Roof Ventilators, also known as whirlybirds, are wind driven turbines or impellers designed to extract the warm moist air that accumulates in the roof space between the underside of the roofing membrane and your homes ceiling.
Because hot air rises the roof ventilators should be positioned at the highest point of the roof.
I have seen so many home with these roof ventilators installed but it seems no one bothers to tell the homeowner that the installation of vents to the soffits of their homes will make the roof ventilators work more effectively….why?….let me tell you!
The air temperature in the roof void in summer can reach twice that of the outside air temperature, the roof ventilator will draw out the hot air from the roof void, if you have vents installed in the soffits, in addition to extracting the hot air from the ceiling void the roof ventilator will also pull the cooler air from the outside of the home in to the ceiling void thus lowering the air temperature in the ceiling void.
You now have cooler temperatures in the ceiling void area being moved about by the action of the roof ventilator, this will in turn lower the temperature of the ceiling material and the airspace below and reduce the amount of work your air conditioner has to do to reduce the temperature in the living area of your home.
How do you calculate how many roof ventilators you need?
Generally one ventilator per 50-60 square metres of roof space and four vents per roof ventilator will do the trick nicely!!