a measure of the rate of heat loss of a building component. It is expressed as watts per square metre, per degree Kelvin, W/m2K. Lower U-Values are achieved by multiple glazing layers, gases and the use of low-e coatings.
Glass is subjected to different types of environmental and human loads, which can cause glazed surfaces to malfunction or break. Since each load has a specific impact on glass, with different calculation formulas, it is important to understand each of these phenomena in order to choose the appropriate glass.
When we talk about visual appearance we have in mind the color of glass surface. Thanks to the latest manufacturing processes, glass can be made available in several colors. When we combine single sheets of glass in laminated or insulated units, they typically change in overall color and appearance. Glass color appearance can be also conditioned by several environmental factors such as sunlight (midday sun or sunset), reflected sky and clouds, etc.
Last review: October, 2012
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