Browse Forums Building A New House Re: who has installed a whirlybird to their roof? 10Dec 09, 2008 2:48 pm Actually I don't think the science has been settled on this issue. Whirly birds apparently do work.
Read Whirlybirds do work: http://forums.envirotalk.com.au/Whirlybirds-Work-t7938.html Re: who has installed a whirlybird to their roof? 12Dec 09, 2008 3:51 pm BigKev Actually I don't think the science has been settled on this issue. Whirly birds apparently do work. Read Whirlybirds do work: http://forums.envirotalk.com.au/Whirlybirds-Work-t7938.html Yes but if your read the content of it you would realise that the main supporter of it has no valid argument: Briefly: - hot air rises so it is not as hot near the ceiling as it is near the roof - hot air actually doesn't contain a lot of energy to transmit through the ceiling - in Summer the heating comes not from the hot air in the roof space but comes from the hot roof radiating heat directly onto the ceiling - removing the hot air with a whirlybird doesn't actually deal with this problem - the best way to stop the roof radiating is to use reflective foil Lastly the best proof is actually in a real life experiment in a house where they put in solar powered whirlybirds. They discovered it only reduced cooling requirement by about 6%. Our usual wind-powered whirlys probably wouldn't even achieve that! I wouldn't waste my money. Anyway foil is cheap - $2/m2 You could prove it to yourself. Place a thermometer on both sides of a ceiling. The air temperatures are nowhere near the same. Very little heat energy travels through. You could do a little experiment to show how well foil works. Get two cardboard boxes and line one with foil. Take them into direct sunlight for an house and compare the temperatures inside. Re: who has installed a whirlybird to their roof? 13Dec 09, 2008 3:55 pm BigKev Actually I don't think the science has been settled on this issue. Whirly birds apparently do work. Read Whirlybirds do work: http://forums.envirotalk.com.au/Whirlybirds-Work-t7938.html BOY, I started to read the link above but I don't have a spare 3 hours to go through the whole thing, because they are relatively cheap so if they make a very small difference I think it may be worth it when you consider the whole cost of the project. Re: who has installed a whirlybird to their roof? 14Dec 09, 2008 4:03 pm vid BigKev Actually I don't think the science has been settled on this issue. Whirly birds apparently do work. Read Whirlybirds do work: http://forums.envirotalk.com.au/Whirlybirds-Work-t7938.html BOY, I started to read the link above but I don't have a spare 3 hours to go through the whole thing, because they are relatively cheap so if they make a very small difference I think it may be worth it when you consider the whole cost of the project. Exactly! Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: who has installed a whirlybird to their roof? 15Dec 09, 2008 4:08 pm vid BigKev Actually I don't think the science has been settled on this issue. Whirly birds apparently do work. Read Whirlybirds do work: http://forums.envirotalk.com.au/Whirlybirds-Work-t7938.html BOY, I started to read the link above but I don't have a spare 3 hours to go through the whole thing, because they are relatively cheap so if they make a very small difference I think it may be worth it when you consider the whole cost of the project. If you put foil in you will make a real difference. Actually about 20% reduction in cooling requirements. And it will be good for your air con system and as a condensation drainage plane. Whirly's in a humid environment may actually be detrimental to moisture control by bringing in unwanted moist air into the roof space and rotting your timbers or rusting your fixings. Re: who has installed a whirlybird to their roof? 16Dec 09, 2008 4:15 pm Dymonite69
I have read both sides of the argument and neither is 100% correct. Unfortunately, you are too emotionally invested in the negative argument to be considered an unbiased source. All that I did was put up a counter argument. There are way too many factors to be considered before dismissing anything out of hand. Location of house and climate of area, what type of insulation will be in the roof, what the roof is constructed of (tiles or colourbond), etc. To dismiss something out of hand without taking into consideration all factors is very shortsighted. Re: who has installed a whirlybird to their roof? 17Dec 09, 2008 4:52 pm BigKev Dymonite69 I have read both sides of the argument and neither is 100% correct. All that I did was put up a counter argument. There are way too many factors to be considered before dismissing anything out of hand. I can always change my mind with the right evidence! I would be interested to know your rationale for the value of whirlybirds. My position comes from two studies where the effect of whirlybirds were specifically examined and directly measured with temperature sensors (e.g. not hearsay or opinion or anecdote) http://www.build.qld.gov.au/research/li ... Report.pdf from p.26 "Ventilation of roof space There is 2.4m2 of ventilated roof space to assist in reducing the temperature in this space. The large openings create air mass movement, which assists in removing heated air and replacing it with outside ambient air. Its impact on the temperatures in the living areas is minimal in Research House...." This second study looked at powered fans and the effect on both roof space temperature and reduction in cooling load. http://www.fsec.ucf.edu/en/publications ... gp-171-00/ Are you aware of any studies demonstrating benefit? Re: who has installed a whirlybird to their roof? 18Dec 09, 2008 6:38 pm I hope this isn't too far off topic, but I'm intrigued by the recommendations for reflective insulation.
