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A major principle of energy efficient building design is to allow the sun's heat into the home in winter while excluding it during the long hot days of summer. This can be achieved because the angle of the sun changes from season to season. In summer the sun rises earlier, south of due east and climbs high in the sky before setting south of due west. Major summer heat gain occurs through the roof and through the east and west windows and walls of the home. In winter the sun rises later, north of due east and stays low in the northern sky before setting north of due west. North facing windows and walls receive maximum winter sun and warmth.
The
Sun's Movement during summer (Dec)
The Sun's Movement during winter (Jun) 
If you are building a home and haven't yet purchased a block of land, the best block to choose is one which allows you to design your home with the living areas facing north, with no obstructions such as buildings or trees on this side of your home. Objects cast a shadow southwards approximately twice their height in mid-winter, so if you don't allow clear access between tall objects and the north side of your home you'll lose the sun's winter warmth.  If you've already chosen your block, there are a number of ways of varying your home design to make the best use of its orientation.  To achieve the design goal of optimal energy efficiency, an effective rule of thumb for a home in the southwest is to have north and south facing walls 1.5 to 2.0 times the length of east and west facing walls. This allows reasonable access to the winter sun from the north of the home, while reducing the exposure of walls and windows to early morning and late afternoon sun on the east and west sides of the home. True north is the ideal orientation for windows. However, if your eaves are designed correctly, windows oriented between approximately 20° east or west of north still allow good sun entry in winter while excluding most of the direct summer sun. Compass Card The Sustainable Energy Development Office has a handy compass card to help you orientate your home to take advantage of the seasonal sun movement. To obtain your copy of this simple to use tool simply email the Energy Smart Line with your name and postal address. Publications For further details, see the Energy Efficient Housing brochure (PDF 1MB). To access Adobe Acrobat Reader for the PDFs provided on this site: www.adobe.com.au |
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