Thermal Stress Breakage

Thermal stress in glass is usually caused by the temperature differences between the covered edges and the center portion of the glass. Thermal stress in the glass increases as the center-of-glass and edge temperature differences increase. The probability for glass breakage increases as the thermal stress increases.

It is advisable to perform a project-specific thermal stress analysis for each project where thermal stress breakage is a concern. Many factors, besides the glass type, must be considered in a thermal stress analysis. These include, but are not limited to, the window frame material and color; glass shading from overhangs and balconies that create unusual shading patterns across the glass surfaces; blinds and window treatments; air and heating vents; blowing on the glass; glass size; as well as the direction and elevation of the sun.

Thermal stress breakage of annealed glass will occur when the thermal stress exceeds the glass edge strength. Tempering or heat-strengthening will normally prevent glass breakage due to thermal stress.

The more heat-absorbing the glass is, the higher the thermal stress will be. Tints and reflective glasses have higher solar absorption and are therefore more susceptible to thermal stress breakage.