When glass is subjected to the effects of solar radiation, the immediate result is an increase in the temperature of the glass. Depending upon shading and support conditions, the influx of solar radiation can lead to significant variations in temperature across the surface of the glass. Variations in glass surface temperature lead to the introduction of thermally induced stresses.
The level of solar exposure depends to a large extent on orientation of the glass. North facing glass receives the least amount of solar exposure and as a result thermal fractures associated with Northerly facing glass tend to be rare. All other exposures tend to experience sufficient solar insulation to experience significant thermally induced stresses. Glass that has a Southerly exposure tends to experience the most dramatic overall heat build up during the course of a day. Depending upon the conditions associated with the installation, thermal fractures can be expected on glass with southerly exposure.
Glass that faces toward the East has the possibility of experiencing the early morning effects of solar exposure. Such exposure can be extremely critical during winter months when glass that has had several hours to reach a very low uniform temperature on a cold winter night is suddenly subjected to a blast of early morning sunlight. This situation often leads to thermal fracture if the conditions associated with the glass are conducive to glass failure. West facing glass is subjected to the afternoon affects of the sunlight which depending upon conditions of the installation can lead to similar significant thermal stresses.
Therefore, it is important to note the exposure (N, NE, E, etc.) of each glass plate. The possibility for thermal fracture can usually be discounted for glass plates with NW, N, or NE exposures in the northern hemisphere and the SE, S, or SW exposures in the southern hemisphere. However, it must be considered for all other exposures.
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