Wirlybirds

[Tonyz]

these are not of the female extraction with 2 much drink under their ....
We recently had a garage style extension biult that includes 3 bedrooms and covered entertaining area. It has recomended 'R' rating insulation in ceiling and walls but still get Bl.... hot on days like today 39* so whats your views of these exterior 'whirlybird'
things on your roof. Do they work, are they worth it.
ta Tony

[Barry_White]

They do help the only thing is you have to have at least a breeze for them to spin and to work. If you have a lot of glass you probaly need external awnings because the room will heat up through the glass and then your insulation is working against you by trapping in the heat.

Also if your walls aren't insulated you will gain nearly as much heat through the walls as through the roof.

Regards


Bazza

[soundman]

Whirly birds are a great sale item & they can work,
but
the chaep ones eventualy sease or go wonky or noisy.(they are mostly cheap ones.
you have to do a penetration in your roof (that doesn't leak)

they rely on rotation to keep the water out (see point 1 above) take a look at one from below once installed & youll wonder why water doesn't come floding in.

almost as much hot air comes out of a hole as out of a whirly bird.

So youve got the hot air comming out, where does the cool air come in?

I don't like the things in domestic applications.

however some roof cavity ventilation will reduce cieling tempritures a lot.

got gables? put a vent in it.

otherwise find some conventional way of getting a wheather proof & vermin proof hole in your roof and some eave vents to let the air in.
but first check if its cieling heat thats the problem.
get a step ladder and get up near the cieling.
Is it much warmer up there?
put your hand on the cieling
Is the cieling warm or even hot?


I know that just kicking off 1 tile hear the ridge can reduce cieling cavity tempriture 5 deg in a matter if minuites.
I used to crawl in cielings for a living.

OH. what colour is your roof.
you can drop your ceiling temp heaps by painting your roof white or at least a pale colour.
If its dirty get it cleaned.

cheers be cool

[Fantapantz]

All the above.....Whirly birds, vents in the eaves and gables............and paint the roof...........Going to get around to painting 1/2 the roof at my place with insultec, the racked cieling half..............
http://www.insulpro.com.au
This stuff (insultec) is used widely by BHP, Dept of Defence etc etc etc............It comes in two versions..........The membrane version that they say will last 20 years and the paint version that will last 8-10 years....................For the area i wanted done the price difference was $400 vs $1800..........I'm going for the paint version..........I'll prob sell the place before the paint peels......

[stephenmeddings]

If the roof is tiled then don't bother. There is enough ventilation in the roof cavity because of the gaps around the tiles. Not sure about a tin roof.

Must have blinds on the outside of the windows. You must stop the heat getting in the window in the first place.

[journeyman Mick]

Whirley birds are limited in the difference they wil make to the temperatures underneath the ceiling. Whirley birds and gable vents and all other methods of removing hot air from the ceiling cavity do just that; remove hot air from the ceiling cavity. This is great for anybody that needs to work up there but does little to cool the house down. Cooling the ceiling cavity will reduce heat conduction but will do nothing for the radiated heat. The most cost effective method for reducing temperatures is sisalation (builders foil/sarking). From Lysaghts table "Comparison of thermal performance" from their Steel roofing and walling installation manual: Approx. thermal transmission in watts per M2
Plain Zincalume radiated 4, total 15. with foil, radiated 2, total 5. With 50mm fibreglass and foil,radiated 2, total 5.
Weathered copper (ie. plain copper that's weathered so it's no longer reflective) radiated 120, total 140. With foil, radiated 8, total 20. With 50mm fibreglass and foil, radiated 6, total 15. Foil is cheap, has no moving parts to wear out and will help prevent water damage (but it does make any leaks harder to find).

Mick

[seriph1]

aaaah yes..... the age old - my GOD its hot up here dilemma!




