Thermal breakage can be influenced by a number of factors. There are many factors to be considered in the early stages of glass selection that can influence the thermal stress in the finished product.
One element to be considered is whether the glass will be shaded. When glass is partially shaded by building overhangs or extensions, it becomes cooler in those areas and stress in the glass may occur, which can result in thermal breakage. The degree to which the central area of the glass becomes hot is largely dependent on the solar absorption of the glass, which varies between different types of glass.
In areas where thermal breakage may be of concern, a thermal stress analysis must be completed to determine if heat treatment (heat-strengthening or tempering) may be needed.
Some additional factors that may influence thermal breakage are listed below:
- Highly conductive glass framing or framing that is in direct contact with concrete or other materials that may contribute to the cooling of the glass edge
- Excessive coverage of the glass edge by the frame
- Heat absorbent film attached to the glass after installation
- The use of internal shading devices such as curtains, drapes or venetian blinds increases the thermal stress and should be validated with a thermal analysis.
- The airflow from room cooling or heating vents must be directed away from the glass
- Buildings not heated during the construction phase may experience an increase in thermal breakage
Glass may also be subject to thermal stress during on site storage, prior to be glazed. Care should be taken to store glass in a clean dry environment which is not in direct sunlight.
The potential risk of thermal breakage can be estimated by a computer aided thermal stress analysis. Contact your Guardian representative or local technical department for assistance.