The layout of the house in relation to the sun, and the use of features and materials that don’t maximise the use of solar energy, are important in keeping your house at the right temperature while saving on energy costs.
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Passive design is the control of ventilation and temperature without using any products that consume energy or money (such as heaters, dehumidifiers or fires).
Good passive design includes:
On average there are about 2000 hours of sunshine a year in New Zealand, although this varies by location.
Solar energy is most commonly harnessed for heating water using solar panels mounted on the roof. Electricity can also be generated directly using photovoltaic cells mounted wherever they can best capture solar energy.
Many of the local councils also have information about using solar power.
Fiona and her partner recently built a rammed earth house in Alexandra. The walls are 450mm thick and have proved to have very good energy performance in Central Otago's winter temperatures, which drop to minus 8 degrees.
They chose double glazed joinery, with wooden trims on the inside to reduce heat loss through the aluminium. They also put a double layer of wool insulation in the roof cavity, and selected a log burner with eco-flue to reduce heat loss in the flue itself.
The house maintains its warmth well beyond their expectations. It is positioned to trap as much heat from the sun as possible, which helps heat the house during the day and means that on sunny days (even when the temperature only gets a few degrees above zero) they have no need for the fire.
Note: The basic principle of rammed earth construction is the ramming of moist earth into a movable formwork to form thick walls that can store heat energy. There are building firms who specialise in this type of construction, and you can find information about earth buildings on the Earth Building Association of New Zealand’s website: www.earthbuilding.org.nz.
Combining passive and mechanical systems
A house that won a New Zealand Institute of Architects Supreme Award in 2004 incorporates the following features and materials:
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