There are many types of window assemblies with a large variety of glazing types that can go into that assembly. While most designers opt for aesthetics, we at Energy Rating Perth, aim for the energy efficiency of the selected glazing as well as the cost implications. We urge our clients to be cautious when selecting the type of glazing as well as window assembly as it will determine the thermal performance of their home for years to come. Energy Rating Perth’s energy assessors go beyond simply giving you an energy rating for your home, we can also offer advice on how to improve your energy rating by selecting the appropriate glazing for your home.

Windows are holes in the building envelope that allow the most heat exchange therefore they must be chosen with care for the optimum energy rating and thermal performance. The thermal performance of glazing is mainly determined by three variables;

  1. U-Value: This is the rate of solar heat transmittance through the glazing. It is denoted by a number between 0 an1. The lower the U-Value, the better the glazing performs in stopping the heat transfer.
  2. Solar Heat Gain Co-efficient (SHGC): This is the amount of solar heat transmittance. It is expressed as a number between 0 and 1. The higher the SHGC value, the more solar heat is transmitted than a lower value.
  3. Visible Light transmittance (VLT): This measures the percentage of visible light that will pass through a window. VLT is denoted by a number between 0 and 1. The higher the number for VLT, the greater the light transmittance.

While these values may seem simple to understand, they can have complex implications on the thermal performance of the glazing and are chosen according to the local climate as well as the target for the required interior temperature of your home. For instance, in summers, you might prefer windows with lower U-value and the same window should have a reasonable SHGC to allow ample solar heat gain in the winters. However, if it is a north window, you would prefer both the U-Value as well as SHGC to be high as you would want to maximise the solar gains from the north.

At Energy Rating Perth, our energy assessors use the latest software to model your home and suggest the best values for glazing performance. We work closely with your requirements to ensure the glazing in your home is optimum for appropriate passive solar design as well as cost efficient.


Contact us today for more information!