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Understanding Energy Ratings - About Energy Efficiency

Hot Climate Zones 1, 2 & 3
Choosing energy efficient windows will make your home more comfortable, dramatically reduce your energy costs and help to create a brighter, cleaner and healthier environment. Windows are possibly the most complex and interesting elements in the fabric of our homes. They provide light and fresh air and offer views that connect our interior living spaces with the great outdoors.

However, windows can represent a major source of unwanted heat gain in summer and significant heat loss in winter. Windows can severely impact the heating and cooling loads of a building. Between 46%-61% of a home’s heating energy can be lost and between 79%-86% of its heat gained through windows. Improving their thermal performance increases comfort and reduces energy costs and Australia’s greenhouse gas emissions.

Find your climate zone at http://www.abcb.gov.au/en/major-initiatives/energy-efficiency/climate-zone-maps.aspx

Understanding Energy Ratings - Hot Climate Zones 1, 2 & 3

Considerations Keep solar radiation out of the home Retain coolness of air-conditioned air
Preferred U-Value Low
Preferred SHGCw Low
Other Factors Windows with high operable areas to maximise opportunity for air movement for natural cooling
Star Impact SHGCw optimised (tinted) - has the potential to improve up to approximately 1 star. U-Value - has the potential to improve up to approximately 0.25 stars for each unit reduction in U-Value. Ventilation - has the potential to improve up to approximately 0.25 stars per additional 20% of openable area.
Heating/Cooling Impact Each star corresponds to reduction in Heating/Cooling requirements of 15% to 30% on pre improved level. Star uplift due to reducing SHGC reduces cooling load but may marginally increase heating load in cooler months.
Cost and Green House Gases (GHG) Savings Approximately 3,000MJ of energy saved per star, mostly cooling - worth about $150-$250 and up to 0.35t of GHG. (Based on Brisbane, 240m house)
Notes:
  • This information is a guide only.
  • For more specific information refer to your window or glass supplier or the WERS Website (www.wers.net)
  • For window selection, Australian Building Code requirements and energy raters will specify actual U-Values and SHGCw for BCA-DTS or simulation tools such as AccuRate, FirstRate 5 or BERS Pro.

Understanding Energy Ratings - What The Stars Mean

U-Value (Uw) | Solar Heat Gain Coefficient (SHGCw) | Visible Light Transmittance (Tvw)
Everything in the 'building envelope' contributes to the overall energy rating. The most important factor is adequate insulation - but windows and doors are also important.

The star system used for window and door performance is to show relative performance, the same way fridged do. A 6 star house need to achieve a specific rating based on its location, and that rating is for the performance of the whole building - with each separate part doing its job.

For more information see our Solar Comfort Brochure

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