What is SHGC?

What is Solar Heat Gain Coefficient (SHGC)?

With windows making up such a large part of a new build or renovation project it is important to know what you are getting from your supplier. Variations in window types, frame materials and glass can make a big difference to the overall performance of your home when it comes to energy efficiency and overall comfort.

When it comes to your windows, the conversation inevitably will come to glass, and one key measure on glass for the comfort of your home will be the Solar Heat Gain Coefficient or SHGC for short. But what is SHGC? How do you know what to look for?

Firstly, it is important to know a little bit about solar gain. Solar gain is the term given to the amount of thermal energy gained or lost by an object or structure when it absorbs heat from the sun. Basically, when the sun’s light hits an object how much heat is reflected by the object and how much gets absorbed and transmitted by the object. With this in mind, we can boil that down to a number that sits somewhere between 0 and 1. With 0 meaning no transmission of solar heat and 1 meaning all the solar heat is transmitted. This number is called the SHGC.

But what does this number mean for you when considering your glass options?

Simply put how much heat do you want to gain from the sun and how much heat do you want to block? In a cool climate a higher SHGC will allow more solar heat to pass through the window and help to heat the home, whereas in a warmer climate a lower SHGC will allow less solar heat to pass helping to keep the home cooler. Glass tints and low-e coatings  offer are some of the options to consider to get the best result for your project.

But what does this mean for you when planning your home? What considerations do you need to make? You will need to consider:

• The climate of your build or renovation location.
• What are the building materials that interact with the windows? E.g., insulation, cladding or other building materials.
• The design of the building. E.g., orientation, layout window position and size, roofing or shading.
• Glass type, Integrated glass units and the types of glass and coatings also play critical role in manipulating SHGC.

The overall performance that you get from your glazing will be a combination of all these factors the SHGC will form a part of that combination.

For more information to advise the glazing choices you have in relation to your project the best source of information is the Australian Glass and Window Association. On this website you can find the Window Energy Rating Scheme (WERS) that combines all the scientific information associated with window frames and glass and gives you the ratings you need to advise the best choices for your project. You can find the WERS details here.