On the back of my garage I have a flat roof/deck. I-joists are at 12″ O/C with cross purlin’s at 12″ O/C. I would like to know if 2- 1 1/4″ holes in each joist space is enough for air flow in the joist space. I don’t want to go to big of holes because the joist are only 9 1/2″ high and I need insulation covering the top plate.
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normal standard is one sq ft of venting in and out for ever 100-150 sq ft of floor space
I usually don't vent a flat roof. Soffit vents let the air in - how will it get out again?
Will you be heating this garage? heat and moisture is what drives the need for venting.
The pop-in vents like this are usually for retrofitting when that is the best you can manage, because they are too small to do much
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Thanks, the garage will be heated. It can only vent to one side of the deck space.
In that case, you really have no venting without cross air flow both in and out. You can put thoe in for show I guess, but I would be sure to seal the VB tight by placing plastic there to keep moisture out of the ceiling/roof assembly in the first place, since you can't vent it out.Be sure to tight caulk any penetrations
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