An energy efficient home is designed to deliver maximum comfort to occupants by:
- making the most of free natural heating, cooling and lighting
- utilising efficient design principles and building materials to reduce the need for appliances.
An energy efficient home costs no more to build than a conventional home and:
- is more comfortable and easier to maintain
- has reduced energy bills and greenhouse gas emissions.
A great way to find out more about designing an energy efficient home is to visit one of the open houses on Sustainable House Day in September each year. Visit sustainablehouseday.com for more information.
For a home to be energy efficient it needs to have all the right elements of design. These include consideration of the following things that are provided on this page:
Orientation and location of the home
Layout and zoning
Insulating your home
Glazing - windows, skylights and other glazed surfaces
Shading
Landscaping
Ventilation and draught proofing
Thermal mass
Orientation and location of the home
The home should be orientated and located on a block to maximise the amount of sunlight it receives.
When selecting a block of land consider:
- the size, orientation and slope of the block to maximise sunlight entry
- tree coverage and height to avoid too much shading
- height and proximity of surrounding buildings to avoid overshadowing.
The ideal location is with the daytime living areas facing north and the long axis of the house running east to west.
Summer sun: The sun is
higher as it moves across
the sky in summer
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Winter sun: On winter days
the sun is low in the sky as
it moves from east to west
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Variations on house orientation can occur if the house can't be located facing north, up to 30 degrees east or 20 degrees west of true north. In these cases extra shading may need to be considered for summer.
Large windows on the north side of the house let the sunshine in during winter because of the low angle of the sun. Eaves prevent sunshine entering the house in summer because of the high angle of the sun.
To prevent overshading from neighbours to the north, allow a set back of:
• six metres from a single storey home
• 11 metres from a double storey home.
If this distance is not possible you may be able to use a clearstorey to allow adequate sunlight into the house. A clearstorey is a series of windows on a wall between a lower and a higher roof level. These windows will need sufficient shading in summer.
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Layout and zoning
Daytime living areas should be located on the north side with large north facing windows to capture the winter sun. Bedrooms and utility areas should be located on the south side. If the design allows it, bedrooms and other rooms can also face north.
Following a plan with open style living areas will help to:
- make best use of the available space
- allow sunlight to easily enter the home
- allow air to circulate freely around the home.
Design open plan areas so they can be zoned by closing doors. Zoning reduces the area you need to heat and cool, see Improving the effectiveness of your heating and cooling appliances.
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Insulating your home
Insulating your home is the most important measure for making your home energy efficient, see Insulating your home.
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Glazing - windows, skylights and other glazed surfaces
Windows and other glazed surfaces in an average insulated home can account for more heat gain or loss than any other aspect of the building fabric.
Choosing the right size windows and the right glazing material can significantly improve the efficiency of your home.
Window size and location
Ideally all north facing windows should be full length to allow the heat from the winter sun in. East and west facing sides should have a minimum area of glass or none at all.
Sunlight shining directly on north, east and west facing windows produces the same amount of heat per square metre as a one bar radiator.
As a general guide, the total window area should be less than 25% of the total floor area of the house. A guide to the percentage of window area to wall area for each direction is:
- north facing - 60%
- south facing - 30%
- east facing - 15%
- west facing - 0-7%.
House energy rating software considers a range of design features when assessing the overall energy efficiency rating of the home and can provide more accurate proportions.
Thermal performance of windows and glazed surfaces
The measurement of how well a window or other glazed surface can prevent heat from entering the house is its R-value. A higher R-value means less heat is transferred through the glass.
The inverse of the R-value is called the U-value which measures how well heat flows through the glass. A lower U-value means less heat will flow through the glass.
Another measurement that is given with windows is the solar heat gain coefficient. This number represents the percentage of heat that enters the home from direct sunlight. A lower number represents more direct sunlight being reflected away from the glass and less entering the home.
More detailed information on glazing is available from the Australian Government.
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Shading
Shading is vital for keeping your house cool in summer. Well designed shading can greatly reduce:
The most effective way to keep the summer heat out is to use external shading. Focus on north facing windows which receive the most direct sunlight and then east and west facing windows. South facing windows generally don't need shading.
External shading should be designed to let in the winter sun but totally shade the summer sun. External shading can include:
- overhanging eaves
- horizontal shades or awnings
- pergolas.
Internal shading is not as effective as external shading for preventing the sun's radiant heat from entering the home. Internal shading such as curtains and blinds should be opaque and light coloured to reflect the most sunlight.
Tinted or reflective glass should be used where views shouldn't be obstructed. If external shading can't be installed use internal shades with a reflective backing.
Curtains and blinds together with pelmets will help to keep heat inside the home. They prevent warm air from coming in contact with the cold glass.
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Diagram showing heat loss and cold draught without pelmet installed and heat retention with pelmet installed |
Landscaping
Landscaping can help to maintain comfortable temperatures around your home. Breezes entering your home will be cooler if they have passed through gardens or courtyards that have shade, ponds, shrubs and lawn. The layout of your garden can also be used to screen or direct breezes.
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Ventilation and draught proofing
Cross ventilation occurs when two sides of the home are opened to allow air to flow from one end to the other. Encouraging airflow on summer evenings is an effective means of cooling the house and occupants at night.
It is important to be able to control ventilation and prevent draughts. Draughts can create discomfort and lead to energy losses in both summer and winter.
In winter, draughts can account for 25% of heat loss. Reducing draughts is a cheap and cost effective way of reducing heating and cooling costs.
Draughts can be reduced by sealing:
- cracks and gaps between walls, ceilings, floors, windows and doors
- unnecessary vents
- exhaust fans and outlet grills
- unused fireplaces
- vented skylights
- ceiling evaporative ducts during colder months.
Gas heaters require adequate ventilation. Check with a licensed gas fitter before sealing any exhaust fans or outlet grills.
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Thermal mass
Thermal mass refers to the ability of building materials to store heat. Building materials with a high thermal mass can store large amounts of heat without a large temperature change. They include:
- internal bricks and masonry
- concrete slab with hard floor coverings.
In places where the difference between day and night temperatures is 8°C or more, correct use of thermal mass can help to keep internal temperatures at a moderate level by averaging day and night temperature extremes.
Concrete, tiled or slate floors can absorb heat during day in winter and then release the stored heat into the room at night. They work best in rooms with north facing windows. Carpets and rugs act as insulations preventing the floor from absorbing heat.
A balance needs to be achieved between thermal mass, window areas and insulation levels to suit climatic conditions.
Poor use of thermal mass can cause:
- absorbed heat to radiate at night during summer
- heat you produce on a winter night to be absorbed.
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More information
Other websites
Six star energy efficiency requirement for new homes - Department of Planning, Transport and Infrastructure
Your Home Technical Manual - information to encourage the design, construction or renovation of homes to be comfortable, healthy and more environmentally sustainable.
sustainablehouseday.com - An event held in September every year showcasing sustainable houses around Australia.