Thermal / Solar Stress to Glass

Can glass break if graphics or film is applied to the glazing?

Glass is always prone to breakage whether or not it has an application installed to it. However, the chances of this happening is very low if the glass complies with the correct standards and is in good condition.

Thermal stress is caused by a difference in temperature in one part of the glass. More stress is caused as the temperature difference increases. The following diagrams show the process of thermal stress breakage.

Bonwyke Design - Solar energy warming glass
Figure 1. The centre of the glass rises in temperature due to solar energy. The glass edges remain cool due to being hidden by the frame.


Bonwyke Design - glass expanding diagram
Figure 2. As the centre of the glass expands, the cooler edge of the glass is under stress to expand with it.


Bonwyke Design - exceeding breaking strength
Figure 3. When the glass exceeds the breaking strength of the glass, thermal stress fracture will occur.


Toughened glass should never suffer from excess thermal stress due to the manufacturing process except when exposed to fire.

Heat strengthened glass is also likely never to suffer from thermal stress due to its manufacturing process.

Annealed glass on the other hand, should be treated with more care as it constructed differently to toughened and heat strengthened glass.

Factor to consider when avoiding thermal stress.

Specifying the correct window film is one of the first steps to take when trying to minimise the chances of glass breakage. Other factors involved are:

  • Glass quality
  • Glass thickness
  • Glazing type
  • Glass specification
  • External / Internal shading
  • Frame type
  • Altitude
  • Solar energy intensity

Glass condition and official standards should be given particular attention. Incorrect glass specification can increase the risk of breakage to glass. Solar energy transmission, absorption and reflection are factors to consider when choosing the correct material for glass application.

Bonwyke Design carry out thermal stress compatibility assessments which are highly recommended if you are unsure on your glass specification. For more information or advice, please contact us.