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Windows, doors and skylights

Poorly designed windows, doors and skylights can make your home too hot or too cold. If designed correctly, they'll help maintain year-round comfort, reducing or even eliminating the need for mechanical heating and cooling depending on your local climate conditions.

Heat transfer through the door or window itself, and draughts caused by gaps and cracks around doors, windows and skylights can both contribute to a high level of energy loss, severely reducing the effectiveness of heating and cooling. The impact on your comfort and costs can be considerable, for example:

  • Up to 40% of your home's heating energy in winter can leak out through windows or skylights.
  • Up to 87% of your home's heat gain in summer can be through windows and skylights.
  • Draughts around doors, windows and skylights can add up to 25% to your heating and cooling bills.

There are plenty of options to help you ensure your windows, doors and skylights are doing their job but not adding to your energy bills—and in the case of sealing gaps and cracks, the remedies can be quite simple and low cost.

Windows

Windows provide light and fresh air, but can also allow warm air to escape from inside during winter, and let in too much heat during summer. There are a number of options to help you save on heating and cooling whether you're building or renovating, or looking to improve the efficiency of existing windows.

  • If building or renovating, you'll need to carefully consider the right type of glass and frames, size, location and shading of windows with your architect or builder to suit the climate and orientation of your home.
  • Do your research as there are many different types of windows and frames to choose from and each product will have a different effect on light, noise control, security and energy efficiency. Matching the right type of window and glazing for your situation and needs in each season will save you money over time.
  • The Window Energy Rating Scheme (WERS) rates the energy-related performance of windows, skylights and glazed doors—the more stars the better. The Australian Window Association website has window climate zone guides for more information on what kind of window is most energy efficient for your climate. You can also search and compare the WERS energy efficiency ratings of products available in your state or territory.
  • Most windows in Australia have a single pane of glass, but double glazing—or even triple glazing—can have significant energy saving benefits for reducing winter heat loss and summer heat gain. This is because they trap air between the panes acting as insulation and helping to make the temperature of the inside of the window as close as possible to the desired room temperature.
  • Double glazing is particularly recommended for rooms where internal coverings such as curtains are not desired or practical such as the kitchen.
  • It's important to note that unprotected double-glazed windows will still require summer shading as additional glazing does not stop the sun coming in.
  • In an existing home, the decision of whether to retrofit double or triple glazing will depend on your heating and cooling needs against the costs.
  • To provide protection from summer heat gain, external shading devices such as awnings, roller blinds and one metre deep eaves on north-facing walls, provide the most effective results followed by well-chosen tree plantings. Depending on your situation, window films can be a cost effective way of reducing solar heat gain, and can be applied to existing glass windows at low cost.
  • Installing window furnishings, such as awnings, pelmets, blinds and curtains, can increase the efficiency of your windows year round. It's important to talk to your local supplier to find out what furnishings are best for your home and environment.
  • Keep in mind that the material of the window fame can affect the overall window performance. Timber and PVC generally perform better than metal frames such as aluminium. In an existing home, window frames that aren't properly fitted can let out more heat than the window itself due to cracks and gaps around the frame.

Doors

Doors aren't something that immediately come to mind when thinking about the energy efficiency of your home. However, the types of doors and treatment you have, their age, as well as door use and maintenance are all factors that can influence the comfort of your home as well as your costs.

  • Draughts from around doors can account for 25% of your heating and cooling bills. Exterior doors in particular can contribute significantly to air leaks, and can also waste energy through conducting, especially if they're old, uninsulated, or improperly installed and sealed. Draught-proofing can reduce the energy losses due to air leaks.
  • Glass or patio doors, especially sliding glass doors, can be much less energy efficient than other kinds of doors as glass is a poor insulator. If you're thinking of buying new glass doors, ensure they have appropriate insulation and glazing. An energy-efficient door may cost more upfront, but you'll save money on your heating and cooling costs in the long run. If you have existing glass doors, consider investing in some window furnishings to prevent heat loss in winter and heat gain in summer.
  • Make sure your doors are properly insulated. This is especially important for external doors, and doors between rooms where you have heating or cooling on as well as rooms that don't require temperature control, such as the bathroom. If your garage is attached to your home, make sure the door between the garage and the house is adequately insulated, it might also be worth insulating your garage door.

Skylights

Skylights can let in more than 3 times as much light as a vertical window of the same size. Using natural light will help brighten up your home and means that you don't have to rely as much on artificial lighting. Reducing the size and number of windows overall can help reduce heat loss and gain minimizing the need for additional heating and cooling—which can add up to savings on your energy bills.

  • Skylights are an efficient way to admit daylight to your home and distribute it evenly, adding significantly to your energy efficiency and comfort.
  • They can be fitted in new or existing homes and are particularly useful for spaces where space restrictions or location do not allow regular windows such as hallways, attics or internal laundries or bathrooms.
  • There are many kinds of skylight available, from roof windows to tubular skylights—sometimes called tubular daylighting devices (TDDs). TDDs capture direct sunlights and diffuse it at ceiling level around the room and work well in climates with lots of clear, sunny days.
  • Skylights can use the same energy-efficient technologies used in other window designs—including glazing that blocks or admits sunlight depending on its angle allowing overhead summer sun to be avoided. Additional features such as shafts, tubes and ceiling diffusers, as well as blinds and shades, can be used alone or in combination to reduce solar heat gain and introduce light to where it's needed.
  • Choose the best option for your location, depending on your climactic zone and the orientation of your home. Your local supplier should be able to tell you which type best suits your room and climate. Skylights come in standard sizes or can be specially made for your home.
  • Fitting the right size of skylight will allow you to let the required amount of light into your home. As daylight provides cool light, there is less heat gain than most types of artificial light.
  • If you have an older skylight, think about upgrading it to benefit from design improvements including glazing and insulation. Sealing gaps and cracks or installing covers or blinds are also options to improving energy efficiency and functionality.
  • Maintaining your skylights by lubricating moving parts, cleaning exteriors and removing debris will help ensure they perform at their best.
  • While upfront costs can be high, improvements to the comfort, lighting, look and feel of your home as well as the potential for energy savings, are giving skylights even greater appeal.

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Heating and cooling uses 40% of the energy in the average Australian home.

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