Understanding the Cause of Thermal Stress Breaks in Glazing Systems

Robert Quintal from our Survey & Investigation team recently attended site to observe the replacement of an Insulated Glass Unit (IGU) and investigate a fracture within an internal glass pane.

A close inspection of the fracture pattern identified several indicators consistent with a thermal stress break, including:

• A crack originating from the glass edge before travelling perpendicular and branching
• Stress patterns around the origin, suggesting a potential edge flaw or micro-crack
• A fracture likely triggered by significant temperature differences between the centre of the vision pane and the edge concealed behind black structural silicone

The investigation also raised further considerations, including whether alternative stress patterns could indicate a trapped air bubble or inclusion from the manufacturing process. A small, dislodged piece of glass may also suggest another possible fracture mechanism, rather than a simple edge flaw alone.

Cases like this demonstrate how critical edge quality, installation conditions, and thermal exposure are to glass performance. Even the smallest imperfection can become a significant point of failure under the right conditions.

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