# Forum Home Renovation Heating & Cooling  whirly bird, any difference betwwen them?

## wozzzzza

im thinking of getting 2 whirly birds for my roof, if there any difference between getting a all metal one and getting a clear top one?
what one would you get and why??

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## parlyboy

> im thinking of getting 2 whirly birds for my roof, if there any difference between getting a all metal one and getting a clear top one?
> what one would you get and why??

   Hey waz 
I looked at getting one but got ducted evap cooling instead. I preferred the look of the clear ones as i assume they let more light in.
I assume this is to get hot air out of your roof?

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## wozzzzza

yeah man, get hot air out of the roof as its like 65 degrees at the peak when i measured it last on a hot summer day. cant be doing things any good at that temp, also the humidity from bathroom fans etc.. plus the temp its putting through the insulation making the house hot.
i figure that if i can get that hot air out it will help the aircon and keep house cooler all going well.
and with that clear ones, im wondering if its a good idea to let more light in or not.

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## parlyboy

> yeah man, get hot air out of the roof as its like 65 degrees at the peak when i measured it last on a hot summer day. cant be doing things any good at that temp, also the humidity from bathroom fans etc.. plus the temp its putting through the insulation making the house hot.
> i figure that if i can get that hot air out it will help the aircon and keep house cooler all going well.
> and with that clear ones, im wondering if its a good idea to let more light in or not.

  65 degrees...holy moly.  :Yikes2:  
I hate sticking my head up there, not sure what im looking for anyway. 
Ive heard they can take at least 8 degrees out of the roof, possibly more. Not sure where i heard that from though.
Maybe a disadvantage would be in winter, when you actually want to keep the heat in.

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## Groggy

More light in equals more heat, I wouldn't do it if heat is a problem. 
Regarding the whirlybirds, Why only two? You need enough to exhaust the heat generated by the tiles. You also need to install vents in the eaves to allow cool air to be sucked into the roof cavity. Up to four whirlybirds and seven or eight vents (depending on size of the roof) would not be unrealistic.

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## nww1969

I have two whirly birds and eave vents and does not do much. 
Im looking at setting up a 12volt fan system to suck air in from the eaves and maybe
another in the whirly vent to help suck the hot air out. 
Would like to connect these to a solar panel so no extra costs.  
There is a few systems where there is a vent with blower but trying to get a price from 
manufacture is almost impossible.

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## murray44

I assumed the clear top ones were a combined whirly bird and skylight/light tube thingy.

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## wozzzzza

> There is a few systems where there is a vent with blower but trying to get a price from 
> manufacture is almost impossible.

   hundreds of dollars, ive enquired, about $400  and im not going to have one running off the power point all the time chewing power.

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## Gravy258

they sell solar powered roof vents.
general consensus on whirly birds is there useless
Re: latest issue of the ATA magazine (alternative technology association) 
What you want is reflective foil insulation on top of the bulk batts. 
gravy

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## manchild

Why would a whirlybird that drops the temp inside the roofspace be useless?Ive been in and out of roofs for 19 years now and i know which roof i would like to be in.However i seen so many poorly positioned installations that is not funny.Eavevents not installed properly if at all ,whirlybirds in the 4th row from the bottom,no inside vents in cathedral ceiling so on so forth.In winter when you put your heater on water condenses on the top of the batts and all around the roof cavity ,whirlys prevent that.Just food for thought .
George

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## Shubes

Just to add some more food for thought, as I'm currently looking into this myself... 
I recently had my roof insulated, and I got chatting to the installers. I asked them what they thought of whirly birds (since all they do all day/every day is climb in roof spaces), and they love them. They said they feel a massive difference in temps in roof areas that have them fitted. 
I think the key is making sure they are installed correctly, in the right locations, and with appropriate eave vents. For a small house, one bird is enough... the bigger the house gets, the more birds you need. Apparently the location of the vents can have a big impact on creating/controlling the flow effect. I can't remember what he said exactly, but a staff member at Bunnings told me the ideal location for vents is on certain sides of the house - I THINK it was South and East to be most effective, but I can't remember. 
As for the clear ones - I would stay away from them, unless you want to use it as a skylight too. Otherwise it's just letting more heat in during Summer time. 
Interesting about the Winter thing too - I've heard good and bad. Some people say they block them up in Winter (ie. throw a bag over them), to stop heat escaping, whereas other people say they work well in Winter at controlling condensation etc..... and can make ceiling insulation work more effectively. It'd be great to see someone do some proper testing, I'd love to know. 
Either way, I will be installing a full metal one very soon. It's sitting in the box in the shed - project number 695 on my list  :Wink:

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## Pulpo

Its interesting that I have been told they are useless too but my experience would suggest otherwise. 
I have two gathering dust waiting to be install on the shipping container. 
Roofing plumber told me to get metal bearing such as spinaway. 
Also install one of the below.  Windworker - Consumer Need 
[URL="http://www.windworker.com.au/consumerNeed.html"] 
Pulpo

