What is the thermal conductivity of glass?

The thermal conductivity of glass is a key consideration when designing and constructing sustainable buildings. Find out more in our guide.



Thermal conductivity is a physical property of all materials. It measures how easily heat flows through a material. Represented in equations by the symbol k, it's measured in watts per metre-kelvin (W/mK).

High-conductivity materials like copper and aluminium transfer heat quickly, while low-conductivity materials like foam and fibreglass transfer it slowly.

Thermal conductivity is an important factor when considering how materials behave. In the case of glass, it contributes to the overall thermal efficiency of a building.

This is because not all glass products are made equal. If you buy low-performance glass for a building project, you're likely to oversee a project with poor thermal efficiency. This can have negative effects on compliance and user comfort.

What is the thermal conductivity of glass?

Glass has a relatively low level of thermal conductivity. It varies from type to type, but generally falls between 0.5 and 1.4 W/mK.

Most of the glass we interact with in daily life, whether in windows or glassware, has a thermal conductivity of between 0.9 and 1.2 W/mK.

To put that in perspective, copper has a thermal conductivity of 401 W/mK, while foam glass is a mere 0.045 W/mK.

What is the thermal conductivity of toughened glass?

The thermal conductivity of toughened (tempered) glass is around 1.1 W/mK. This is similar to standard annealed glass. That's because the toughening process improves strength, not thermal properties.

Does temperature affect the thermal conductivity of glass?

The thermal conductivity of glass remains stable at normal temperatures. It only begins to increase at a temperature of 300°C (572°F) or more.

Does the thickness of glass affect its thermal conductivity?

Yes, the thickness of glass affects its thermal conductivity. Adding thickness to a pane of glass increases its insulating properties.

That said, the impact of thickness is less significant than other factors, such as air gaps in double- and triple-glazed units and low-E coatings.

Why does thermal conductivity matter?

Energy efficiency affects the decisions made by architects, designers and other stakeholders involved in the construction of public and residential buildings. The thermal conductivity of glass is a crucial factor when it comes to ensuring the thermal efficiency of our buildings. 

Compared to metals, glass is naturally a poor conductor of heat and can lead to heat loss in buildings. This means thermally efficient products are required to help manage energy consumption, optimise occupant comfort and ensure compliance with building regulations.

Key takeaways

• Glass has a low thermal conductivity – between 0.5 and 1.4 W/mK.
• Because of this, thermal efficiency in glass is an important consideration.
• When sourcing glass for a building project, look for thermally efficient glass
  
  

Are you looking for high-quality, thermally efficient glass products? As commercial glass specialists, we've supplied top construction and architectural firms since 1993. Get in touch with ToughGlaze today for a quick, competitive quote.