Thread: roof ventilators ( house )

the ventilators go up near the ridge line about equidistant from the ends and each other.

but the vents are going to be a bit of a conspiracy theory....

do you want them in the house sucking the air out of it and drawing fresh but hotter air into the house OR do you want to put them in the eves outside so that the air can circulate in the roof space leaving the air in the house untouched save for what gets drawn in via the kitchen extractor and toilet/bathroom roof vents?

I like the latter idea ESP when it comes to heating in winter.

What Dave said. Bung the vents into the eaves.

Fans flash under the ridge capping. Vent the roof space only.

Do they work though.

The ones bunnings sell just have the whirly thing - I was told the logic is that the wind turns the whirly bit that creates a vacuum that in turns sucks out the hot air - but I would have thought the wind entering the whirly bit would have filled any vaccum and the hot air would stay put.

I have seen some that have a fan connected to the whirly bit so that the wind is driving the fan which extracts the hot air - Bunning models cost about $80 but the ones with the fans are closer to $200.

I am interested in this because my house is a hot house - normally getting hotter than the outside air in summer - is a high house, lots of glass and faces west.

Garry

Gazza. Air in (eaves) = Air out (vent).

The hot air flowing through also spins the vanes as does a very light breeze. In fact, even when I cannot see the leaves moving, the vent is spinning away.
Seems to work for me but I really do need more inlet air (problem ex- motor garage/ now garden room roof.)


http://www.laserlite.com.au/resident...pinawayMK2.asp




http://www.laserlite.com.au/commerci...iteIndvent.asp

the simple ones work, I put 2 in the house in townsville and providing I remembered to keep the downstairs part closed up it dropped the house tmep 3 degrees And I could work in the main roofspace during the day if i really needed to.

they work paritally on centrifical force, partly on vortex dynamics and partly on hot air rising.

on a day with dead still air you will see new ones (or well maintained old ones) slowly turning from the hot air venting out of them they are essentially at this point just an opening in the roof.

when they are spinning from external wind the downwind side of them develops a vortex (like the back of a landie on a dusty road) that sucks the air out of the whirly gig (anyone who points out the whole no such thing as sucking gets a free set of curses and an addition to my "things I hate" list)

and when they are spinning the air inside them is centrifuged towards the outside and then out the vent slots.

Heres something fun....

If you look at one of the cheap ones(call it $80 as previosly mentioned) and then one of the expensive ones($200) you will notice that aside from the addition of a metal or plastic fan in the middle of the shaft that supports the whirly gig spinnery bit they are identical... and all that holds it together is a metal shaft 2 support bearings a couple of washers and about a 10mm nut...

If you goto the tip/junkyard/recyc shop you will find lots of extractor fans (the ones that go in the ceiling for your bathroom/toilet/kitchen) that have a plastic fan on them.. Find one with the same shaft diameter as your whirly gig, pay the man $5 for a burnt out one then go home and dissasemble both the whirly gig and the extrator fan. Drill the mounting spigot for the fan all the way through with the same size drill as your whirly gig shaft then assemble the fan onto the whirly gig (pay attention to fan orientation here) secure in place with some 2 part epoxy, the little mounting grub screw or some loctite bearing lock.

you now have an $85 whirleygig that is more or less exactly the same as a $200 whirly gig.

If you put a pully on in place of the little nut at the bottom (use a thrust washer and a grubscrew located pully) you can attach a small 12v stepper motor with a pair of blocking diodes and a capacitor that will happily charge a 6v gel cell battery that is more than capable of running LED lights in the ceiling as emergancy lighting for when the power goes out (or when you blow the bulb in your work light while your up there)

Aside from the fiddly stuff just just talked about, I am on my second set of ventilators, the only difference was i wanted to maximise the eave vents so I have 6 coming from the back through a skillion roof to a pitched roof and out.
just had the roof replaced , corrugated zincalume, on top of sisalation, to date the house is 10 deg cooler than before,a lot easier on the A/c's
i only put the new spinners in last week.
the easiest way to test the draw, from the eave vents is to go to your manhole on a warm day and open it up, you should get a sudden instant rush of air straight past you and into the roof.

I wouldn;t use the in room ventilators, because as BK said, what goes through them must come from somewhere and outside air is the obvious place, trying to get rid of heated air and replacing it with heated air defeats the reason for having them.

the electric, thermostat controlled ones, with the fan, I think they are called the 'thinking cap' use electricity and have to be wired, the others spin with or without wind.


john

I'm thinking about a couple of them as well, after yesterday then todays heat our house is like a sauna and we only just got our 7 mnth old to sleep after first trying at about 7.30. Also looking into evaporative cooling as the little box aircon unit does squat. Our eaves are fully enclosed so maybe some vents spaced around the house would also help.

Thanks for the replies guys, much appreciated ... I knew ther'ed be a wealth of knowledge on this.... us LR owners like "alternative" solutions to things ....
a lot to read through there I'll have to print it out and go through it all.

couple more questions leading from your comments :

1. these are the type of extractors I have bought http://www.edmonds.com.au/html/produ...ator_250mm.htm
the instructions say if you have a non-sarked tile roof there is no need to put the vents in the eaves because enough air comes through the gaps in the tiles. Is that true ?

2. we have downstairs a double brick basement that is hafl undergound and stays really cool in the summer ( in fact we sleep down there when it gets really hot. ). My theory in putting in the ceiling vents was to perhaps draw some of the cooler air from downstairs in to the main living area upstairs. Would that work ?

3. Our upstairs is brick veneer. The inside plaster has the wall vents up near the ceiling. Now I heard that those vents actually let hot air in from the space between the bricks and the plaster, and you can now legally block them up. Is that true ?