Thermal stress breakage typically occurs when the temperature difference between the edges and the center of the glass reaches a critical point. Most frequently, thermal breakage occurs when the edges of the glass are cold and the center becomes heated. This condition is most common in buildings with overhangs and deep vertical mullions. It should also be noted that tinted, coated, and reflective glass products are the most susceptible to thermal stress breakage.
Thermal stress breakage is especially a concern during construction when the interior of the building is unheated and installed glass is exposed to direct sunlight. In such cases, breakage occurs when the central part of the glass becomes heated by the sun and the edges are cooled by the frame. Another common cause of thermal stress breakage is when blinds are installed to closely to the interior glass surface trapping warm air created by either the heating system or by the sun in close to the glass. Please see the shading device section for more information.
Solar Seal Company is pleased to assist with thermal stress calculations to help determine if heat treating may be necessary. However the selection of product type and the prevention of thermal stress breakage is the responsibility of the design professional. For more information please see the Pilkington Thermal Stress Calculator or the PPG Thermal Stress Calculator.