Windows
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Windows can be one of the biggest sources of heat loss and gain in your home. Almost 90% of a home’s heat is gained, and up to 40% of heating energy is lost through its windows.
Improving the efficiency of your windows can lead to big savings on your energy bills.
Natural light
Make the most of natural light in the daytime during the cooler months when allowing the sun to heat your home is desirable. This will make your home more comfortable and help reduce reliance on artificial lighting.
Avoid placing furniture in front of windows to make the most of your natural light.
Seal gaps
Gaps around doors and windows create draughts that diminish the energy efficiency of your home. Draughts mean your heating and cooling systems need to work harder and longer to maintain comfortable temperatures.
Signs of gaps to look out for include rattling or whistling sounds during windy weather, moving curtains or feeling a breeze near closed windows. You can also identify gaps by hiring a qualified technician to perform an air-leakage analysis on your home.
To seal gaps around windows, you can:
- fit foam strips around the window frames
- use sealant, expanding foam, or a gap filler rod around architraves or window frames (always check the manufacturer’s label for instructions).
An open window allows heated or cooled air to escape and undesired hot or cold outside air to enter the home. Always heat or cool a room with the windows closed, unless using an evaporative air cooler.
To find out more about draught proofing visit Your Home’s Ventilation and airtightness chapter.
Window coverings
Maximise temperature control all year-round by installing close-fitting lined curtains or blinds and pelmets. When choosing curtains or blinds for your home, make sure they:
- reach the floor and wrap to the wall on either side of your window
- are lined with a light-coloured ‘block out’ backing to prevent heat loss in winter and heat gain in summer
- are made of tightly woven material to trap moving air
Change how you use your window coverings between the cooler and warmer seasons:
In cooler months, open the coverings during the day when the sun is shining to warm up your home. When the sun is no longer shining in, close the coverings to retain heat inside the house.
In warmer months, close the coverings during the day to keep your home cool. When the sun sets, open coverings to let the evening breeze blow through your home.
External shadings
Shading your home, particularly windows, glass doors and skylights, can have a significant impact on comfort and energy bills.
The best approach to shading your home depends on your climate and orientation. These tips outline general principles, but it is best to get personalised advice from an energy assessor, building designer or other relevant professional.
Maximise shading in tropical climates and minimise shading in cold climates. In temperate climates, let the sunshine in during winter and provide shade in summer.
Shading should work with orientation to make your home comfortable and reduce your energy consumption. For most of Australia (excluding northern Australia), glazing facing the north is the simplest to shade. However, appropriate shading solutions are available for any orientation.
Use seasonal outdoor plants, a pergola or other shading devices to keep direct sunlight off your home as needed. This is particularly important for minimising heat gain through your windows in warmer months.
Find out more about shading on Your Home.
Glazing
Glazing refers to the glass installed in the window frame. Most Australian homes were built with single panes of glass known as single-glazed windows. Double and triple-glazed windows are becoming more popular for energy efficiency reasons.
Single-glazed windows
Single-glazed windows consist of one pane of glass, typically between 3 and 10 mm thick. They offer minimal insulation making them inefficient at regulating temperatures. This allows heat to easily escape in winter and enter in summer.
Single-glazed windows are also prone to draughts due to gaps and poor sealing around window frames, which contributes to energy loss.
Double-glazed windows
Double-glazed windows consist of 2 panes of glass separated by a sealed gap. The gap between the glass can be filled with air or with an insulating gas such as argon or krypton. This space acts as a thermal barrier, significantly reducing heat transfer between the inside and outside of your home.
Double-glazed windows can reduce heat loss by up to 30%.
To better understand your potential energy savings, you can explore the Window Energy Rating Scheme (WERS), which rates windows for both heating and cooling performance.
Triple-glazed windows
Triple-glazed windows consist of 3 panes of glass, separated by spacers that create 2 insulating gaps.
Triple glazing allows good solar heat gain and is typically better at preventing heat loss.
In Australia, double-glazed windows are usually sufficient for energy efficiency and comfort. Triple glazing is recommended for extremely cold climates, though it can diminish desirable solar heat gain in winter from north-facing windows, compared to double glazed windows.
Find out more about window glazing on Your Home.
Frames
Next to glazing, window frames play the most significant role in your windows’ thermal performance. Frames can be made from a variety of materials, including:
- timber
- un-plasticised polyvinyl chloride (uPVC)
- aluminium and thermally broken aluminium frames
- a combination of these materials
Energy-efficient window frames are made from materials that don't transfer heat and cold. For example, timber frames do not conduct heat and are highly energy efficient. However, they require a lot of maintenance compared to aluminium and uPVC frames.
uPVC frames perform similarly to timber but are more durable and require less maintenance.
Aluminium frames are a popular choice. They are light, durable and require little maintenance. However, aluminium is a good heat conductor resulting in unwanted heat loss and gain.
If aluminium is selected for the frame, ensure the window is thermally broken. Thermally broken aluminium frames reduce heat transfer between the interior and exterior by incorporating a non-conductive insulating barrier between the inner and outer profiles.
Combination frames – typically aluminium with timber – leverage the low maintenance benefits of aluminium as the external component and insulating properties of timber as the internal component.
Read more
Insulation and draught proofing
Passive design Your Home
Window glazing or treatments ACT Government
