Has anyone installed a garage attic fan?

[commando1]

I'm telling ya, a cupola designed correctly will outflow an exhaust fan.
But I live in Fumbuck County in central Florida. WTF do I know....

 

[Stormer]

I'm telling ya, a cupola designed correctly will outflow an exhaust fan.
But I live in Fumbuck County in central Florida. WTF do I know....

That used to be true before the invention of the external baffle. Cupolas rely 100% on thermal bouyancy (warm air rises) where as a ridge vent actually creates a draw due to the Bernoulli principle.

 

[commando1]

Direct from the roofer man. I can't argue with you because you used the words "bernoulli principle". LOL. Yah, My learnin maybe woefully dated. ;-)
Cupolas are pretty, though.

So.... the volume of air moved is actually greater because of the higher velocity even though the area is smaller?

I'm going on the basis of a 1" gap along 30' of ridge X 2 edges is less than a 36" X 36" cupola ( basically a hole in the roof).
720 sq. in. vs. 1,296 sq. in. The flow is twice as fast?

 

[Stormer]

Air moving over any surface creates negative pressure which equals lift. If you intentionally direct the air up & over the vent from the windward side, it creates a strong negative pressure draw on the side away from the wind. When there's no wind then you're back to thermal bouyancy.

 

[commando1]

Got it. Thanks.
When there is a breeze, you're also sucking the air out in addition to thermal bouyancy.
Still air = thermal buoyancy only.
And ridge vents are better than cupolas when there's a breeze.
When there is no breeze, cupulas have the advantage because the total sq. footage of vent area is greater.
How am I doing?

 

[Stormer]

Good job, Stan. Gold star.