Active cooling is cooling that needs power. In the old days, it was beautiful slaves fanning the master with Ostrich and Peacock feather fans. There’s not many slaves around nowadays, nor Ostrich feathers, so we’ll have to make do with electricity.
All of the passive techniques covered above can increase your comfort level and reduce the amount of power that you use but there are still many times when you’ll need to use a powered appliance.
We’ve also a page on using your garden to cool things down a bit.
Ceiling and pedestal fans
These are the most common fans and cool you by blowing air around the room and across your body. As it evaporates your sweat, it cools your skin.
Pedestal fans work well and are very cheap, but by far the best are ceiling fans. They can be expensive to buy and have installed (they need a certificate of compliance from a licensed electrician) but do an amazing job.
Installing them in all of the most commonly used rooms in the house – lounge, kitchen and bedrooms raised the temperature at which the rooms became uncomfortable by up to 6 degrees. This meant 6 degrees that we don’t need the air conditioner on for, saving us heaps of energy and money.
The fans in your kitchen and bathroom can be used to cool your home. Used when the outside temperature is below that inside the house, they can literally suck the heat out of your home and the cool right in. The job they do will depend on their position but by creating negative pressure inside the house, they cause the cooler, outside air to flow in.
If you can add draught stoppers to your exhaust fans. These are two piece plastic chimneys with a flap. They go over your exhaust fan, up in the roof cavity. When the fan is on, the flap lifts to allow the vented air to escape. When the fan stops, the flap drops and seals off the device and stops hot air from coming in (they’re also great for keeping dust out).
Because of the way they’re manufactured, you don’t need to go up into the roof space to install them. All you do is pop out your exhaust fan, slide the two pieces up through the hole in the ceiling and clip them together. Then you reinstall the exhaust fan and away you go. No more dust or hot air.
Old exhaust fans can us a lot of power for the short time the’re in use. Those that I removed from here averaged 80W each! I replaced them with low energy fans from Arlec that draw, around 4W each. Their flow rate is lower than the old style fans but their power consumption means that you can have them on for longer and still use less power.
If you’re replacing exhaust fans with low energy models and adding draught stoppers, make sure the draught stopper is light enough to be opened by the pressure from the fan. Some models are a bit too stiff at the opening and won’t open.
In many cases, you won’t need an electrician to upgrade to low energy exhaust fans. Many houses have a plug in the roof cavity where you can unplug the old fan and plug the new one in.
There are two types of air conditioners – evaporative and refrigerated.
Refrigerated air conditioners (or heat pumps as they’re called in some parts of the world) work like your refrigerator. A coolant fluid is circulated through the unit. This picks up fluid heat in your room and uses that energy to expand. It is then pumped to a cooler area (outside) where it is compressed (by a compressor in the unit) and gives off the heat where it is blown away by a fan.
These are often in one room only where they work well but usually don’t extend to the rest of the house unless you have a fan blowing the cold air out of the room and into another. Bigger and more expensive units are ducted throughout the house.
Evaporative air conditioners are those roof mounted boxes that you see on many houses. They pump water (which is usually cooler than the air) over pads of a straw like material. They have a fan which draws air over and through these pads where the water cools it, The fan then blows it into the house.
These are usually ducted throughout the house. The moist air can cause the humidity to rise quite a bit and they’re not terribly efficient when the temperature is very high and/or the water in your pipes has got bot from the weather. They also use water which is run off through a valve and if your’e not careful, can run away down your drains.
It’s not terribly difficult to catch this water or redirect it to a tank or directly onto the garden.
There are many portable units available that work on this evaporative principle. They come in many shape, size and complexity and usually benefit from having ice water or just ice added to their water reservoir.
These portable units do have a drawback though. They can make the humidity of the room uncomfortably high very quickly. I remember the one we had when I was growing up. It was great for an hour or so then everything got tropically sticky.
Evaporative air conditioners work best if you have a window or two slightly open to allow the air to flow out. This makes it more effective on your body and helps reduce the humidity.
We use our evaporative roof unit at night or early in the morning when the outside temperature is lower than that of the inside. It has a ‘vent’ function that doesn’t cool the air with water, it just pumps outside air into the house. We open all the doors and windows for an hour or two and use the cooler, vented air to push the warm air from the house. This technique saves power and water because there is no water pump running in the unit.