Whirlybirds: What Are They, How Do They Work And Are They Worth It?

A whirlybird is a well-known roof ventilation device installed across thousands of homes in Australia.

Whirlybird installed on a metal roof

How does a Whirlybird work?

When a whirlybird spins in the wind, the cylindrical dome shape spins around creating a vacuum-type effect that sucks out all the hot air in your roof space.

Are Whirlybirds worth it?

Yes, I believe Whirlybirds work well in the Australian climate and would definitely recommend installing a Whirlybird of another type of roof ventilation device.

Why you may ask? Well, during the summer Australian roof spaces heat up quickly resulting in hot and sometimes humid heat being held up in the roof space.

Strategies such as using insulation or sisalation between the roof materials (e.g. tiles or colourbond) and the roof battens can help reflect and minimise the heat build-up, however, once the heat builds up within the roof space it’s hard to get it out without roof ventilation.

This is where whirlybirds or other roof ventilation devices come into play.  Using a whirlybird will ensure the hot air and moisture is extracted from your roof space helping you keep a cooler home.

The below video provides a great summary of the benefits of a whirlybird.

Frequently Asked Questions

During my time as a roof plumber I was often asked a number of different questions about whirlybirds – to help out I’ve documented these Q&As below.

Where do I install Whirlybirds on my roof?

When positioning a whirlybird, you want to aim to have them at the top of the roof along the ridgeline.  As hot air rises, this is where the whirlybird will be most effective at extracting the hot air from your roof.

However, if there is a particular area of your roof space that needs ventilation then you can also install the whirlybird directly over this area of the roof.

Do Whirlybirds work with no wind?

Although whirlybirds work more efficiently when there is wind, they spin in the lightest of winds.  When there isn’t wind and there is no vacuum created, the whirlybirds still help by providing an outlet for the hot air to rise and escape from.

Do Whirlybirds make your house cooler in winter?

No, Whirlybirds do not make sure the house cooler in winter.  The whirlybird only ventilates the air within your roof space, not your rooms.  Your ceiling insulation will keep the warmth in your rooms.

How much do Whirlybirds cost in Australia?

The cost of supply and installation of whirlybirds can vary depending on the roof plumber you use though you should be able to get one installed for around $300 each.`

How many Whirlybirds do I need to install?

In Australia, when I was installing Whirlybirds we used to work on an average of one Whirlybird to every 50m2 of roof space, or alternatively, you can work it based on the number of bedrooms within the house.

  • 1 x whirlybirds for a one-two bedroom house
  • 2 x whirlybirds for a three-four bedroom house
  • 3 x whirlybirds for a four-five bedroom plus house

Do Whirlybirds leak or let rain in?

No, a Whirlybird will not leak if installed correctly, nor do they let rain in.  Whirlybirds are designed in a way that the vent fins overlap each other letting air out though stopping rain from entering.

Are Whirlybirds noisy?

No, a properly installed Whirlybird should not be noisy.  If your Whirlybird is making noise then it’s like to be broken.  A common cause for Whirlybirds becoming noisy is if they’re not installed level if it’s been bent or damaged, or the bearings may be worn out.  

If you’re purchasing and installing a whirlybird yourself it’s always worth taking the whirlybird out of the box and checking it over before the installation as I have previously come across whirlybirds that have been slightly damaged during delivery.

What to do if my Whirlybird stops spinning?

If your whirlybird stops spinning it’s likely the bearings have worn out.  If this is the case recommendation would be to get a roof plumber out to inspect and either replace the bearing or install a new top section of your whirlybird (without having to remove the flashing at the base of the whirlybird)

How long do Whirlybirds last?

On average, a standard residential whirlybird will last anywhere between 10 – 15 years.

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