I was in the garage attic and noticed I have two dark areas on the underside of my house roof. I pulled some insulation away and see that I have condensation on my plumbing vent. The area is damp and I am leaving the insulation out of the area to help air flow. How can I fix this to prevent condensation from occuring over both bathrooms? I was thinking of making a small soffit and spray foam it to create a better insulated area.
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Not there so only comment after viewing your pics, but….
Looks here from Ohio that you might be thinking bogus installation of the vent boot. Sealing the pipe to it might just goop things up and still have a slow leak.
Bad seal to the roof deck and you cover it up, wet and deterioration of the sheeting continues.
Can you take a photo that shows where the plumbing vent is, and where it exits the attic?
I think Calvin has the right answer, bad flashing or boot installation. Try gooping up the outside first.
Condensation is the result of relatively warm, relatively moist air encountering a relatively cold surface- think of a cold beer can in August in New Orleans. A plumbing vent would usually be a relatively warm surface, transmitting heat from warmish water and a warm room into relatively cold, dry attic. This argues in favor of the leak related problem suggested by calvin & 1095mike.
Remember that goop is the last refuge of an unskilled roofer.
Reminds me of a saying …..
Caulk and paint
Make for what a carpenter ain’t.
Which might be a bit off…
Is there a bathroom fan (or two) that are not properly vented outside the attic?