Bath vent fan exhaust placement – under gable overhang or thru shallow pitched roof
Am seeking advice on vent fan exhaust placement for a second story bathroom in my 1950 Cape Cod (zone 4-A).
Based on Martin’s bath fan article (link below), I prefer a gable wall termination for many reasons. However, am concerned because a recent dormer expansion causes my roof to overhang the wall’s exterior slightly (~8-inch). The vent’s termination would be within a few inches of this overhang (see photo – please ignore the moldy/mildewy vinyl siding, unless you have ideas of what’s causing it!).
The roof presents another challenge in that it’s pitch on the dormer side is ~2/12. If I go this route, I plan on using something like this gooseneck vent cap and hope for minimal rain/snow infiltration:
For either route, I plan on using 4-in flex duct for the first 1-2 ft, then rigid galvanized pipe for the rest of the run. I plan on wrapping all pipes with 2-in thick rock wool and angling pipes downhill where possible.
My question is – should I go thru the gable end and acknowledge that I’ll likely have dirt/mold/mildew above and around the vent termination, or go thru the roof and accept that water may leak down the vent pipe?
Many thanks in advance!
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