Many people think that if they have ceiling fans they shouldn’t need to have ducted air-con, but in fact this is wrong, especially if they live in a hot climate. Fans of all kinds simply move the air around. This may make you feel a bit cooler, especially if you are perspiring. But once the air becomes really hot, a fan is not going to cool you off unless you are actually wet.
We all know that hot air rises; that is why we have thunderstorms when a cool front moves in after hot weather. In the house, especially if the ceilings are high, this hot air congregates all around the top of the room. When you switch ceiling fans on, they actually push that hot air back down to the floor, so you are going to feel hotter than you were before you switched them on. Freestanding fans don’t do this.
If you have both ceiling fans and an air conditioner (and get it serviced regularly) with a high ceiling, you’ll notice it all the more because the cool air from the air con will sink to the bottom half of the room. But if you then switch on the ceiling fans, once again, you’ll feel that hot air getting pushed down. Eventually, the two will merge and equalise, but it’s far better to leave ceiling fans off, especially in weather that is scorching hot.
If you want to move the cool air around a bit more, use free standing fans that blow it sideways. That way it will disperse around the room without being compromised by that hotter layer of air towards the top half of the room. Even for those whose ceilings are not that high, it is still true that hot air rises while cool air sinks, so your coolest place will be the floor, and the coolest half of the room will be the bottom half.
The fact that cool air sinks is why most air con vents are placed high on the wall. The air from them will sink down, cooling the atmosphere on its way. However, when the air con is a reverse cycle one, the heating is not quite as efficient. You’ll probably notice that your feet get colder than the rest of your body because the hot air from the vents rises and leaves the floor as the coldest place. In this case, ceiling fans are great because they’ll push that warm air back down.
So if your home has ceiling fans, remember to use them in the winter to get the most out of your reverse cycle air conditioning. But don’t use them in the summer unless you do so without the a/c being switched on. If you have good ceiling insulation, sometimes the air in the house doesn’t get so hot, so you don’t notice much difference when those ceiling fans go on.