By taking steps to keep the heat out of your home, you can maintain a comfortable temperature while using your cooling system more effectively to reduce costs over summer.
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Active cooling systems such as fans, evaporative coolers and air conditioners play their part when cooling a house, but passive techniques that focus on windows, draught proofing, ventilation, insulation and landscaping can reduce energy consumption and be instrumental in keeping a house cool during the heat of the summer months.
Optimising your home for passive cooling will greatly reduce your reliance on active systems, helping to reduce costs and ensure your home is more resilient to extreme temperatures.
The ability to cool down your home in summer and reduce your energy consumption and costs is affected by 5 key factors.
Insulation is the most effective way to improve the comfort and energy efficiency of your home. It greatly reduces heat entry through building surfaces in summer, and greatly reduces heat losses during winter.
Installl insulation on your ceiling, in walls and under suspended timber floors to create a sealed envelope which acts like a thermos in winter, keeping the warm air inside, and an esky in summer, keeping the cool air inside.
For summer, it’s important that insulation is used in conjunction with good shading for west, east and north windows, otherwise you risk creating a hot box by trapping radiant heat from the sun (sunshine) that enters through large unshaded windows.
2. Window design, orientation and coverings
Windows can let a lot of heat into your home during summer, especially if you have large west, east and north-facing windows that aren't adequately shaded. The radiant heat from the sun (sunshine) passes easily through an unshaded window and can quickly put a lot of heat into your home. If your home is well insulated, this can trap the heat and create a 'hot box.'
Fortunately, there are simple steps you can take to reduce heat gain through your windows. Use of external shading is best as it stops the sunshine before it hits the window, but even internal shading can reduce heat entry to some extent and improve comfort.
3. Draught proofing
Draught proofing, or sealing up gaps and cracks, will minimise the amount of hot air entering your home on summer days and reduce your cooling bills. It also prevents heated air escaping from your home in winter, reducing heating bills.
Sealing gaps around doors and windows is a cost-effective way to ensure your home is more comfortable and is a relatively easy upgrade to do yourself.
For summer comfort, it’s important that good draught proofing is combined with good ventilation – you want to keep hot air out during the day but allow cool air in at night or after a cool change.
Ventilation is also an important way to regulate your home's air temperature in summer and keep it free of condensation build-up, which can result in mould, rot or damp in winter. Once the temperature starts to drop in the evening, or after a cool change, it's important to open your doors and windows to flush warm air from your house and allow cooler outside air to enter. The benefits are likely to be greatest if you open doors and windows facing the breeze and also doors and windows on the opposite side of the house.
Careful selection and
positioning of plants can provide summer shading and act as a buffer against
hot winds. Tall, deciduous canopy trees provide shade to north windows while
still allowing the lower winter sun through. Smaller, deciduous shrubs are
useful for shading east and west windows and walls. Deciduous creepers over a
north-facing pergola will provide shade for windows and walls.
Use of insulation, shading, draught proofing and ventilation, all passive cooling techniques, can keep your home comfortable on all but the hottest days, minimising the amount of active cooling you need to use and reducing your summer energy costs. Fans provide a low-cost form of cooling that can also reduce the need to turn on air conditioners and evaporative coolers.
If you have an air conditioner or evaporative cooler, choosing an efficient model and using it efficiently will help to reduce your summer cooling costs even further.
Ceiling, wall-mounted and portable electric fans can be a cheap and effective way to stay comfortable on warm, humid summer nights. Fans are inexpensive to purchase and can cost less than two cents per hour to run.
Although fans do not reduce the air temperature, when used in conjunction with your air conditioner or evaporative cooler they can reduce the need to use your cooling system. Fans help to keep you feeling more comfortable without having to operate your air conditioner at lower temperature settings.
Fans can also assist with natural ventilation, helping to move air through your home.
Air conditioners extract heat from the air inside your house and transfer it outside, cooling the air to a temperature determined by a thermostat. They are available in portable, room and ducted systems. Reverse cycle air conditioners can also be used to efficiently heat your home in winter, meaning they can keep your home comfortable year-round.
The following tips will help to ensure you are getting the most out of your air conditioning system.
Keep windows and doors closed
Keep them closed when the system is operating to avoid wasting energy by letting cold air escape and warm air in. If using a room air conditioner, ensure the door to the room you are cooling is closed.
