Home window glazing

Last updated: 6 September 2022

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 window. Or single-pane window with curtain and pelmet in winter, and external shade in summer.

Glazing for new windows

Double- or triple-glazing

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.

From the most energy-efficient windows to the least efficient: triple glazing; double glazing, heavy curtains and pelmets; double glazing with low-e coating; heavy, lined drapes and pelmet; double glazing; unlined drapes/blind, pelmet; heavy lined drapes, no pelmet; vertical or venetian blinds; single glazing unprotected.

Tips for selecting double-glazing

  • The gap between the two pieces of glass should ideally be at least 12mm and filled with Argon gas for maximum performance.
  • If you are using double-glazing to reduce noise, a gap of 50–100mm should be used. Note that this will slightly reduce the thermal performance of the window.

Remember, the type of window frame is just as important as the glazing.

Low emittance glass (Low-e glass)

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 for existing windows

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.

Glazing films for existing windows

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.

Questions to ask your window supplier

Your window supplier or installer can provide valuable ideas and industry knowledge, but it is important that you ask the right questions.

Window Energy Rating Scheme

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.

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