If a "2.5" car (24x24ft) garage has one roof vent near the top, is there any use in adding an extra roof rent? The garage is unfinished/uninsulated, and there is no obstruction of air between the roof and bottom of the garage. Also consider a Northern Ohio climate (hot+humid summers, freezing+snow winters).

I'm thinking a 2nd vent could help with flow/cross-breeze, but it may also just add to the probability of leaking somewhere down the road.

If a 2nd vent should be added, where? If there were two vent near the top, I feel like that wouldn't do as much as one near the top and the other near the bottom of the roof. But I also think it would look ugly to have a vent that low.

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    Is the garage excessively hot (for a non insulated structure? ) I would think a solar powered vent would be a better solution, when the sun is out and hot the vent pulls the heat out, at night it’s not hot and unless a really full moon the fan won’t run :)
    – Ed Beal
    Mar 19, 2020 at 23:33
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    If you want "flow from the bottom" put in soffit vents, which are practically invisible and specifically designed to achieve that. Or just expect air leakage from the garage itself to supply adequate air, which is probably true unless your garage doors are abnormally tightly sealed for an uninsulated garage. Hard to know if more vents are needed since we don't know what problem, if any, you are trying to solve, nor the size of the vent you already have.
    – Ecnerwal
    Mar 20, 2020 at 2:41

1 Answer 1


You do not need roof vents for non-insulated open roof garages.

FYI: For attics, the typical ratio is 1:150, so for every 150 sf of space then install 1 sf of venting. You have 576 sf so if you were to need them, you would need a minimum of 5.8 sf total.

  • Your traditional builder will put one (or a cupola vent if a very traditional builder) to help mitigate exhaust fume buildup / make it harder to commit suicide (inadvertently or otherwise) by running the car in the garage.
    – Ecnerwal
    Mar 21, 2020 at 2:08

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