Minimise the area to be cooled by zoning
Use the thermostat correctly
Use portable and ceiling fans wherever possible – they are much cheaper to run than air conditioners and can also be used in conjunction with your air conditioner to circulate cool air and make you more comfortable when operating the air conditioner at higher temperatures.
Don't leave your air conditioner running
It’s a myth than running your air conditioner 24/7 will give lower running costs. It is far cheaper to turn the air conditioner off while you are out of the house or overnight while sleeping, and on again when you return or after the house warms up during the day.
A fan will generally keep you comfortable during warmer nights and will cost far less to run. Use the economy setting if your system has one – this setting reduces energy use by maintaining moderate rather than cold temperatures.
Use a timer or programmable thermostat
Some air conditioners have in-built timers or programmable thermostats that allow you to control the time the system turns on and off, and in some cases to adjust the thermostat setting. You can use these to turn the system on a half hour or so before you come home so that it is comfortable when you arrive, and to ensure that it is switched off overnight.
If you have a rooftop PV system that is exporting a lot of electricity during the middle of the day, you may be able to switch on the unit for a few hours during this time to pre-cool your home with this cheap electricity, reducing the need for cooling later in the day. Pre-cooling will be most effective if your home is well shaded and insulated.
Keep and let in cool air
Utilise rooftop PV
If you have a rooftop PV system, this can be exporting a lot of electricity to the grid during the middle hours of the day. If your home is well insulated, free from draughts and contains some thermal mass, you can time your air conditioner to pre-cool your home during the middle of the day and maximise self-consumption of energy generated by your rooftop PV system.
A well-designed home will remain cool and enable you to use your home like a battery, utilising energy while its free to maintain comfort into the evening.
Shade the compressor unit (heat pump)
If the compressor unit (the part located outside) is exposed to full sun during the day, shade it with an awning, shade mesh or a similar structure. Be careful not to restrict air movement around the unit. Ensure the heat pump is installed as per manufacturer’s instructions and is not too close to the wall or fences. Be careful not to store items in front of the unit.
Turn the system off when you go on holiday
Don't forget to turn the entire system off at the switchboard completely when you go away on a holiday.
Maintain your air conditioner
Evaporative cooling systems draw air through a moist filter pad, cooling and humidifying the air before it is blown through your house. They are available in ducted, wall-mounted and portable units, and work best in dry conditions. Evaporative coolers are less effective in extreme heat and on humid days and are not well suited to humid climates.
The following tips will help to ensure you are getting the most out of your evaporative cooling system.
Open doors and windows
To work effectively, evaporative coolers must draw air through a moist filter pad and blow it through the area to be cooled to outside the home. Ensure that doors and windows are kept open in rooms being cooled, and that the opening is large enough to allow the air to flow freely outside. Having insufficient openings will reduce the cooling effectiveness of the unit and may put too much back pressure on the fan.
Operating an evaporate cooling system with doors and windows closed can force moist air through gaps and cracks in the home and cause issues with a build-up of moisture.
Open opposite doors and windows
Reduce heat gain by opening windows and doors on the opposite side of the house to the hot prevailing winds where possible.
Use a low fan speed if possible
The evaporative cooler’s fan is responsible for most of the electricity consumption, and the higher the fan speed the higher the more electricity is used – if you double the fan speed, you will increase energy consumption by a factor of eight!
While you might use a higher fan speed when you first switch the cooler on, reduce this to the lowest fan speed that allows you to feel comfortable once you have vented the hot air from the room.
Adjust for humidity
On days of high humidity when it’s not too hot outside, turn off the water supply to the cooler and run the fan only. This can be quite effective on still, humid evenings when the outside air has cooled down.
Prevent air leakage in winter
Ducted evaporative cooling outlets can be a significant source of heat loss in winter. Special covers are available which can be fitted over the outlets and rooftop unit in winter to reduce heat loss through the ductwork. Not winterising your evaporative cooling system will make your home cool and draughty, and significantly increase the cost of staying warm in winter.
Maintain your evaporative cooler
Evaporative coolers should be regularly serviced and maintained in accordance with manufacturer's instructions to keep them operating effectively. Water stagnating in the system, especially over winter can lead to issues with mould, which when in use can have negative health impacts. These issues will not occur in a properly maintained system.