Building Sustainability
Energy efficient house design for hot arid climates
- Orient house to the north to minimise east and west wall area exposed to the morning and afternoon sun and maximise solar heating in winter. North-south dimension should be approximately half east-west dimension.
- Correctly sized pergolas and eaves shade windows and walls in summer but let the winter sun in.
- Windows are generally located on the north and south
walls only. Large windows on the north let more sun in
during winter days (large southern windows are a source
of winter heat loss).
- The illustrated eave angles let northern sun strike Alice Springs walls from 22 March – 22 September. However as summers are long and hot and winters are relatively short, it its more important that good shade is provided throughout the year than passive solar heating in achieved in winter.
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- For other hot arid regions the northern eave angle required to shade windows from August to April can be calculated using the following equation: northern eave angle = (latitude + 11) degrees
- During summer the sun is in the southern half of the sky. Avoid heat gain in summer by: maximising southern eave and verandah widths; limiting southern window areas; ensuring window sill heights are as high as possible to maximise shading by eaves; using wall materials with good insulation properties; and using vertical wing walls to shade windows and walls from the low west-southwest and east-southeast sun.
- Deciduous trees to the north shade in summer and let winter sun warm the house.
- Light coloured paint reflects a lot of the heat away from walls and roof.
- Roof space ventilation draws heat out in summer. However a sealed roof space is best in winter. Ventilation which can be closed off and sealed in winter is ideal.
- Buildings are sited and landscaping is designed to provide shade towards the east and west walls and roof all year around. Consider leaving half roof unshaded if solar panels to be used.
- Once the sun is in during winter, exposed internal heavy mass construction materials such as concrete and bricks absorb heat during the day and release it later to keep rooms warm.
- Choose roof and wall types with high insulating properties (R-values).
- Choose wall type with internal heavy mass and the highest R-value possible. Reverse (inside out) brick veneer with sisalation makes sense.
- R2.5 minimum recommended roof/ceiling insulation level (including foil/sisalation).
- Make the most of breezes in summer:
- Buildings are designed with openings on opposite or adjacent walls for cross ventilation.
- The predominant evening wind direction for Alice Springs and Tennant Creek is south-east throughout the year.
- Reduce other sources of heat
loss and gain.
- All windows should have curtains or blinds that stop air circulation against the windows surface. Heavy curtains which seal and are tipped by a pelmet are most effective.
- In summer, close curtains and blinds during the day to keep out the heat.
- Weather seal gaps around windows and doors.
- Choose low energy heating and cooling equipment
- Air flow from fans makes you feel 3-5 oC cooler for less than 80 watts.
- Evaporative coolers use much less electricity than refrigerated air conditioners. Ensure cooling outlets seal automatically when not in use.
- Natural gas, LPG and reverse cycle (refrigerative) air conditioners are highly efficient for heating.
- Whilst wood heating has a local impact on air quality, wood heating has very low greenhouse emissions if the wood is from a sustainable source (i.e. new growth replaces that taken away).
- Don't overheat or over cool: 1 oC difference in temperature between indoor and outdoors adds up to 10% to cooling and heating bills and greenhouse emissions.
- Switch off cooling and heating appliances when you go out.
| Note: In January 2003 Minimum Energy Performance Requirements were introduced into the Building Code of Australia. These requirements are a minimum, meeting them is not the same as adopting best practice energy efficient design. |