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Air Sealing around cathedral ceiling box

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by NBABUCKS1, May 20, 2013.

  1. NBABUCKS1

    NBABUCKS1 New Member

    Joined:
    May 9, 2013
    Messages:
    31
    Loc:
    Kodiak, AK
    I am doing a chimney install and need to air seal around my cathedral ceiling box. Can I use this product? http://www.touch-n-seal.com/gunfoamII.htm

    I plan on running double wall pipe (DVL to Double wall chimney) for the span and the my cathedral ceiling is 15 feet above my stove.

    The stove will run into the cathedral ceiling box. I want to air seal around the box. What type of external temperatures will the box have?

    My main concern is the polyischonerate that is near the box. I am insulating below my rafters with a layer of polyiso. Polyiso is very flamable.

    Is there some kind of insulation/firebreak that I can put around the box above the drywall and below the roof deck?

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  2. webby3650

    webby3650 Master of Fire

    Joined:
    Sep 2, 2008
    Messages:
    5,122
    Loc:
    southern Indiana
    You can put any kind of material around the outside of the box. The box maintains the proper clearance to combustibles, no matter what they are made of. At the roof, it will be more difficult. Can you build a sheet metal chase from the box to the bottom of the roof deck?
    Keep in mind that the box itself isn't air tight. You will want to seal all the corners and seams on the box from the inside.
  3. jdp1152

    jdp1152 Minister of Fire

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    777
    Loc:
    Massachusetts
    fire rated caulk, rockwool insulation in the immediate area.
  4. webby3650

    webby3650 Master of Fire

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    Loc:
    southern Indiana
    100 degrees or less. So, there is no need to do anything special.
  5. Highbeam

    Highbeam Minister of Fire

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    Dec 28, 2006
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    9,878
    Loc:
    base of Mt. Rainier on the wet side, WA
    I sealed with regular caulk around mine. That's the point of the box, to maintain clearance to the pipe.
  6. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
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    52,952
    Loc:
    South Puget Sound, WA

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