Whole house fans (also occasionally called 'home cooling fans') are not particularly common in Australia, but are a very effective way to ventilate your entire house and force rapid air changes.
How do whole-house fans work?
Different to a ceiling fan in an attic (or an ‘attic fan’), a whole-house fan draws warm air out of general living areas and up into the ceiling space, where it's normally forced out through vents in the roof (like ridge vents and soffit vents). This in turn creates a vacuum effect lower in the house, which sucks cooler air in to your home through low-lying windows or vents. Typically, a whole-house fan is located centrally on the highest ceiling of the highest level of a house.
In order for a whole-house fan to be effective, your home needs to have operable windows and good airflow near the fan. This enables hot air to be quickly evacuated from your home. It is also suggested that you close any windows in rooms that are inhabited, to further circulate the cooled air.
How effective are whole house fans?
A whole-house fan can be a viable alternative to air conditioning, particularly in warmer climates where humidity levels are lower. In fact, according to the US Department of Energy, replacing an air conditioner with a whole-house fan can lead to a potential 30% saving in cooling costs - in some cases, whole house fans only use 1/10th of the power of air conditioning rated for use in the same amount of space.
Of course whole house fans rely on the air outside being cooler, so the cooling they provide isn't a perfect substitute for air conditioning in most cases. Having said that, whole-house fans only take a few minutes to cool your home and are very effective mechanical ventilators, providing up to 60 air changes per hour (depending on the configuration and size of your home).