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Community and Q&A

Insulating a Bathroom Exhaust Pipe

mgensler | Posted in General Questions on

We gave our contractor specifications found on this site for our new bathroom exhaust fan and piping. They ran the 6″ galvanized pipe tight against the ceiling in the attic and forgot to cover the pipe in vinyl-faced fiberglass insulation. They said they would take care of it but then their spray foam person covered both ends of the pipe in a large amount of foam. This locked the pipe in place and now it won’t come apart. They are suggesting they cover the rest of the pipe with spray foam. We would still have bare pipe touching the top of the ceiling. We are in climate zone 4a. Is this acceptable?

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  1. tvrgeek | | #1

    I gather the concern is that if there was condensation, maybe as the pipe turns to exit the roof, it could run down and leak through the ceiling? If it is down exit through the soffit, then no way for condensation to run back, I would just insulate the top of it.
    Thinking about a perfect world. Maybe I woudl use a PCV pile and a gentle slope so any condensation woudl run down to the soffit damper and out. Insulation above it so pipe on the protected side. Maybe crazy. Mine are all wrong so thinking about best solution. ( flex stuffed in soffit, no proper grill, damper etc. )

  2. mgensler | | #2

    Yes, condensation is the concern. The pipe runs across the ceiling and then angles up to exit through the roof. I can't really change any of that without ripping out the pipe. Thus the idea from the insulation contractor to just cover the exposed pipe with spray foam.

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