Roof Ventilation

[Ausfree]

Because of the extreme hot weather we have been having, I have been thinking about installing roof ventilation to remove the hot air build up in the roof.

I have looked at those whirly gig thingo's that depend on wind power to remove the hot air and two things worry me about them....

1) they look unpleasant and are very bulky.
2) If there is no wind they lose their efficiency.

I see Masters hardware have a Solar Powered one on sale!!

Product Search*|*Roof ventillation

Any body with experience have any thoughts on these.

I think the hotter it gets,the harder they work. However, are they noisy and are they effective?????

[superquag]

Don't know about the Solar powered ones, IMHO they need to be big, say dozens of watts to make any real differance...
Whichever way you go, it is vital to have plenty of vents etc for outside air to get INTO the roof void... to replace the super-hot stuff you're extracting.

Indeed, you can't have too much, except in winter when you want to be storing the heat...

Have a look at prevailing breezes and utilise the wind to blow IN as well as suck out.

If you have evaporative A/C, then you may use a manhole or room ceiling vents as your flow-thru. We have a 1m x 1m manhole.... works well.

[Andwoo]

As a plumber Iv'e installed a few of those and think they are pretty good. I think they spin not because of the wind but from the thermal movement of hot air rising.. so I wouldn't worry bout them not working on a still day. I've never hard them making any noise at all when installed correctly. I've also been told they are good in winter as they prevent moisture from building up. I intent on putting a few on my own roof, don't think I'd bother with solar powered vents though.. seems like a gimmick to me.

What type of roof do you have? is it tiles or tin? Tiles are pretty good for ventialion as there are lots of gaps between each tile. If you have tin I think you'll notice a fair difference by adding ventilation as a tin roof seals up quite well.

[Rimmer]

Andy, (Andwoo) is right on the money!

[Stuck]

Superquag's pretty much on the money. Those "whirlybirds" will work as long as you have an entrance for air at a lower point such as your eaves. I've fitted them to industrial buildings during construction and I know how far and fast hot air will travel to get out (welding fumes from inside are a dead giveaway) when you cut that first hole .

Cheers,
Anthony.

[mike_ie]

I used to earn my keep in SA crawling round in other peoples attic spaces running cables from one end of the house to the other - to say the difference between roofs with whirlygigs and those without is an understatement. On a summers day it was easily a difference of ten or more degrees, so I reckon they do work, and well.

I also fitted two of the standard whirligigs into the roof of my ex's parents shed - put them almost at the apex of the roof, a few feet in from each end. The temperature difference was definitely noticeable immediately after they were installed.

[land864]

Andwoo

What are you dwiving awound in

I'll keep an eye out for you in the land of Nuts and Berries ( As our inner city so called friends call Nillumbik )

[Ausfree]

As a plumber Iv'e installed a few of those and think they are pretty good. I think they spin not because of the wind but from the thermal movement of hot air rising.. so I wouldn't worry bout them not working on a still day. I've never hard them making any noise at all when installed correctly. I've also been told they are good in winter as they prevent moisture from building up. I intent on putting a few on my own roof, don't think I'd bother with solar powered vents though.. seems like a gimmick to me.

What type of roof do you have? is it tiles or tin? Tiles are pretty good for ventialion as there are lots of gaps between each tile. If you have tin I think you'll notice a fair difference by adding ventilation as a tin roof seals up quite well.

It's cement tile, mate. Thanks everybody for your input.!!

[Andwoo]

Yer mate same as me, I think they breath abit so you'll have plenty of cool air flowing in while the whirlybird does it's thing
.G'day land864! I'm usually in my mazda bt-50, looks the same as every other white ute! I often cruise around in willy my series 3 when i can.. if you see him about give us a toot

cheers, Andy

[101RRS]

Testing has shown that there is no difference in temps inside the house but roof temps are reduced - not sure why but that was the finding.

Having said that, I have two large ones on my roof and they also have a fan attached to the whirly turbine at the top - they work by creating a low pressure spot that suck the hot air out. Also they provide a hole in the roof for hot air to escape. Mine are dead quiet and I have never seen them stop - even on a what seems to be a completely still pre dawn morning.

Garry