I remember it well when I built into the roofspace of my first home - great idea but boiling/freezing. First I tried sisalation - then came fibreglass, followed by blown-in fluff of some kind - the latter working ok. Then a Velux roof window to assist getting the nhot air OUTA THERE fast. then a pair of oscilating fans - no room for ceiling fans. Then I bit the bullet and installed an $450 window mount aircon unit, that "vented" into the rest of the roof space and eventually added an exhaust fan and ducting to the back-end of that unit....... after only 13 years I got the space "just so"



regarding whirlygigs ...... what the other's said - I reckon theyre not the answer, though I am sure theyre good for moving the hot air out of the roofspace.

success

Steve

[seriph1]

forgot to mention - I installed the aircon unit in the wall - no window....... and if I hadnt sold the house I wouldve added a wented gable window too


Steve

[CraigV]

just finally getting around to checking out some of the other areas in this forum. So much info to read and learn from.

I have a small 3br brick veneer house with tile roof in the SW of Sydney where the temps were getting into the high 30's.

Had been seeing the ad's for the whirly birds and thought i would take the plunge, invest the money and hope for the best. One of the best decisions i have made. I went for the top end of the 3 models on offer, supposed to extact up to 100% more hot air. Within days of having them installed the difference could be felt in the house, even to the point of the house feeling cool when you walk in apposed to being slaped in the face with a heat wave when you open the front door.

The only thing is that on a hot "still " day they don't do much at all. but in saying that, i have watched them turn in the slightest of breezers.

good luck with whatever disision you make, hope this has helped

Cheers CraigV

[bitingmidge]

If it's 39° outside, don't expect whirlybirds to drop the temperature below ambient in the shade!

El cheapo whirly birds as has already been implied, are not worth the beer cans they are stamped out of. A quick visit to a roof space in which they have been installed will usually show about a three metre diameter pile of dust, leaf and other stuff which have arrived via the whirling thingy, with air travelling in exactly the opposite direction to the way it is supposed!!

This is probably because the fans are very inefficient, and the cool air is being sucked down in a sort of temperature inversion thing at night - other theories would be welcome.

They always spin, even in no breeze due to the convection created by the exhausting roof gas, and therefore do serve some limited purpose.

In my view ; use HEAPS of eaves ventilation, ditto in gables (but make sure that you can close off the gables in cooler weather when you want to keep warm air trapped in there) - another disadvantage of whirly things.

Better still, re-roof in metal and insulate directly under the roof sheeting. Keep the radiated heat out of the roof space, but trap the warmth from within in winter.

Cheers,

P

[Tonyz]

My workshop is a single car garage with pitched roof. I found a bundle of 'batts' in the recycle area of the local dump grabbed them then.... shoot lined under the wood rafters with 10mm MDF, ripped the iron off, laid the 'batts', then iron back on. then fitted a wirly bird into the ceiling/roof had a small gap so then fitted a bathroom air extractor under the wirly bird. WOW WOW with just the wirly bird I noticed a cooler [slightly] temp. but after the fan on for awhile it was enjoyable in the shed when outside it was high 30s

[seriph1]

know what you are?


youre an ideas man






I am gonna stop procrastinating now and do the same - wifey will be so happy, to not hear me bitching about the "bloody heat" all the time

success

[zathras]

I've got a whirlybird and shoved an exhaust fan in the hole pretty soon after I installed it.

Certainly gets rid of the hot air just sitting in the roof space above the roller doors because it can't escape fairly quickly.

I recall when I cut the hole in the roof how much hot air came spewing out and I was then convinced that the wirlybird would have to help with the ambient temp in the shed.

[soundman]

Just after the recent storms up here, I was driving down the road & what should I see but the head off some poor sods whirly bird. Obviously threw a bearing due to the high rpm. The poor sods woof is probably full of water.:confused:

[Greg Hudson]

Having just installed R3.5 polyester batts in the ceiling of a 310 square meter holiday shack - I can attest to the fact that on a 40 deg day, it can be 60+ in the roof cavity (well that's what it felt like anyway)!!!

We have TEN whirlybirds installed, and just today I was up on the roof preparing to paint it silver (Galvanized roof - lots of rust - used 10 liters of rust converter). Sorry - I digress...

Up on the roof today I noticed a huge heat haze emanating from all the whirlybirds (and it was only 26 degrees !!) Do they work ?

YES YES YES !!!

Regards, Greg.