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Sealing Around a Metal Chimney

suect | Posted in General Questions on

I have a home in Texas that has a foamed attic.  I have had 2 HVAC companies stating light can be seen around my metal chimney pipe, which can allow humid air in.  I was advised to have a chimney company come out to seal it.  Two companies were contacted and they stated it was normal.

I have read an article on this site that advises using steel wool to fill the void. Another suggestion was cutting 2 pieces of sheet metal to form around the metal chimney pipe and sealing with a high temperature caulk.

Is there a correct approach to this type of insulated attic?

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Replies

  1. suect | | #1

    Attached are photos from the attic.

    Thank you.

    1. Expert Member
      MALCOLM TAYLOR | | #2

      Sue,

      I think the chimney guys are probably looking at it from the perspective of it being weather-proof. That's a lot like the installations I see on vented attics without foam.

      Your second choice is the best one. First cut back the OSB sheathing to leave the required clearance to the flue, then remove the foam from around the metal roof-boot. Bed the two parts of the ring in hight temp. caulking before screwing them into place, as well as caulking the ring to the chimney flue.

  2. suect | | #3

    Thanks for confirming. My thoughts were to cut 2 “c” shaped metal pieces to form a donut shape to around the flue, prefer if there maybe something out there I could purchase.

    Would there be a recommended high temp caulk?

    1. suect | | #5

      Thanks. Could you advise the steps to place? Thinking of method to seal boot after it is cut.

      1. Expert Member
        MALCOLM TAYLOR | | #6

        Sue,

        That roof boot can't be cut and sealed.

        Be very careful about buying anything from Tiny Wood Stoves. Much of what they sell is for projects like tiny home trailers that aren't subject to approvals, and doesn't meet building code standards.

        1. suect | | #7

          Thank you.
          Would a product similar to this work if also using a high temperature sealant? It appears as though there is a flange that allows the potential for screws.

          1. Expert Member
            MALCOLM TAYLOR | | #8

            Sue,

            Probably. Those collars are typically slipped over the pipe and then tightened. Opening it sufficiently to wrap around the flue might cause the flange to crimp. Might be worth trying to flex it in the store to see if it opens enough.

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