A couple of factors that often seem to be ignored at the installation phase are: 1. The manufacturers state the sarking needs to be draped (ie hang down between the purlins) not pulled tight. I'm sure most of the time it is installed so that it is virtually touching the roofing material over the whole surface. Maybe the corrugations are the only way it ends up being effective. 2. The reflective surface is only on one side of the sarking. So how can it reflect radient heat from outside if it's installed the usual way with the reflective surface downwards? Hopefully someone can shed some light on this. Cheers zeke BTW, I'm fascinated by the explanation of why ventilating the roofspace doesn't help to cool the house. Drawing on my high-school physics from decades ago, I must admit it makes a lot of sense in spite of being somewhat counter-intuitive. Re: who has installed a whirlybird to their roof? 19Dec 09, 2008 7:00 pm We have 2 whirley birds on a colour bond roof, steel frame home so moisture rotting the timber frame isn't an issue, anyway where we live it is hot and dry and windy, small outlay, seemed a good idea. Re: who has installed a whirlybird to their roof? 20Dec 09, 2008 10:27 pm Zeek correct - Sisalation does need to be draped and correct many times it is not installed with a sufficient gap - therby reducing it's performance.
Dynamite - Theory from a couple of sources is all well and good - but be careful of the web not being all true and correct :d So as a test of your theories - Grab a section of silver sisalation (I've got new 60 metre roll if you need some) and on a hot day stretch it out over a metre square cardboard box and then measure the temperature inside (shade the sides of the box) Do the same with another box at the same time with sheet of tin and some R3 or 4 insulation and tell which one works best. Then you'll have a bit more measured data of your own - I'd be interested in your results - because my experience and data is not as you propose in your previous threads. As for whirlybirds - I was in the old Perth gaol last weekend and the 1800's gaol has an excellent whirlybird that is a 3 foot diameter fan that vents the entire room through the roof. On a 27 degree day it was naturally spinning with the convected air that was moving through it. The trick with roof ventilation, is to ensure that you are using it to draw air into the house, and venting out through the roof space ensures you create good ventilation, as well as remove the heat from the roofspace. But it's better if the entire house is designed around it - not just an add on. One option for existing houses or non ideal airflow designs is to use a system like the cardiffair. http://www.cardiffair.com.au/index.php?module=pagesetter&func=viewpub&tid=2&pid=1 And these articles explain how whirlybirds and vents or windows can make the house nicer to live in - in summer. http://www.energyarchitecture.com.au/media/21-ada-st-documentary/ http://www.beyondtoday.com.au/pageflip/design_guidelines/design_guidelines.pdf Steve This is not installed to the manufacturers installation specification and hence is not fit for purpose, voids warranty and possibly not meet code. I’m not sure on the… 3 2690 6 2332 |