Why whirlybirds are not needed on metal roofs

[@urbsimp5273]

As a building designer that has to deal with this B/S everyday this is a simple solution that should be investigated further. We need to prove compliance through an alternative solution to the NCC showing that enough air volume moves through the roof to meet their current requirements and that the condensation is NOT going to create another issue. It’s becoming insane the amount of compliance requirements now needed to fix problems that have been legislatively created. Solutions like this stop adding more and more money to the builds, like adding whirlybirds and eave vents, hopefully allowing us to start controlling the outrageous cost of building.

[@kussemeinkont]

On a hot day the more roof ventilation the better. I live in SA and we don't suffer from condensation, the heat build up in the roof space is the problem.

[@skullandcrossbones65]

G'day, How would this change impact Bush fire ratings? What would you have to add to prevent embers entering the roof cavity?

[@rnb250]

In future couldn’t corrugated iron be manufactured with a thin backing that would stop condensation, allow ventilation and be mess proof to allow for cowboys not following the rules?

[@roofingportal]

They tried this many decades ago and got 'burnt' Moisture managed to get between the backing and the metal and started to rust the roof sheeting from the underside. Lysaght lost a lot of money on this - I guess...

[@rnb250]

@ time to try again?

[@wotmate]

The building blanket doesn't stop condensation from forming, and the reason why it's supposed to go into the gutter is so condensation can drip into the gutter. By cutting the blanket short like that, it just means that condensation drips into the roof cavity.

[@pauloconnor7951]

Drip into the eve cavity. Yeah but it's a trade-off. I think I'd prefer under eve vents plus whirlybirds. 👍

[@gertsy2000]

@@pauloconnor7951 Agree.

[@frankryan2505]

Yeah..cannot believe that this guy is suggesting to cut the blanket short of the gutter,goes against every recommended installation guide i've ever seen.. Try run that through a commercial certifier and you will find yourself ripping up deck to patch your mistakes... Fascia vent with a gutter flashing (detail similar to B/G) and you are sweet for eveless ventilation..only going to add a few hundred bucks to the job and its done correctly! The literature on this is so bloody straightforward i cannot believe someone would take their time to try find a loophole around it..

[@sydneyshinshi]

Anticon does what it says it does. Its stops condensation and the foil is to catch any leaks. I think it is a good idea what he is suggesting

[@donsheehan5144]

If the roof isn't steep enough, and I have never done the maths, condensation between the blanket and the ton will sit in the sag of the blanket. There are alot of houses with part flattish roofs.

[@adamsmith-bq8ku]

Spend your money on higher quality ceiling insulation instead of roof spinners.

[@ryanclarke2161]

whirly birds are stupid and you can just use vents with no moving parts. i am sick to death of people saying they are wind powered vents.........god i just hate them and the morons that think they work.

[@andymartinez767]

Whirlybirds are wind powered and do work

[@trythis2821]

@@andymartinez767 Whirlybirds spin and are another thing to wear out (make noise and possibly leak) that don't serve any useful purpose. Unless you are spending time in the ceiling don't bother.