# Attic Ventilation Inadequate?



## redpoint5 (9 mo ago)

I live in the PNW and bought a house constructed in 2003 about 3 years ago. Although this didn't come up in inspection, just looking at the soffits, I felt that the sparsely spaced 2" round intake vents were inadequate for the size of the roof. I mentioned that I wanted the intake ventilation looked at as a contingency for sale, and the owners added more exhaust vents instead. I bought the house anyhow because we needed to move, and intake ventilation should be easy for me to add myself (and I don't want any more incompetent work being performed).

I'm no expert, but the internet says I need 1/150 ventilation to attic area.

Using Google Maps, I estimate I've got 3,300 sq/ft of roof.
I counted 21x 50 sq/in exhaust vents (I need to get on the roof and verify those square vents are indeed 50 sq/in) = 1,050 sq/in
I counted 72x 2" round intake vents (1.5 sq/in effective ventilation) = 108 sq/in

If my counting, math, and understanding is correct, my intake is 10x undersized for the amount of exhaust I've got. If I match my exhaust capacity by adding intake ventilation, I'll be at 2,200 sq/in total. Still about 1,000 sq/in less than ideal, but a massive improvement over what I've got.

Am I understanding all this correctly? I'm hesitant to add 10x more of those dinky 2" round soffit vents because that would be 720 more holes to cut and vents to install.


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## roofermann (Jul 7, 2012)

They make those round intake vents up to 4in diameter, take far fewer of them.


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## redpoint5 (9 mo ago)

I'm assuming my math isn't wildly wrong based on what I've described?

Kinda hard to imagine the house was built with 1/10th the proper amount of intake ventilation, and that it then passed inspection.


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## roofermann (Jul 7, 2012)

Adequate intake venting might not have been a thing on the bldg. inspectors checklist back in '03, or it was something that slipped by him or her. My understanding is that having the intake and exhaust balanced is more important than the amount.


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## redpoint5 (9 mo ago)

Attic temp is hitting 115 when outdoor temp is 75 degrees. I've read that temps above 130 are unacceptable. We'll see how attic temps do this weekend when we hit 96 F.


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