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Insulating around chimney in attic -- need advice. Pictures included.

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by PopulistWoodBurner, Oct 31, 2010.

  1. PopulistWoodBurner

    PopulistWoodBurner Member

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    My stove was just installed and I had them run a new chimney pipe for it. The installer said I could stuff some fiberglass insulation down inside the insulation guard, as you can see in the picture. He reasoned that the insulated chimney pipe itself was insulated with fiberglass, so this was no different.

    After he left, I got to wondering. What would the point of the insulation guard be if it was ok to insulate inside of it?

    The reason the installer suggested putting the fiberglass inside the guard was to provide some air blockage between the heated living space and unheated attic. If I do not stuff fiberglass inside the insulation guard, heated air will easily move past the metal plate on the inside ceiling and up into the attic.

    What is the best way to handle this? Is the fiberglass inside the insulation guard ok? Thanks!

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  2. oconnor

    oconnor Minister of Fire

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    You must leave the insulation outside the insulation shield. Your chimney needs an air gap between it and any combustibles, and that is what the shield is for. There shouldn't be any air leakage from the room below if the shield is installed correctly. You might want to caulk the joint between the flashing and the pipe, as well as the flashing and the ceiling.
  3. ckarotka

    ckarotka Minister of Fire

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    I don't believe that there is fiberglass ins inside the double wall it's ceramic insulation. I made my own (insulation shield) out if a piece of aluminum coil stock to go around triple wall. That never gets hot maybe warm but that's a stretch even. it keeps the blown in insulation away though.
  4. MikeP

    MikeP Member

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    +1 to what cleanburning said

    And to add, the chimney is probably not insulated with fiberglass, but with a non combustible like rockwool etc. I would remove the insulation if it was mine.
  5. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Get the insulation out of there & install another
    storm collar to prevent insulation from getting in there.
    Your installer is a danger to his customers.
  6. PopulistWoodBurner

    PopulistWoodBurner Member

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    Thanks, folks. You would think the installer would know better. I will take the insulation out and also take the ceiling plate off inside the house and caulk around where it meets the ceiling to achieve an airtight seal there.
  7. CountryBoy19

    CountryBoy19 Minister of Fire

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    On a related note, would it be acceptable to put mineral wool or similar insulation in there? I've wondered this, because I have a considerable gap between my pipe and insulation shield (3/4") that I don't think I can fill with caulk. I'd like to stop the air leakage and insulate that as best I can.
  8. begreen

    begreen Mooderator Staff Member

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    WTF? Your instincts are correct. This installer needs to read the manufacturer's directions. The whole point of the insulation shield is to keep the insulation away from the darn pipe. I would look over every inch of this installation, starting with the roof section on the right side that appears to be closer than 2" to the pipe. It looks like he started cutting this board and then it broke loose, so he just stopped. What part of 2" from combustibles doesn't this guy understand?
  9. 98dingo

    98dingo New Member

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    I agree with everyone else. Remove that insulation and leave that air space there. If you put ANY kind of insulation there you are asking for trouble of some kind.
  10. vvvv

    vvvv New Member

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    the reason for not insulating & leaving airspace is to protect the pipe from overheating in that insulated zone so any insulation will do the same. fglass dont burn, it melts & turns to glass
  11. CountryBoy19

    CountryBoy19 Minister of Fire

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    Can you define "overheating" please? How hot is too hot? The reason I ask is that the inside of the pipe is made from the same metal as the outside, and the inside gets up over 1k degrees.

    Also, can you provide the source where you found this info?
  12. vvvv

    vvvv New Member

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    pipe is tested & certified @ 2100*f . if whole pipe reaches 2100*, the insulated area will exceed that..
  13. begreen

    begreen Mooderator Staff Member

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    Interesting physics, output temps>input temps?
  14. Highbeam

    Highbeam Minister of Fire

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    Your roof decking looks like mine which is basicly planks of 1x6 boards layed across the trusses. Your guy cut the decking to put in this chimney and his luck was bad. He managed to cut one of the deck boards right beside a butt joint and now that board is unsupported. When you go up there to sweep the chimney you might just find that unsupported roofing and put your foot into your attic. Not good. You'll need to do some framing up there to support the decking around the penetration. At the very least screw another chunk of lumber to the bottom of the decking running perprendicular to the deck boards to support that fallen board. Be sure to use screws that aren't too long that they poke through to the roofing.

    Remove the insulation from inside the insulation barrier. Air seal gaps below as needed. The guy cut the hole 3/4" too big? Sounds like you had a real winner out there.
  15. greythorn3

    greythorn3 Minister of Fire

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    this is why i dont trust people to install for me. if i do it i know whats been done. im so sick of these know it all kids nowadays, just waiting to get people killed with their professional installations.

    actually it looks as if that one roof board on the right is not 2" of clearance from the pipe. i would correct that if its not. would be awful to have a roof catch fire.

    [​IMG]

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  16. CountryBoy19

    CountryBoy19 Minister of Fire

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    I tried to understand it, I really did, but I just kept coming back to this^^^. How can the temp get higher than the temp in the chimney?

    Maybe I'll just call Simpson and see what they say about it.
  17. begreen

    begreen Mooderator Staff Member

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    Perhaps con - fusion?

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