I have a 100' ranch house with a low-pitch roof that has 40" overhangs, exposed 2x10 rafters and openings between the rafters that are plugged to prevent all air intake. Two years ago, the wood roof was removed and replaced with 5/8 inch sheathing, 30 lb felt and a 50-yr warranty shingle that uses ridge venting. We have exhaust venting, but no intake venting. We have noticed some staining on the inside of our great room where the roof meets the side wall. We think this may be caused by condensation and that we need to add intake ventilation to the now plugged soffit areas, but it could be due to Kansas driving rain getting in through our ridge venting.

Has anyone experienced this problem and know a solution? I do think we need to improve our intake ventilation at the soffit location so we get an even flow across our 100' length. What
vent fixture can we use for this? It must be good enough to prevent leaks from driving rain and to prevent insect entry? I have the tools and skill to install these vents; and realize that I will also have to install styro venting buffers on the inside of each vent. Help!

Forty-inch overhangs with no soffit venting is a formula for ice dam disaster, and that could be what your stains are coming from. Tracing leaks is always difficult, but I doubt that the ridge vents would produce staining at the exterior walls.

The simplest way to add venting in existing soffits is by installing circular screened louvers such as Minivents. All you need is a hole saw. The number and size of the vents per joist bay should be calculated. You should have 1 square foot of free area for each 150 square feet of attic floor area, and half of that should be in the soffits.

Remember that free area of any louver is usually on the order of 50-75% of the gross area. Consult manufacturer's literature for exact free areas.

Richard,

Thanks for providing information on materials needed, related calculations and your experienced thoughts on the cause of my problem. Now I can get out my calculator and determine what is needed to git-r-dun.

I live in Kansas now, but am a native Pennsylvanian; Lewistown, just West of Harrisburg. See where you live to the East, not too far from the OCC boys in NY.

Thanks again for the quick and helpful info.

Dick