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## andy the pm

I guess the main disadvantage of whirly birds is they don't work when there is no wind....
As for location I would assume as high up as possible and on the side that faces the prevailing wind. 
I think I'll end up sticking the solar power ones in, or look at the cost of applying heat reflective paint to the roof. 
Andy

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## manchild

> I guess the main disadvantage of whirly birds is they don't work when there is no wind....
> As for location I would assume as high up as possible and on the side that faces the prevailing wind. 
> I think I'll end up sticking the solar power ones in, or look at the cost of applying heat reflective paint to the roof. 
> Andy

  Whirlys work with the rising heat in the roofspace not the wind.Go check out some in the neighbourhood on a very still summer morning.You will see the ones on the shaded roofs are still and the ones on sun would be already working.
cheers
George

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## NigeC

The difference between the inside of my roof without the whirlybird and the inside of my mates roof with the whirly bird is unbelievable. In testing, both were hot days and mine was like a sauna where as his was quite barmy.
Almost made me want to put on in until I saw the price at Bunnings

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## jonb

Check out Envirotalk Australia | Whirlybird Myth Exposed - Forums for a detailed explanation as to why they don't work.

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## dib

That article doesnt say it doesnt cool the roof space, just that it doesnt make a big difference to the house temperature if you have ceiling insulation, and there are other things to do to get bigger bang for your buck. 
One thing it doesnt take into account when the cold water supply is through the roof space.  On hot days the cold water can be as hotter then hot water typically is.  I have read articles about the cold water being hotter than the tempered hot water.

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## jimbob

With all the talk on the whirlybirds, I installed one some time back, I live in the tropics so we get real rain, 300 to 500ml overnight is common in the wet season, we also have 35 degrees plus days, thats the air temp, not the roof temp. There are vents all around the house to the ceiling space. When we cut the hole the the superheated air rushing out just about ripped my face off. Since then it has aired and cooled that space and never leaked. My conclusion is they work, (well).

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## president_ltd

> With all the talk on the whirlybirds, I installed one some time back, I live in the tropics so we get real rain, 300 to 500ml overnight is common in the wet season, we also have 35 degrees plus days, thats the air temp, not the roof temp. There are vents all around the house to the ceiling space. When we cut the hole the the superheated air rushing out just about ripped my face off. Since then it has aired and cooled that space and never leaked. My conclusion is they work, (well).

  they work for you because "*there are vents all around the house to the ceiling space*". 
if you have insulation on your ceiling, with those vents into the ceiling cavity, you may as well not even have ceiling insulation - no wonder it gets hot (and no wonder the whirlybird or even just the ability to 'vent' your ceiling cavity works. 
but if your ceiling cavity was sealed (no airflow) from inside your house living area and had appropriate insulation between the two, the heat buildup in your roof space would not equate to equivalent heat build up inside your living area.

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## alanhc

There are many misunderstandings regarding effectiveness of whirlybirds and alternative roof ventilation devices. They are designed to move air from the ceiling space, or rooms if connectd via suitable tubing. Their effectiveness is actually how well they move the air. Insulation will determine temperature effects below the ceiling to a great extent. Unless replacement air can easily enter the vented space, their operation may be suboptimal. The measured comparisons shown at the link below may serve to indicate how/why some are superior to others. Environmental Sciences Australia
(follow the link above the pictures to view comparisons within the report).
The operation of the non-whirling, Wind Directional Skylight Vent can be viewed in a short video (from The New Inventors) on the home page of the site. Due to the very open nature of this vent, on days with minimal wind the hot air can still exit and will do so with far less obstruction than with a comparable whirly style.
Finally, in many instances the removal moist air is a very beneficial action of vents, especially in the cooler months when condensation can occur within the ceiling space and in poorly ventilated rooms (bathrooms, kitchens).

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## r3nov8or

This page suggests the clear ones are to allow natural light into the roof space. Planet Green - Specialising in whirlybirds, roof ventilation, vents and much more ... 
I imagine there are versions that also double as a vented skylight into the room below?

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## petersemple

I have been in a swimming pool change shed with clear whirlybirds on the roof, and they worked well to allow light into the shed (no ceiling space just a shed roof).  Can't comment about temperature because it was fairly cool days and I wasn't there for a range of days to compare how the temperature inside compared to outside temp.  If I was using them on a shed I'd use the clear ones.  Not on a house though. 
Peter

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## barney118

I put one in before I did a reroof (no sarking on a zincalume roof it made a huge difference inside the house, I then added ceiling batts (before they were free) and it was even better. I note I have vents (holes) under my eaves which helped draw air up to the whirly extracting the hot air.
On my reroof, I installed builders blanket (anticon) and put in 2 whirlies since I was happy with my first one, not looking back.

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