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51. Construction - Eco House - Energy Efficient

As per above (Carbon Reduction), even if a house is providing 100% of its own energy, there is still environmental benefit in being energy efficient. Any energy you can save will be fed back into the grid to alleviate some of the carbon-based energy demands from other households.

The design stage is responsible for 67% of ongoing household energy use on average. This is broken up into:

  • Heating and Cooling - 40%
  • Water Heating - 21%
  • Lighting - 6%

The remaining 33% is attributed to appliance use which is mostly the responsibility of the occupants.

To reduce load on heating and cooling, the passivhaus principle can be used, or alternatively, if the site is appropriate, a low-cost passive solar solution can be designed.

Passive Solar is a design concept that utilises the sun to increase and regulate day/night temperatures during winter and maintain cooling by shielding the sun and cross ventilating in summer.

As new home designers in the Northern Beaches we find the mandatory conditions for a successful passive solar design are:

  • Ability to orient living areas to the North.
  • High amount of glazing on the northern side
  • No major overshadowing from other buildings, evergreen trees or topography.
  • A design that is typically only one room deep from the outside walls.
  • Willingness to have exposed thermal mass materials. E.g. Bare interior brick/masonry walls, polished concrete slabs.

In the summer when the sun is at a higher angle in the sky it is prevented from entering the house and coming into contact with the thermal mass by awnings, eaves or other shade structures. Computer modelling is the easiest way to determine the depth of the required shade device according to the sites longitude, latitude and orientation. Because material with high thermal mass take a long time to heat up from a direct heat source, it keeps the house much cooler in the summer than a traditional house. The design should allow cross-ventilation and feature high windows to allow rising hot air to escape.

In winter, when the sun is lower, the design encourages solar radiation to penetrate through windows, past awnings, and come into contact with thermal mass. This thermal mass maintains energy much longer than the air does and it releases this solar heat slowly over the night helping to regulate day/night temperatures into a more stable 24-hour indoor climate.

The important construction detail to ensure the success of this strategy is to insulate the sides and underside of any slabs to make sure heat does not ‘leak’ downwards, and to insulate the outer side of any thermal mass walls. 

In regards to water heating, cost and energy can be kept to a minimum by specifying water saving taps to reduce hot water consumption and in specifying the most appropriate and efficient water heating unit. For more information on water heating options and their advantages and disadvantages see Chapter 5.2 Water Heating.

LED technology has come very far in the last decade. Once only available in cool, sterile colours, LED downlights are now comparable in colour to the outdated halogen. They are far more energy efficient, brighter, throw a wider beam and each globe should last at least 10 years.

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