Roof Vent Question.

Teetorbilt

This is a flat roof, 2X6 rafters, 24" OC, 24 ft. long. The space over the ceiling is completely filled with fiberglass batt. The soffit projects 18" on 3 sides. There are 4, 4" circular vents across the 24 ft. span. WHY?

Common sense tells me that the space between each rafter/insulation/fascia constitutes it's own space and should be vented or not. Why vent only 4 of these spaces? Am I missing something? What's the right way? BTW, I'm just replacing some rotted soffit and fascia, the roof is pretty new.

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You can't solve you're problems with the same level of thinking that created the problems.

Albert Einstein

Forry

Those vents aren't doing anything. Not sure how I would go about venting that kind of situation, but it seems like even a flat roof needs some help venting vapor.

Teetorbilt

I have no access to or knowledge of how or if it ties into the roof trusses. The opposite side of the roof is vented in the same manner with no ridge or gable end vents.

__________________
You can't solve you're problems with the same level of thinking that created the problems.

Albert Einstein

Ed the Roofer

The NFVA of each of those mini-circular vents is almost non-existent, like around 3-4 sq inches each.

Every rafter bay that is a seperate contained air chamber, in theory, shoud be vented. I just got involved in a very similar thread on insulation a flat roof in the building science section on the JLC board 2-3 days ago.

We even discussed the alternative methods for proper exhaust of the contaied air spaces as well.

Some good suggestions eventually wound up being discussed. Check it out, but it goes about 60 + posts long, but the last 20 or so would be relevant to your inquiry.

Ed