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 theory of how whirlybirds work

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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roger
4 years ago

would the bathroom ceiling ventilator would help even if switch off? or is it better to have a eaves vent? and how many vents? 2 on each side of the house? or that is too much?

Pat Robinson
Pat Robinson
4 years ago

Whirlybird and twista seem to do the same job with only minor differences. Is one more effective and better made than the other ? When being installed will the tradesman also instal eave vents ?

Jon
Jon
4 years ago

We have a house with raked (cathedral) ceilings. I am not sure of the setup of the roof (insulation etc.), but we have to rely a lot on using air-conditioners to keep the house cool. Would whirlybirds be useful in helping to expel that hot air that accumulates in our ceiling and make us a little less reliant on using airconditioners? It’s only a one-storey house as well.

Michael
Michael
4 years ago
Reply to  Jack Yuen

I have a double storey home with a large 3 storey open area with west facing full length windows. Area gets frightfully hot in summer even with window shades and double glazed coated glass. Problem is the hot air rises to the top and can’t be ventilated. We are debating between Odyssey to suck the air out or putting a fresh air filtered intake to the upstairs HVAC and run fan mode to draw in outside air (we have multiple ducted vents to the open area) interested to hear your thoughts on what’s more effective

Glenys Howard
Glenys Howard
4 years ago

We have a 30 year old cedar one storey home with cathedral ceilings in the lounge. We have whirly birds on the roof and the ceiling vents are in the lounge. It is very hard to heat the home.
Can we cover the vents so that we stop heat loss in winter.

cynthia
cynthia
4 years ago

Just found out that out bathroom exhaust fan are not connected to anything. All the steam from the bathroom released into the ceiling cavity. My question is I have someone suggested to install a whirlybird on the roof. Is this enough to remove the steam from the ceiling without connecting it to an aluminium flexible duct?

Bob m
Bob m
1 year ago
Reply to  cynthia

My son accidentally did that (vented into the attic) and I ended up having to replace the roof and a number of plywood panels above the fan exhaust rotted from excessive moisture. The roofing guy vented the exhaust fan outside the attic with a roof vent.

David higgins
David higgins
1 year ago
Reply to  Bob m

accidently? He put a fan, from the bathroom, into the roof cavity. sorry, but that’s not an accident. You wouldn’t take the garden hose, put it through an open window and then say “whoops, my bad…”

Theron
Theron
3 years ago

Hi We have a new (ish) home extension, I have noticed that the extension does not have eaves vents. The older part of the home does have eaves vents. Would installing a whirly bird in the roof of the extension still be effective ?
Thanks in advance

Nick
Nick
3 years ago

HI Jack, I am undertaking an attic conversion in a terrace house – going to install some under ceiling insulation ( 6mm kingspan) then seal up the ceiling space with walls and yellow tongue flooring – the only ventilation will be from the attic ladder – will a whirly bird work to remove the hot air build up when attic ladder trader is closed or only work when the attic ladder is pulled down leaving a “vent ” Any suggestions for his scenario ?? I have no eaves – thnx!

Stefen
Stefen
3 years ago

I have a beechwood home, it has concrete roof tiles and no sarkng.
The roof space gets at least 20C hotter than the outside ambient temperature.
i also have duced airso want to lower roof temperature and hopefully improve air con effiiency.
The roof has no eaves vents .
Ii am thinking of adding eaves vents and installing edmonds airomatic units.
My roof area is 200 square metres.
Is this a good idea or are there better ways to do it.

Justin
Justin
2 years ago
Reply to  Stefen

Hi Stefen…. did you get the eave vents installed and whirlybird/airomatic? Did you notice any difference? As I have a similar roof with concrete roof tiles with no sarking. Any feedback would be greatly appreciated.

james
james
3 years ago

I have a metal building that is used for a shop. The walls are insulated but roof is not and it is open from floor to ceiling. Would whirly birds help draw the heat from shop.

