Window glass can be treated to reduce the amount of solar energy transmitted through it. The type of glazing you choose can help you to:
Single-pane glass windows will leak heat in winter and gain heat in summer. Double glazing is a much more efficient style of window but there are also treatments you can apply to the glass and windows to reduce the amount of solar energy passing through them.
Double-glazed windows are very energy efficient, as they can reduce heat loss or heat gain by almost 30% in comparison to single-glazed aluminium windows. Double glazing can contribute significantly to a 6 star or higher energy efficient home and is widely available.
Triple glazing performs even better than double glazing to further reduce heating and cooling costs and is ideal for colder Victorian climates.
Remember, the type of window frame is just as important as the glazing.
In Victoria, adding a low-e coating to the internal pane of glass will help make your house warmer in winter by reflecting radiant heat back into the room. Low-e glass is generally only used as a complement to double-glazing to reduce winter heat loss through windows. The use of low-e glass to control heat gain is not recommended for Victorian conditions as it also reduces the amount of solar gain in winter.
Secondary glazing is an extra pane of glass or clear acrylic that is retrofitted to existing single-glazed windows through magnetic strips or built onto the existing frame, and is often a cheaper alternative to double or triple glazing.
Depending on the product and its ability to create an air space between the existing window and the second layer, it may be possible to mimic the properties of a double-glazed window. Secondary glazing treatments are a popular solution for improving the energy efficiency of heritage windows, as they maintain the existing character.
Magnetic and transparent films can be fitted either to the frame or the glass of an existing window. The glass can also be treated to reduce the amount of leaking solar energy. Common products include;
Toned glass – A tint is applied to the glass during manufacture to reduce the amount of heat transmitted through it. Tinted, or toned glass can also reduce light and heat gain in winter as well as Summer.
Reflective coatings – Can be applied to new and existing windows. These tend to stop greater amounts of heat gain than some toned glass.
Your window supplier or installer can provide valuable ideas and industry knowledge, but it is important that you ask the right questions.
The Window Energy Rating Scheme gives a star rating to a window's glazing and frame energy performance, making it easier to compare different windows and decide which is best for your needs.