A whirlybird is a cylindrical dome that spins in the wind, creating a vacuum which extracts warm air from the roof cavity.
Whirly birds or ‘turbine vents’ are a type of semi-mechanical vent that can be installed on the roof of your house to help remove heat from the ceiling cavity. These ventilation systems are known for being stable, cost-effective and environmentally friendly. Whirly birds have semi-mechanical fins that spin with the wind. As it spins, the whirly bird creates a vacuum that absorbs the heat from the ceiling cavity.