The following notes on energy-efficient housing design were taken from an article published by the Queensland Master Builders Association.

"It is now widely accepted that greenhouse gas emissions are causing increases in environmental temperatures, which in turn produce climate change and all its potentially disastrous consequences. At the Kyoto Convention on Climate Change, Australia gave a commitment to reduce its rate of greenhouse gas emissions. To achieve the promised reduction in emissions, unilateral action from all tiers of government and all members of the community is required.

Greenhouse gas emissions from the household sector produces about one fifth of Australia's total. Most of this is from energy use in the home. On average, heating and cooling requires the most household energy, followed by electrical appliances, water heating and cooking.

The subtropical coastal regions of Queensland enjoy a mild climate. Residential buildings can be constructed so that almost no additional heating or cooling energy need to be used to maintain year-round thermal comfort for their occupants. This can be achieved without major lifestyle changes, just simple design features.

Principles of Energy Efficient House Design
The design of an energy efficient house is based on simple principles relating to orientation, building envelope, thermal mass, window size, shading and ventilation and insulation, and will be influenced by constraints on each individual site.

Orientation
The home should be sited, where possible, to capture the warm winter sun to heat the home and to avoid sun entry into the house in summer. Ideally, living areas should be located facing north to capture the winter sun. By doing this, control of the summer sun can be achieved more easily by the use of eaves for shading. Likewise, windows on the southern side have little direct sunlight. Therefore, bedrooms are best positioned on the southern side creating cooler sleeping areas. The laundry, bathroom, garage and storeroom are best positioned on the western wall of the building to minimise heat entry into the living area. Verandahs should be positioned to capture views and breezes with the eastern and western sides being ideal as they protect the home from east and west sun and provide an alternative recreation area for different times of the day.

Building Envelope and Thermal Mass
Materials used in the external envelope affect the performance and comfort of a building. Heavyweight materials (high thermal mass) absorb heat during the day and therefore result in lower daytime temperatures, if the windows are adequately shaded.

Ideally, living areas should be built from heavyweight or well-insulated lightweight materials and shaded from the sun, while bedroom areas should use lightweight construction as they cool down quickly.

Insulation
In a typical uninsulated house in summer, around 25-35% of heat gain occurs thought the ceiling, 15-20% through the walls, 15-25% through the floors, 25-35% through the windows and 5-15% through hot air draughts. Correctly installed insulation can provide great benefits. The level of performance of an insulation product is measured by its thermal Resistance or "R-value". The greater the R-value, the more effective is the insulation. Ideally insulation with an R-value of 2.0 or 2.5 should be installed in the ceiling.

Windows
Size and location of windows should be determined according to the orientation and type of materials used in the house. Windows on the north allow greater solar access during winter and should be shaded to prevent direct sunlight and heat gain during the summer months. East and west facing windows should be reasonably small with good summer shading. South facing windows do not receive direct sunlight and have a minimal effect on heat gain.

Shading
Well designed shading greatly reduces heat entry, especially on east and west sides of a building. Shading devices, which may include eaves, external blinds, shutters or a slatted pergola, should be designed to allow sun entry in winter and totally shade the windows in summer.

Ventilation
Air movement throughout the house is required to remove the heat build-up of the day. Siting of a house should therefore take into account the direction of prevailing winds to optimise the use of these winds for ventilation. House layout incorporating air passages ensures that he best possible flow through ventilation is achieved. Small low openings on the windward side and larger raised openings on the leeward side maximise the air speed in the room.

Energy Rating Schemes
Computer simulation programs have been developed to assign star rating from 0 to 5 stars to a house. Details of house design, construction and orientation are entered into the program. Designers can also enter design modifications to see what effect these have on the star rating.

Where To From Here?
As the Energy Efficient Code is now part of the Australian Building Code Designs must now incorporate theseElements into their Design & provide criteria that satisify the code.

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