ICC section 802 uses the term “ventilators” when determing attic ventilation needs. Local BI says that ventilators refer to the box type vents that go on the roof. I think that the term refers to all types of vent including soffit and ridge. How do you read that section?
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My understanding has always been that the speced number of square inches of vent should be rougjhly equally divided between soffit and rooftop.
Pressurize the attic
I worked on an article with Joe Lstiburek on this very topic a couple of years ago.
Check out " A Crash Course in Roof Venting" here:
https://www.finehomebuilding.com/how-to/articles/a-crash-course-in-roof-venting.aspx
Here's in interesting point from the article:
"Building codes suggest balancing the intake and exhaust ventilation. The code, however, is wrong, and I'm working hard to get it changed. More ventilation at the eaves than at the ridge will slightly pressurize the attice. A depressurized attic can suck conditioned air out of the living space, and losing that conditioned air wastes money.
For best results, provide between 50% and 75% of the ventilation space at the eaves; a 60/40 split is a good sweet spot."
The article also has a formula for calculating the correct amount of net free-vent area (NFVA)
-Rob
Design Editor