On one hand they can be amazing. Free cooling during summer. Casting flickering dashes of light onto the floor below. Making great use of the phrase “hot air rises*”. But like they say, “there’s no such thing as a free lunch**”. We’re talking roof turbines people – those 70’s inspired spinning domes on our roof.

The lunatic whirly-bird!

So here’s the thing. These turbines care not if it’s summer or winter – in fact the freezing gales of wind that blow in winter serve only to make these turbines work harder. And therein lies the problem. They suck no matter the weather or the temperature.

In summer they remove the hot air that fills your roof cavity or the top of your room if you have pitched ceilings. This either cools the room or increases the thermal insulation in your home. Magically this equals free cooling and zero emissions. Nice.

In the cooler weather this becomes a huge issue. Your central heating works hard against the elements, trying to emulate a beautiful spring day inside while the sleet sweeps in outside. Then in comes the lunatic whirly-bird on the roof sucking all of the toasty warm air out of the home, leaving you with huge gas bills and an overworked heater.

Say it ain’t so I hear you exclaim. Well here’s the math. According to one manufacturer their 12” model, in 8km/h wind (not too strong), will move just under 10 cubic meters of air per minute. Consider an Olympic size swimming pool contains, roughly, 2500 cubic meters -the 12” roof ventilator would shift that swimming pool chunk of air in 4 hours. And this is air that you’ve paid to heat up.

What can you do?

For those of us with a pitched internal roof you’ll be able to, carefully***, grab a ladder and take a peak at the vent in your ceiling. In most models there should be a disguised knob on the front that can be turned. This will lower a couple of louvres that prevent the flow of air in and out of the turbine. Job done. Energy saved. Just don’t forget to open it up again when summer starts up.

If you’ve got a non-pitched internal roof you probably don’t need to worry because the vents will be above the ceiling. The better insulation in the roof space will keep you nice and toasty.

So there you have it.

Roof turbines are a mixed blessing. Great in summer. A pest in winter. Safely get up and have a peek to see if your turbine can be closed in the cooler months. It could save you big dollars and reduce that carbon footprint. Sweet.

* Although conspiracy theorists will deny it, hot air does not rise. It’s the more dense, cooler air that falls causing the hot air to be displaced upwards – semantics I know.

** Free lunches are available from the nearest wedding reception. Getting caught, however, is frowned upon. You have been warned.

*** If you are uncoordinated, like me, get the stunt-man or athlete in the family to do this. You’ve been warned.

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