Glass Glossary

Heat-Strengthened Glass


Last Updated: November 23, 2023

Heat-strengthened glass is a type of thermally treated glass that has been specially processed to enhance its strength and resistance to windload and thermal stress. It is approximately two times stronger than annealed glass of the same thickness in resisting windload.

In the event of breakage, heat-strengthened glass typically fractures into large sections, akin to annealed glass, and usually remains in place within the opening. This feature makes it a preferable choice for applications where safety requirements are not paramount.

Heat-strengthened glass is ideal for scenarios where annealed glass does not meet thermal or windload requirements. It is suitable for all tinted, LoĒ™ and reflective vision applications and is the recommended choice for spandrel applications, meeting all necessary requirements, codes, and specifications for strength and durability.

Heat-Strengthened vs. Tempered Glass

Heat-strengthened glass and tempered glass are both thermally treated to enhance their strength, but they differ in several aspects:

  1. Strength: Heat-strengthened glass is about twice as strong as annealed glass in resisting windload, whereas tempered glass is approximately four times stronger.
  2. Breakage Pattern: Heat-strengthened glass breaks into large sections similar to annealed glass, usually remaining in the opening. Tempered glass, however, shatters into small, less hazardous fragments.
  3. Thermal Treatment: The thermal treatment for tempered glass involves heating it to higher temperatures and cooling it more rapidly than heat-strengthened glass, resulting in greater surface compression and strength allowing it to meet requirements for safety glazing such as doors.