Karen Lenehan
Karen Lenehan
3 years ago

Hi Jack,
I have just got up on my tiled roof and jammed a tile in the whirly bird to stop in spinning with the belief that it will stop heat in the roof cavity escaping and therefore keep the house a bit warmer.
Do you think there is any merit in this idea?
Thanks
Karen

dick hamilton
dick hamilton
1 year ago
Reply to  Jack Yuen

um, putting the heater on would do something for keeping the ceiling cavity warm, that would be if the warm air was not being sucked out by the whirly bird. For some reason all you experts, literally all of you keep telling people whirly birds wont suck the warm air out of the roof in winter… What is there function Jack??? That is there function!!!!!!!!!!! SO yes, they will suck the warm air out of the roof Karen. You will need to design and install a way of block it from underneath. An aspect that every manufacturer and installer of these products have failed to consider or mention…. !!!!

Carolyn Richardson
Carolyn Richardson
3 years ago

Hi Jack,
We have condensation issues in our roof in the colder months. Will a whirl bird help this?

Ryan
Ryan
2 years ago

Hi Jack,

I live in a 2 storey home with no roof sparking, as I have colorbond. The roof gets extremely hot in the summer, and I have ducted aircon. What’s my best option? To instal a large whirlybird on the first floor only?

zongyi luan
zongyi luan
2 years ago

Hi, Jack:
Very appreciate you say that “The most effective way to insulate a ceiling is high quality (R rating) ceiling batts…. not whirly birds.”
Now I believe you are an honest expert.

Zongyi
who speaks Mandarin

Debbie Dunn
Debbie Dunn
2 years ago

Hi Jack,
We have a Jennings home built 11 years ago, it has a colourbond roof, with the blanket and insulation in the ceiling and walls. We live 5 minutes from the ocean. Our problem is we keep getting white mould on furniture eg wood, leather, our clothing, shoes, handbags etc. I’m spending my days cleaning, flipping furniture to spray with vinegar. I have had a bout of pulursiy 2 months ago and I’m sure it’s from the mould, and keep getting a cough that won’t go away. We borrowed a friends dehumidifier last night and placed in our walk in wardrobe and the container had about 3 litres of water in it over 16 hours, to my amazement. The humidity level was 73% when we turned it on at 9pm last night. About 6 years ago, I rang someone to come in and look to see if they could tell us what our problem was, he charged $75 did no tests and we are still living with this problem. My question is would Whirlybirds help our situation ?

Dan
Dan
2 years ago

Jack,

In December of 2018 sprinkler system piping in the attic of my 4 story condominium building froze resulting in water damage to several units. Upon investigation by a sprinkler maintenance company
consultants, the condo management company was advised to insulate exposed pipes in the attic and/or install a means of heating the attic space. Nothing was ever done.

In February of 2019 the same condo management company chose to do roof repair work in the same building in February even though they were fully aware of what happened the previous winter. The contract was awarded by the management company to a single contractor without requesting bids from other competing contractors stating that to entertain other bids would require an expense by the condominium complex of thousands of dollars. This seemed incorrect as usually any cost incurred by bidding contractors is an expense they endure as a means of winning the contract.

Furthermore IF we paid the contractor for discovery work in reviewing the disposition of the roof
the resulting findings (report) should have been the property of the condominium complex which we
could have made available to any competing bidder.

So with the contract awarded to the one and only bidder they chose to open the roof in the middle of February without doing anything to protect the attic sprinkler piping and while outside temperatures were in the single digits! Furthermore during this time they also installed on the roof
six, four feet tall non-powered whirlybird ventilation units.

Well the pipes froze and 30 units got flooded. I am not living in my condo at the moment having been forced to leave while repairs are made. I believe that the management company is in cahoots with the contractor and the whirlybirds (which mysteriously have since disappeared from the roof having been replaced by fewer smaller units) were deliberately put in place to cause the failure.
And not only did this happen in one building but it actually happened in two buildings within an hour or so of each other.

I would appreciate your opinion on the possibility that this was deliberate.

And as you probably could have guessed the management company has chosen the same contractor potentially negligent in the roof work to be the contractor to do all the reconstruction work internally!

