Where a whirlybird should go
High on the roof, close to the ridge, where the hottest air collects and the wind is strongest. A whirlybird low on a slope or tucked behind a second storey spins less and moves less air.
Spread them along the roof rather than bunching them, and keep them clear of the back slope where neighbours' houses or trees block the wind. The roof also needs somewhere for air to come in, usually eave vents, or the whirlybird just spins without shifting much.
Fitting one to a tile or metal roof
On a tiled roof, the roofer removes a few tiles and fits a base with a flexible or lead flashing skirt dressed over the tiles around it. On steel sheeting, the base is cut and shaped to match the sheet's profile, then screwed and sealed so water runs around it.
The base is what keeps rain out. A whirlybird sitting on a generic base with a bead of silicone around it is a leak waiting to happen. Ask what base the roofer is using and whether it's made for your roofing.
Solar whirlybirds
A solar whirlybird adds a small solar panel and motor that keeps the turbine turning when there's no wind. It's useful on still, hot days, which is when a roof space is hottest and a wind-only whirlybird slows down.
They cost more than a standard whirlybird, have a motor that can eventually wear out, and only help in daylight. Bradford says its wind-driven vents still draw some air on still days through the stack effect (hot air rising on its own), so for most homes, well-placed standard whirlybirds with good eave intake do the bulk of the work.
Signs a whirlybird needs attention
- Squealing or grinding when it spins, usually worn bearings
- A turbine that wobbles, leans or has stopped turning in a breeze
- Water stains on the ceiling under or near it after rain
- Dents or bent fins after hail or a storm
- Rust around the base on a metal roof
What you can check from the ground, and what's a roofer's job
You can
- Watch from the yard on a breezy day to see whether each whirlybird spins freely
- Listen for squeaks from inside the house
- Check ceilings near the whirlybirds for stains after heavy rain
Leave to a roofer
- Installing, moving or replacing whirlybirds
- Replacing worn bearings or the turbine head
- Fixing a leaking base or the tiles around it
- Fitting eave vents so the whirlybird has air to draw
What we'd do
We'd fit standard whirlybirds high on the roof with matching eave vents, and only add a solar model on a roof space that still bakes on still afternoons. On a squeaky one, we'd ask the roofer to replace the head rather than the whole unit, as long as the base isn't leaking. Choose the roofer who asks about intake before they talk about how many whirlybirds to sell you.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.