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HeyBub[_3_]

wrote:
On Apr 8, 9:21 pm, "HeyBub" wrote:
DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide
soffits, like 12" or more.

On houses with narrow soffits, box vents are recommended.

Any truth to this?

Basic rule: You can't have too much soffit vents.

At a minimum, you should have one sq ft of soffit vent for each 150
sq ft of floor space. This is one sq ft of unobstructed venting.
Some screening material consumes as much as 2/3rds of the space.
Refigure accordingly.

If you have a 1500 sq ft house, you need 100 sq ft of soffits,
minimum. Assuming the screening material is hardware cloth or
similar that consumes less than 20% of the opening, you should plan
on 120 sq ft of soffit venting. Further, assuming small, six inch
soffits on a 50 x 30' house, you have 160 feet of perimeter. That
means only 80 sq ft, maximum, for available soffit vents.

Obviously this is woefully insufficient for the appropriate amount of
passive ventilation.

There is an error in your math. Assuming you need one sq ft of
venting per 100 sq ft of floor space, then a 1500
sq ft house needs 15 sq ft of venting, not 150. You're
off by a factor of 10. Following through with the
math, you'd then want 12 sq ft actual. If you did 2"
wide vents, you get .16 sq ft per linear foot. Which
in turn means those 2" wide vents down just the
long sides of the house would give you 16 sq ft total,
meeting the min reqt.

Also, technically, it's not floor space that
counts, but the attic area that is being vented. Some
houses don't have just one open continous attic area.

Yep, you're right. My bad.

I appreciate the correction and congratulate you for preventing someone from
making a grievous error based on my calculations.

Still, my answer was closer to being right than someone who announces
"purple" as the solution.