Again, I would appreciate your opinion on the possibility that this was deliberate.
I and several other owners are considering legal action as the management company has provided little in the form of restitution of any kind throughout this entire ordeal.

Thank you,

Dan

julie
julie
2 years ago

Hi Jack,
I have a two story cathedral ceiling house, exposed beams, no insulation and the entire west facing wall is glass – it is unbearably hot in summer!
We are considering enclosing the beams and installing insulation but this will be expensive and lose the character of the house. Alternatively would whirly-birds remove the heat and are the ok to use in cathedral exposed beam ceilings?
Any advice would be appreciated
Thanks
Julie

Batwam
Batwam
2 years ago

I agree with the skylight/velux solution and recommend a system with automated closing (rather than manual) which can be left open during the day to ventilate without having to worry about it staying open if it starts raining…

This said, based in my experience, this won’t be sufficient as it doesn’t block radiated heat. Put as much insulation as you can between the beams and enclose the gap if you actually want to fix the issue.

Matt Jones
Matt Jones
1 year ago

Hi,

We have a flat metal colorbond roof that has metallic insulation on the underside of the roof. There is little or no insulation on the ceiling side. It has a large roof space and we have 3 whirlybirds installed. Are we losing a lot of heat in winter time?

Cheers,
Matt

Dave Jordan
Dave Jordan
1 year ago

Hi Jack. Do you have an opinion on the difference between powered roof ventilators or just whirly birds

Paul Joswig
Paul Joswig
1 year ago

Hi Jack, thanks for all your assistance to people here, and I hope you can assist me as well. 🙂

I have thought up a plan for my roof cavity ventilation, and I am wondering about your thoughts.

I am thinking of using ducting and inline fans, rather than whirly birds. I would create eave vents to allow air in, and the ducting would start high in the roof cavity and end at other eave vents.

The idea being to use fans to suck the hot air from high and expel out the eaves.

Reasons: we have solar, and so it avoids potential shadowing from whirlies, as well as erratic performance, and sucking air out when we don’t want it to (I.e. cold days). The fans will easily be powered by the solar when it’s hotter months, so no running costs.

What do you think?

Also, what are your thoughts on capacity… E.g. how many times per hour should we be looking at exchanging the roof cavity air?

Atm I am thinking of two fans at separate ends of the house, but it’s Just a guess that’s it’s enough or necessary.

By the way, a separate project is to duct the two bathroom fans and the stove exhaust fan to the eaves as well. At present they exhaust to the roof cavity.

Thanks and regards
Paul
Adelaide SA

Keith Edward Tupper
Keith Edward Tupper
1 year ago

We have had our Breezair unit serviced, partly because we thought it may be responsible for the continuous knocking sound coming from the roof on a windy day. The service man told us the unit was sound, and would not be responsible for the knocking sound. But he told us we have a whirly bird (having moved here five years ago we were unaware of this, as it is completely out of sight from ground level), and that may be responsible, although as far as he could see it was all right.
Can you throw any light on this?

Anthony Kayondo
Anthony Kayondo
11 months ago

Hello,

What is the best way for cooling a concealed roof on a bungalow house with a single pitch. The single pitch angle is quite small and there is a gypsum ceiling(We don’t have winter where I am). The heat is excessive in the ceiling area. We put louver ventilators but their design bars proper air flow to cool the ceiling area. Will the whirly birds be of any help?

Colin
Colin
6 months ago

Hi Jack

I have an old house which recently had roof leakage and mold have developed inside the house, would a whirly bird be helpful in keeping the ceiling cavity dry and hopefully prevent mold buildup?
Thanks

Muhamed
Muhamed
9 days ago

Hi, I hope somebody can help me. We have a house that has concrete roof tiles and no eves. The roof space gets very hot in summer. I would like to put whirly birds or something similar for now until I get ceiling insulation installed in the future. What can I do? Thank you in advance

Muhamed
Muhamed
6 days ago
Reply to  Jack Yuen

Hi Jack, thank you very much for your response! I think that’s the way to go. I was thinking if I did put whirlybirds, maybe I can but ceiling vents in a few areas of the house but if you think it’s not worth it..