Passive attic ventilation without soffits, does it work?


Old 09-23-04, 09:53 AM
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Passive attic ventilation without soffits, does it work?

I live in Portland and have 150 degree unventilated attic temperatures in the summer and humidity that needs to be flushed out all year round. My old house has no soffits under the eaves for me to place soffit ventilation to accompany a ridge cap along the top.

The roof also has about four years of life remaining and there are no gable vents. Can I skip the soffit vents in lieu of placing ~6 evenly spaced mushroom vents as low on the roof as I can get them (3 each side)? Then I would likely place ~4 near the ridge cap if that would be effective. I am hesitant because my contractor told me mushroom vents aren't worth a crap and I don't look forward to an attractive row of vents visible from the front of the house.

Sticking a powered fan up high is great except there is no current place for it to suck air from, leaving it to pull warm air form inside the house over winter. Cutting gable vents through three levels of siding and reinforcing the framing to code is a bit beyond my skill level.

Any advice for ensuring air is moving through this stagnant space?
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Old 09-23-04, 02:02 PM
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I misread this the first time, it's not that you don't have soffit vents, you don't have soffits, ie, no overhang. We've had a couple of houses with the same situation, you can get what I call "birdhole" vents, they're round, 2"-3" diameter IIRC. You use a hold saw and saw into the FASCIA instead of the soffit, (this assumes you have no gutters to block them). Once they've been painted you don't even notice them.

Make sure you add the ridge and soffit (or fascia) vents in the correct proportion. IIRC it's 2:1 ridge:soffit. And dont' add gable vents, they'll reduce the efficiency of the ridge/soffit system.

Old 09-23-04, 03:26 PM
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Thanks for the input.

I have seen those birdhole vents and they are a possibility. I just don't know if they are going to be worth the effort because of the huge number I would have to hole drill through my 4*6 support beam that sits at the uppermost point on my exterior walls. I think to adequately ventilate my 800ft sq space I would have to drill ~20-30 hole-saw holes through this beam from which these eaves extend. That is fine if that is the best solution and I am up for it, it will just take a lifetime with a 3" wholesaw.

When I said I have no soffits, perhaps I misspoke. I have eaves that extend three feet and they consist of 2*4 supports topped with a row of boards, then shingles. The eaves either are tacked onto the 4*6 support beam or extend from the attic trusses out but there is no soffit structure covering them and connecting into the attic.
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