Attic Venting Options

Old 07-19-12, 11:41 PM
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Attic Venting Options

Hello all, new here.

I'm researching my options for upgrading the attic ventilation on my 2004 built home. The attic includes the attached garage, so there is roughly 2000-2500 square feet of space that needs to be ventilated.

There are soffit vents spaced evenly under the roof eaves that provide the air intake, but there are currently only 2 static circular dome type vents near the peak of the roof. When I purchased this home (fairly recently), the inspector mentioned that I should look into adding an additional 2 vents.

I should have enough room to add 2 additional static dome vents, but this would require cutting additional holes in the roof.

I'm curious if it would be feasible to swap out the 2 current vents and replace them with powered fan vents of similar size. To me this seems like an overall better plan of action that would theoretically be more effective.

The only thing that concerns me is that I don't know how to equate "net free air" from static vents to CFM on a fan.

Basically, would 4 static vents = 2 powered vents? I'm currently looking at the Broan 355BK 1200 CFM Roof Mount Powered Attic Ventilator, so I'd have 2 running which would cover up to 3500 sq. ft based on the product description.

Another option: since the cost of cutting holes in the roof would be free (I'll be doing the labor), should I just keep the 2 static vents and add 2 powered ones?

For the past few weeks I've been reading everything I can about attic venting and I know that you really shouldn't over do it, and ultimately you want a balanced system that cycles out the heat and the stale air regularly.

On the last note, I'll also be adding rafter baffles which for some reason were not installed by the original builders of this house. I'm slowly finding the strangest omissions that just make me shake my head.
Old 07-20-12, 12:45 AM
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Hello and Welcome to the Fourm , As a new home owner myself a month ago, I can RELATE about that shakeing of the head... i would leave the two vents and add the other 2 powered ones , That way you could almost pick where to put them and it might be closer with less wireing.. also you might want to check out any solar powered vents that might be availible and try and get a tax break in the meantime ;-) have you thought about those vents that have the ball on top that spins in the wind ? My inspector also told me i should add some vents so ill be looking into a solar type or even wind type with that funky little ball on top :-)
Old 07-20-12, 04:12 AM
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Having holes punched in perfectly good non leaking roof just does not make sense. Motorized vents will fail due to heat and are questionable as far as their ability to remove the hottest air at the peak. They often draw in hot air from adjacent vents as well, so they aren't doing what they are supposed to do. Continuous ridge venting is passive, requires no power, and evacuates the air in the attic completely without having holes in the roof. I would consider this as a high priority option.

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