The Australian Dream Series

 
 
 

Energy Efficiency

Energy efficient design requirements are mandatory across all of Australia under provisions in the performance based 'Building Code of Australia'. which sets out the minimum level of performance that a building is required to achieve.
In Australia, building control is the responsibility of the eight States and Territories. As such, each State and Territory has its own 'Building Act and Regulations' with the Building Code of Australia being referenced by all regulations as the construction standard for buildings, or building work

Under the BCA provisions, Australia is divided into 8 climate zones (see pdf map) with varying requirements for each zone in regards to the following aspects of house construction:
1. insulation for roofs, walls and floor,
2. restrictions on area of glazing in windows and skylights,
3. attached Class 10a buildings (garages etc) so as not to compromise the thermal performance of the main building,
4. air movement control and building sealing for better thermal performance, and
5. insulation of central heating pipe work and heating and cooling ductwork.
It should be noted that the BCA provisions are minimum performance requirements and any provision of the BCA may be overridden by, or subject to, State or Territory legislation.

For example requirements for total wall insulation values of R1.4 in zones 1,2,3 and 5 are amended in a Queensland variation to R1.0 in its zones 1,2 and 3.
In Victoria as of July 2005 all new homes must attain a '5 Star' energy rating level and include either a solar hot water system or a rainwater tank.

Despite the view by some that the various Federal, State and Territorial legislations have not been thought through properly the fact remains that a home designed for energy efficiency can be a more comfortable home to live in.
The ingredients that are combined to achieve an energy efficient home include correct site orientation, correct window size and placement, appropriate insulation levels, good cross ventilation capabilities, correct landscaping, the choice of energy efficient appliances, and a conscious effort by members of the household to close windows and doors to heated areas, to close curtains when heating rooms and maintaining correct thermostat settings on refrigerators and heating and cooling apppliances.

Site Orientation
Correct orientation of the home can be a complex item for many owners. Quite often suburban block limitations, the direction of views, privacy requirements and even overshadowing from neighbouring houses, can mean that a compromise or some very careful designing may need to occur to maximise upon the benefit of winter sun penetration and also cooling summer breezes.

For houses in cool temperate areas where we are looking to maximise upon winter sun penetration we would err in our orientation towards the west.
In sub tropical areas where we are primarily looking at keeping out the worst of the summer sun we would tend to go more to the east.

Cool Temperate - 5 degrees west of true north. Tolerance between 20 west and 10 east
Hot Arid - 25 degrees east of true north. Tolerance between 30 east and 5 west
Dry warm Temperate - 10 degrees east of true north. Tolerance between 15 east and 15 west
Hot Humid - 5 degrees east of true north. Tolerance between 30 east and 10 west

These are broad guidelines covering the predominant variations throughout Australia.

Correct window size and placement
The orientation and size of the windows effects the amount of heat entering and leaving a home.
In the cooler zones the general rule is to orient the house so the main wall and window areas face north, also minimise windows to the west and, to a lesser extent, to the east.
By placing living areas and main windows to the north it allows rooms to be heated during the day by low winter sun, thereby reducing the need for artificial heating at night.
In hot zones there is more emphasis on excluding sun penetration and orientating to maximise on the predominant cooling breeze direction.

The full extent of good energy efficient design is not covered here due to the many variables that can be in place depending on your geographical location and specific site considerations that would need to be taken into account.
Most Building Designers have a good knowledge of both 'passive' and 'active' solar design and will employ 'Thermal Performance Software' during the design process as an aide, but it is an area that you need to study in depth to be familiar with so that you can be 'on the same page' when in discussions with your designer.

 

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