When examining a window system, it is important to review and determine the condition of the glazing materials. This should be from the interior and exterior of the building. When the glazing materials are not functioning adequately or have failed, the possibilities of thermal stress fracture and/or seal failure of insulating glass are drastically increased. The site inspection should include close examination to see if the glazing gaskets, sealants or tapes are of the type that are shown on the drawings or as called out in specifications. When written documentation is not available, the glazing materials should still be carefully observed to determine if deterioration or lack of functionality is occurring. When sealants have lost adhesion to joining material or show splitting and cracking, most likely the material is not doing the specified job anymore. This can allow water into the frame or cause loss of thermal isolation.
Gaskets and tapes can be disengaged or squeezed out of the original position. This can cause glass-to-metal contact and allow a metal frame to be in direct contact with glass which will worsen thermal stress conditions.
Check the dimensional thickness of the glazing material around the perimeter of the frame for uniformity. Inconsistent glazing material will lead to conditions of inadequate support, poor thermal isolation and can allow air and water infiltration. Be aware that when the glazing materials fail it can usually lead to other problems that either impact the glass performance immediately or in due time.
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