What is that new thing on the roof? Just to the left of the solar panels is our new evaporative air conditioner, installed 2 days ago in the middle of a Perth run of hot weather, with maximum temperatures running over 34C for more than a week now.
This post is about our decision to choose the evaporative air conditioning, after deciding that the passive heating and cooling measures we had taken already in retrofitting our house, needed amendment for the changing climate. See our post about it here
I am not sure that everyone understands evaporative air conditioning and how it works. An evaporative air conditioner uses the natural cooling properties of water to lower the temperature of a room through evaporation. A ducted cooling unit is installed on the roof and connected to a series of outlets throughout the home that draws in fresh air from outside.
The hot air passes through filter pads located inside the roof unit which cools the air and then distributes it through the vents inside your house. With an evaporative air conditioner, the entire volume of air within the house is refreshed every few minutes.
Evaporative air conditioners work best in Perth on days when the air is hot and dry. So essentially, the hotter the air, the better the cooling effect will be. We have LOTS of these.
Benefits include the use of fresh air to cool the home, and the ability to have the windows open! It is low in energy use compared to refrigerated air conditioning. We have noticed that because it operates with open windows, the patio outside our kitchen is also feeling the benefits of the cool air. This would not happen with refrigerated air conditioners, which rely on keeping windows closed.
Of course, if the weather is humid, the evaporative air conditioning does not provide much assistance. Compared to the east coast of Australia, where they have summer rain, Perth does has a mediterranean type climate with a summer drought, so evaporative air conditioning has more application. In fact, we estimate about one third of the houses in our suburb have evaporative air conditioners visible on their roof.
When the water has been used for cooling, it runs down a pipe to this bin which is on the side of our house away from the entrance, and from there we run it over to our struggling lemon tree. I am hoping the extra water will cheer it up!
Comparing the cost of a whole of house evaporative air conditioner and a whole of house heat pump type air conditioner, the evaporative is much cheaper. We could have chosen a split system to cool the bedrooms -because being too hot overnight is a really difficult thing, if you want to sleep- or the whole of house evaporative airconditioner. We choose the option which would give more comfort for us wherever we were, for the amount of money we could afford at this time.
What will we do if it is humid, and evaporative airconditioning is not an option? The system can be operated without the water, as a fan, but I reckon we would rever to the way we did things before -closing the house during the cool of the morning, using our ceiling fans, and waiting for cooler temperatures overnight. We still will have had many more comfortable days than we did before.
There is still the option for a heat pump -especially a split system for the bedrooms -at some later date, if we so choose.
How has it been so far? It has made an astonishing difference. It feels cool in here, and we have more energy for living life. I am even happy to turn on the oven and cook in the middle of the day!
