How Melbourne's summer suits an evaporative cooler
Mostly moderate humidity
Melbourne Airport averages 44% afternoon relative humidity in January and 45% in February (Bureau of Meteorology, 1991 to 2020). Melbourne's summer dewpoints range from 9.5 to 11.7 degrees in the same tables. That's not desert-dry, but it's dry enough on most hot afternoons for evaporative to do its job.
Sticky days do happen
The city's record high dewpoint, 24.0 degrees, was set on 30 December 2016. On a day like that, Seeley says the air already holds too much moisture for evaporation, so a cooler can only move air around.
The north-westerly
Hot north-west winds build ahead of a cold front, sometimes at gale force, until cool south-westerlies off the Southern Ocean push the desert air out. That hot, dry wind is exactly the weather evaporative cooling is built for.
Hotter away from the bay
Suburbs inland run warmer: January's mean maximum is 28.2 degrees at Viewbank in the north-east, against 25.0 at Mornington on the southern coast. The hotter the house, the more outlets and airflow it'll need.
Evaporative or refrigerated for a Melbourne house?
Evaporative brings outside air in through wet pads and pushes it through the house with the windows open. Reverse cycle runs with the house closed up, copes with humid nights, and heats in winter too. If you already have gas ducted heating and want cooling through the same ducts, add-on cooling is a refrigerated option, not an evaporative one.
In the 2021 JWS survey, 23% of the home owners had ducted evaporative and 18% ducted reverse cycle, so both are well known here. Our evaporative or refrigerated guide goes through the trade-offs.
What to settle before the roof unit goes up
Where it sits, relative to next door. EPA Victoria says an evaporative cooler mustn't be heard inside a neighbour's habitable room after 11pm, or before 7am on weekdays and 9am on weekends and public holidays.
How it's fixed down. Lysaght's wind guide gives a hilltop house in Melbourne's suburbs wind region A, class N3, and the north-westerlies can blow hard. Ask how the unit and its roof opening will be secured.
Where the air goes out. Seeley says the cooled air isn't recirculated, so windows or doors on the far side of the house must be open, or security vents fitted instead. An evaporative specialist will plan that as carefully as the roof unit. The national evaporative cooling page covers the install itself.
Renting out a home with evaporative cooling
Consumer Affairs Victoria says a ducted evaporative cooler that fails and can't be repaired can be replaced with another ducted evaporative cooler with an outlet in the main living area, or upgraded to a compliant fixed cooler. From 1 July 2030, every Victorian rental must provide fixed cooling.
What you can do on a hot Melbourne afternoon
You can
- Open windows or doors on the far side of the house from the vents before you switch on.
- When the cool change comes through, switch off and let the outside air do the work.
- On a muggy day, use fan-only mode, or run it early in the morning or late in the evening, as Seeley suggests.
- Sort winter heating as a separate job.
Leave to a licensed installer
- Cutting the roof opening and fixing the unit down.
- Ducts and ceiling outlets.
- Water, drain and power connections.
- Setting the bleed rate.
Questions to ask a Melbourne evaporative installer
- How will the unit be fixed to the roof to handle a strong north-westerly?
- Where will it sit relative to the neighbours' bedrooms?
- How many outlets, and will the hottest rooms get enough air?
- Which windows do we open, and would security vents suit us better?
- Would refrigerated cooling, or add-on cooling on our gas heater, suit this house better?
What we'd do
If it were our Melbourne home
If we already had gas ducted heating and wanted fresh, open-window cooling for hot north-wind days, evaporative would be a sensible fit. If we wanted to close the house up on muggy nights, or have one system for winter too, we'd go reverse cycle. Either way, we'd want an evaporative specialist to plan the exhaust windows and the roof fixing, not just pick the unit.
