Alice Springs experiences both extremes of climate – from subzero temperatures in winter, to over 40 degrees in summer. Whilst the use of some heating and cooling devices is inevitable, there are many steps that householders can take to maintain a comfortable home. These will help reduce the need for use air conditioners and heaters and keep energy bills down – in many cases you can save hundreds of dollars each year.
The building envelope (which includes the roof, walls, windows and floors of a home) has a significant impact on the amount of heat gain in summer and heat loss in winter. Ensuring that the building envelope is appropriate for the harsh Alice Springs climate is one of the most important factors in maintaining a comfortable, energy efficient home.
Your roof receives more direct sunlight than your walls and windows. A dark coloured or unpainted metal roof absorbs a large amount of this heat, which can easily pass through to your living areas. To reduce this heat flow, paint your roof a light or preferably white colour. Evidence from local trials has shown that you can reduce the temperature in your living areas by 3 to 4 degrees. Installing a roof ventilator (i.e. whirlybird) helps exhaust hot, stale air from your roof cavity, reducing the heat transfer to your living areas. Arid Lands Environment Centre and Alice Solar City are currently conducting trials in Alice Springs on the effect of painting the roof white. Stay tuned for the results.
A large amount of heat can be gained or lost through windows and walls. It’s therefore important to ensure adequate ‘protection’ of walls and windows in summer. This can be achieved by implementing one or more of the following:
In winter, warmth can be retained by:
Installing insulation in your home is one of the most cost effective measures you can take to help you stay warm and winter and cool in summer. It’ll mean that you stay comfortable naturally for a lot longer and can greatly reduce the amount of time that you do need to use an air conditioning and/or heating system (saving you money on your electricity bills).
Insulation works by creating a barrier to heat transfer through ceiling, walls and in some cases, floors. In summer it helps keep your home cooler by reducing the amount of heat entering your home. In winter it helps keep your home warmer by trapping the warm air inside.
For best results, all ceilings, walls and raised walls should be insulated, and the best time to do this is during construction. Insulation can be added to existing buildings with varying effectiveness and cost depending on the construction type and where the insulation is being placed. Retrofitting insulation is generally very common in Alice Springs as many houses were not insulated at the time of construction (though it is often difficult to retrofit insulation in walls).
There are two main types of ceiling insulation - bulk and reflective foil. The right type for your home will depend on the type of ceiling cavity, access available to the ceiling and personal choice.
Bulk insulation mainly resists the transfer of conducted and convected heat, relying on pockets of trapped air within the insulation. Its thermal resistance is essentially the same regardless of the direction of heat flow through it.
Bulk insulation includes materials such as fibreglass, rockwool, wool, cellulose fibre (shredded newspaper treated with flame retardant), polyester and polystyrene. For houses that have minimal ceiling cavity, including cathedral ceilings, ‘blow in’ insulation (such as cellulose fibre) can be an appropriate solution.
Reflective foil laminate, or sisilation, is generally installed under the roof surface and mainly resists radiant heat flow due to its high reflectivity and low ability to re-radiate heat. It relies on the presence of an air layer of at least 25mm next to the shiny surface. The thermal resistance of reflective insulation varies with the direction of heat flow through it and generally is more effective at keeping heat out in summer, though it does reduce heat loss in winter.
A range of composite materials are also now available - bulk and reflective materials are available that combine some features of both types. Examples include foil backed blankets, foil backed batts and foil faced boards.
Click here for information on how to maximise insulation performance.
Read more about insulation in the Your Home Technical Manual
The need to use air conditioners can be minimised by using the techniques outlined above. When air conditioners are used, the following points will help cut electricity consumption and running costs.
On mornings of hot days, close up the house and shade all windows to block out the summer heat. Be mindful to allow some fresh air to enter the house, preferably from the shaded (cooler) side of your house.
If you’ve followed the advice above, you will find that fans will keep you comfortable much of the time. Fans cost a fraction of running other cooling systems (well under 1 cent/hour) for most units.
The most common type of air conditioners in Alice Springs are evaporative systems, otherwise known as 'swampies'. This technology uses a large fan which blows air over filters kept damp with water from a plumbed connection. This in turn provides cooling for occupants by moving, cool moist air into the house. To ensure maximise efficiency, ensure that:
An evaporative system costs around 10 -30 cents/hour to run, depending on the fan speed and the size of the airconditioner.
Refrigerative systems, whether they be room systems (known as ‘splits’) or whole house systems (i.e. ducted) use a different principle to provide cooling that evaporative systems. They work by providing cold, dry air to lower the air temperature and lower the humidity, which in turn keeps you cool. For optimal efficiency and comfort and reduced running costs:
Refrigerative systems are the most expensive to run – smaller and efficient models cost from 10 to 22 cents/hour for each system. Larger or less efficient models (such as those common in ex-Defence houses in Alice Springs) can cost around 65 cents to a dollar / hour or more (for each unit). NB - some of these units also use a significant amount of energy in standby mode - again, the large units in ex-Defence houses in Alice Springs can use around 80 watts even when switched off.
Remember – evaporative and refrigerative systems work on different principles so to save energy and money, make sure you use each system appropriately.
No matter what system you have though, ensure that you maintain the system according to manufacturers instructions. This will help reduce running costs and extend the life of the system.
Evaporative systems should be serviced on an annual basis. Refer to manufactures instructions for appropriate maintenance instructions for refrigerative systems (cleaning the filters regularly will help keep them running as efficiently as possible).