How effective is a whirly bird at cooling the roof?
I get enquiries very often about installing a ‘whirly bird’ (roof ventilator) to cool the house.
Whirly birds do not do any cooling.
That means they will not lower the temperature and more than the ambient.
They just ventilate.
But ventilation is better than no ventilation and if installed correctly, they can provide airflow (sucking in cooler air and expelling warmer air).
The diagram shows how a whirly bird can ventilate the ceiling space. Whirly birds just by themselves are not very effective. They require vents (either in the eaves or in the ceiling of the house) to let cooler air in as the warm air is expelled through the turbine. So, if you are getting whirly birds installed, make sure that there are adequate ceiling vents to allow air replacement.
Also, whirlybirds are less effective if you have no sarking under the roof. A closed attic space is needed to force the whirly bird to draw air through the vents. Otherwise the whirly bird will just draw air through the gaps in the roof tiles locally and not produce much cross ventilation.
So, how effective a whirly bird will be for your roof depends on what sort of roof you have…
…if you don’t have sarking under the roof tiles or a decent roof overhang to install eaves vents – then you may be wasting your money on whirly birds.
The key is in installing a ventilation system containing whirlybirds rather than just installing whirlybirds by themselves… or perhaps a different roof system.
If you want to find out more, go to this website’s HOME to start your journey.
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Update: 16th October 2013
Last week, we put in some “new’ roof ventilators on a roof in Greenacre, Western Sydney.
They were not whirly birds. These were the first “Universal Tile Ventilators” we have installed. It was an easy installation and we are waiting for the client (who sourced the ventilators himself and asked us to put them in) to give us some feedback on it’s effectiveness in providing cross ventilation to his ceiling cavity.
Update 18th October 2013
We had a hot windy day on yesterday and my Greenacre client reckons that his house is cooler due to the Universal Tile ventilators….
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