Feature

How to get the most out of windows

G Magazine

Windows are not just dressing to a house; they also make a big difference to how much heat and energy your home uses. So how do you make your windows work for you?

windows

Credit: iStockphoto

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We think of windows as providing some protection from the outside world as we gaze out - indeed they do, but not as much as you might think. Even though they protect us from rain and wind, they also let about one third of a home's heat escape.

"Windows are the weakest thermal element in a house," says Leigh Duxton, advisor for Canberra-based Home Energy Advisory Team.

So what can we do to prevent our home's warmth from rushing out the window?

Build efficiently

The most cost-effective way of creating an energy-efficient home is to consider these issues when you're in the design stage. As well as the location and size of windows, the orientation of the house and type of insulation and materials should all be factored into the home's design.

Ideally, you want most of your windows (if you're in the Southern Hemisphere) facing north, with one or no windows on the west and east, and only a few on the south. This arrangement will make the most of northerly sun for winter warming while limiting how much hot westerly sun penetrates in summer.

The size of the windows and where you plan to put them depends on a number of factors, not least the angle of the sun, which changes with the seasons and latitude. So it's a good idea to find an architect with an understanding of home energy rating tools to advise you when the time comes to renovate or build.

Choose efficient windows

With thousands of windows on the market and 27 different basic types of glazing to choose from, buying a window can be quite bewildering.

Basically, there are two issues to consider - the U value, which is how easily heat moves through a window, and the SHGC (solar heat gain coefficient), which measures how well a material blocks heat from sunlight. A low U value is recommended in all climates, but the ideal SHGC will vary depending on where you live.

If this all sounds a bit confusing, don't worry - the Window Energy Rating System (WERS) is a star rating system to simplify the decision process. The label is split in half, with blue stars to describe which windows work well in winter and red stars for summer.

WERS administrator, Michael Palin, suggests "Choose at least a 2.5-star rated window for a mixed climate", meaning a climate which is both hot and cold, such as Canberra. "For more extreme heating or cooling climates such as Hobart or Darwin, aim for at least 3.5 stars."

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