Energy Efficient Design

A buildings’ energy efficiency starts with the design. If energy efficient measures are not built into the design from the start, it becomes more difficult and costly to get it to the required 6 Star rating. There is a limit to the practical amount of insulation that can be installed into walls, floors and ceilings/roofs. Beyond certain points you start to get significant diminishing returns from the insulation, ie. Doubling the insulation will not give you double the benefit and effect on the building. The result is a greater requirement for increases in the glazing performance to more energy efficient glazing such as double glazing.

Therefore it is important to design your project with this in mind. Below are some considerations based on my experience and energy efficient design principles.

a) Property size: The greater the floor area and volume of conditioned air, the less efficient the property will be, and the harder it will be to achieve compliance.

b) Zoning: Grouping similarly conditioned rooms together (eg. Utility rooms, Bedrooms), will help reduce inefficiencies in heating and cooling.

c) Orientation: Daytime living areas should be facing north where possible. North windows to utility rooms or bedrooms will not have anywhere near the same positive rating impact compared to having these north windows servicing living areas. So where possible design living areas to the north, bedrooms to the south, and utility rooms to the east or west.

d) Glazing: Best results occur when the glazing to floor area ratio is less than 25%. Where this ratio exceeds 45%, the property may not be able to achieve compliance at all. Where possible, reduce east and west glazing areas.

e) Insulating properties of glass vs wall fabric: Full glazed walls, regardless of orientation, do not perform well. No glass can insulate as well as an insulated wall. Do not underestimate the value of wall area, as it is relatively cheap and much more effective to insulate walls, compared to even the most efficient glazed systems.

f) Shading: External retractable shading devices and garden plants/trees can be used effectively to maximise solar access in winter and minimise it in summer. Use of eaves in design as well as protecting the West side of the building is also valuable.

g) Lighting: The use of efficient lighting is highly recommended. Vented downlights should be avoided where possible.

h) Air Movement / Ventilation: Position windows and doors directly across from each other to allow as much unrestricted airflow through the building. Other ways of improving air movement and quality through the building could be the strategic use of ceiling fans and/or highlight louvre windows.

i) Sustainability: Where possible try to recycle and re-use.

  • Use water tanks to capture rain water for gardening requirements or even for toilet flushing.
  • Where appropriate try to source reclaimed materials, local materials and materials from sustainable sources.
  • Consider renewable energy sources such as solar for power supply and/or hot water supply.
  • Design your garden to get the most from the sun when you need it in winter and protect the building in summer.