Print Posted on 02/03/2017

Cooling options for the home

Cooling options for the home

With some high temperatures forecast over the next week or so, you are no doubt looking for ways to keep cool at home. Thanks to Your Home, here's a quick rundown of your options to help cool your home and make life more comfortable for everyone:

Fans

With good design and insulation, fans can often supply adequate cooling for acclimatised residents in all Australian climates. They circulate air but do not reduce temperature or humidity. Typically, the air flow created by a fan provides a similar improvement to comfort as reducing the temperature by around 3°C.

Fans are the cheapest cooling option to run and have the lowest greenhouse impact; air conditioners are expensive to run and produce more greenhouse gas.

Make fans your first choice for mechanical cooling — they are the cheapest to run and have the lowest greenhouse impact.

You can also combine fans with an air cooling system for comfort at higher thermostat settings from the extra air movement. The reduced air conditioner running costs more than offset the fan energy use.


Evaporative coolers

Evaporative coolers work best in climates with low humidity as the air has greater potential to absorb water vapour. They are significantly less effective in climates with high humidity.

Some doors and windows must be open for evaporative cooling to allow hot air to escape from the house. Smaller and older units do not use a thermostat, just a fan speed control. Newer, whole-house systems can be fitted with electronic thermostats and timers.

Operating costs can be low as only the fan and a small water pump use energy. However, many units have inefficient fans and fan motors that consume more energy than necessary. Some modern evaporative coolers use far less energy than older models.

Take care when using portable units not to place them next to open windows and doors that can let in a lot of heat on a windy day.

Evaporative coolers can increase heating bills and allow a house to heat up faster when not operating, because large volumes of air can be sucked out of the house through the evaporative unit. Many modern units have automatic seals when not in use. Otherwise, close off ducts and cover the roof unit in winter to reduce heat losses.

Air conditioners/refrigerated coolers

If thermal comfort cannot be achieved with passive design, fans or evaporative cooling, consider air conditioning.

Air conditioning can give a higher degree of comfort in any climate. However, it consumes more energy and creates more greenhouse gases than fans and efficient evaporative cooling systems unless the building and air conditioner are very energy efficient.

For efficient air conditioning, the house or room should be sealed and highly insulated with bulk and reflective insulation. Windows must also be shaded from the summer sun.

Air conditioners are available as portable, wall, window, split and ducted systems. Fixed systems need to be installed by a licensed refrigeration mechanic/electrician. Ensure your air conditioner is correctly sized by having an expert calculate the cooling load before purchasing.

Ducted air conditioning units cool large areas or an entire house. Ducts must be well insulated, to at least R1.5, and joints sealed to prevent condensation and leakage. The roof should have reflective foil insulation installed and be vented to dispel hot air.

Zone systems to cool only occupied areas and allow different conditioning in living and sleeping areas.

Solar air cooling

Solar air cooling systems use a fan or ventilator to extract hot air out of the roof space for tile/metal roofs or the gap between the sarking and metal roof sheets. They work by extracting hot air from the roof space and replacing it with ambient air, to minimise heat transfer to the ceiling space below. The effectiveness of removing hot air from the roof space is very sensitive to roof colour and presence of reflective foil under the roofing. A dark (or unpainted steel) roof absorbs an enormous amount of heat. The temperature in the roof cavity is significantly reduced only by a very large air flow, well beyond the capacity of most fans and vents. A light roof or reflective foil (see Insulation) under the roofing dramatically reduces heat gain, so ventilation systems are more likely to make a noticeable difference.

Systems using a solar panel as the only source of electricity have no running costs but work only in sunny conditions. Some systems combine daytime and night-time cooling. The advantage of a system using grid electricity to power the fan is that night-time cooling can flush heat out of the building overnight.

These types of systems are many and varied. Some also draw cool/warm air into the building when required.


Cooling system operating tips

  • Shade outdoor components of air conditioners from direct sun — but don’t limit air flow around them.
  • Some units are noisy in operation. Split systems (where the compressor is outside) are quieter inside but consider your neighbours when selecting and locating external components.
  • Reverse cycle models can also be used for heating and can provide low cost, low emission heating (see ‘Heating’ above). Units that use electric heating elements cost more to run and produce more greenhouse gases.
  • For ducted systems, install a zoning system so only rooms requiring air conditioning are cooled. Ensure that ducts are well insulated and consider installing reflective foil or painting the roof a light colour and ventilating it to reduce the roof space temperature.
  • Purchase a system that has controls such as a timer to schedule activation and shut-off.
  • Set the thermostat as high as possible on your cooling system.
  • Never set the thermostat at a temperature below what you require — that does not make the unit cool faster.
  • Always aim to set the thermostat as high as possible.
  • Avoid leaving air conditioning running when no-one is home. It is cheaper to cool the house down when you arrive home, or to set a timer so that the house begins cooling shortly before people return home.