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Old 06-10-2011, 08:05 PM   #1
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Balancing attic ventilation


Hello,
I have a 1.5 story home with 76 linear feet of ridge vent. I don't know if it's the rolled type ridge vent or not but during an energy audit about 6 months the guy told me it was installed correctly. Based on what Ed said in another post that should give me roughly 1368 sq inches of venting (18 sq inches per linear foot). I also have about 85 linear feet of continuous soffit venting. I have attached a picture of it to help. I am not sure of specs on this soffit vent. It is 12" wide, actually only 11" that can pass air.

My problem is on a 95 degree day, like yesterday, the attic reads 130 degrees. It almost broke the thermometer testing it. And when I am up there I can barely see any noticable airflow. Cobwebs hanging from the underside of the roof hardly move in the channels rising from the soffit vents.

I educated myself on attic sealing and insulation and have done all that was recommended during the energy audit. The soffit vents seem clear and the insulation is not blocking airflow up to the ridge vent. I know powered attic fans aren't recommended with ridge vents.

So, basically I am not sure if my intake is anywhere close to what it needs to be and I am not sure how to calculate it. If it is insufficient then how would I fix it?

Thanks for your input.

Bob
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Old 06-10-2011, 11:24 PM   #2
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Balancing attic ventilation


Welcome to the forum!

If your soffits are 2' deep from house to fascia, you are probably fine, giving you 4.68 NFVA per foot times two = 9.36NFVA.

http://files.buildsite.com/dbderived...rived92755.pdf

That, plus the other side balance to the ridge vent exhaust NFVA. Personally, I would trust a continuous soffit vent located near the fascia board for better intake and no house pressure: pp.616: http://books.google.com/books?id=Z8a...0vents&f=false

If only 11", you are getting about 4 NFVA, or 1/2 as much as you need.......

Gary

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Old 06-11-2011, 06:07 PM   #3
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Balancing attic ventilation


Gary,

Thanks for the info. I have the 11" soffit panels which means I need to double it somehow.

Do you have any ideas on how I might correct it, maybe replace the soffit panels with something else??

Bob
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Old 06-11-2011, 11:18 PM   #4
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Balancing attic ventilation


Just pull down the vinyl, add backing framing and continuous vent strips, solid vinyl or cement board.
http://www.airvent.com/homeowner/pro...it-specs.shtml

Gary
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