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RM575 10-07-2012 07:49 PM

Eave vents, how much NFA per 2" hole?
Hello folks,
I'm trying to calculate how many holes to drill in the 2"x6" blocks of my eaves in a 11'x15' detached workshop that has a 4:12 hip roof. It will be insulated and drywalled.

I'm trying to balance the attic ventilation and will be using the 1/300 calculation instead of the 1/150.

It looks like the NFA (net free area) of the attic requires 40.32 sq inches for the exhaust and the same for the intake.

I'm looking at installing a static roof vent that provides 41 sq inches of NFA.

Then I plan to drill 2" intake vents at the eave blocks but need to know how many to drill.

If I've done the math correctly, a 2" hole is 3.14 sq inches in area, which would mean 13 2" holes for intake.

Can someone verify this? Is there a reduction in the area when screened with 1/4" wire mesh?

