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Glass & Glazing - Energy Efficiency

As homes are heavy users of energy, the Building Code of Australia (BCA) now stipulates energy efficiency regulations for all residential buildings so that new homes will need less artificial heating and cooling.

Stegbar bushfire bi-fold doors Each State in Australia applies the BCA in a slightly different manner and so a range of different rating tools have been used to determine the energy performance of residential buildings nationally.

In order to be able to be used with these software rating tools, windows must be rated under the Window Energy Rating Scheme (WERS) with the information verified by the Australian Fenestration Rating Council (AFRC). WERS rated residential windows have star ratings and percentage improvements to help give an easy comparison of windows, however it is specifically the U-value and the solar heat gain coefficient that are required and used in this rating tools.

Your designer or builder should use an authorised computer modelling package to explore different ways of using building materials including glass; as well as other passive energy efficiency techniques such as eaves, shading, location and orientation; while ensuring adequate ventilation and natural lighting, to meet energy efficiency requirements.

The focus on maintaining good design principles for your home, rather than the specific energy performance of any one building element, will provide you with a home that not only complies with energy regulations, but one that is comfortable for you to live in.

While there are 69 climate zones defined in the BCA, essentially all of them fall into three broad categories:

  • Cooling climate (the largest use of energy is in cooling the home): the energy efficient solution is to keep the sun’s rays out and the cool air in. In this climate zone (tropical, subtropical or hot arid) the best results are obtained from windows that limit solar heat gain on all orientations (low solar heat gain coefficient). Good insulation (a low U-value) is also beneficial, especially if the home is air‑conditioned.
  • Mixed climate (the use of energy is equal between cooling and heating the home): requires a home that can minimise the effects of the sun’s heat during summer, then insulate and utilise solar heat gain in winter. This means different glazing solutions. In this climate zone (temperate) the best results are obtained from windows that insulate well (low U-value), admit plenty of solar energy (high solar heat gain coefficient) on the north during cooler months, but limit solar heat gain from the east and west (low solar heat gain coefficient). Ideally, northerly windows should be protected by correctly sized eaves to prevent summer time heat and glare while still allowing sun penetration in winter.
  • Heating climate (the largest use of energy is in heating the home): the priority is to retain heat in the home and maximise the use of solar energy in winter. In this climate zone (alpine and cool temperate) the best results are obtained from windows that insulate well (low U-value) and admit plenty of free solar energy (high solar heat gain coefficient). Large west-facing windows may contribute to short-term overheating in summer, but glazing with a low solar heat gain coefficient must be used with caution on the west because of the energy penalty it can cause over the rest of the year.

View Stegbar WERS ratings.