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"Millboard" - The Truth!

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by jtp10181, Aug 25, 2007.

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  1. jtp10181

    jtp10181 Minister of Fire

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    While working with an R & D guy this week we accidentally found a reference to the "millboard" that is so mysterious in the Quadrafire stove manuals. This is from the newest UL 1618 in regards to "Ember Protectors 2".

    "The subcommittee has chosen R=0.45 as the minimum thermal resistance required. This value comes from the long accepted benchmark of 3/8" of asbestos millboard with a k-value of 0.84."

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  2. begreen

    begreen Mooderator Staff Member

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  3. nshif

    nshif New Member

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    But Quadrafire says 3/8" with metal clad so what R value is that? I gave up trying to figure it out for my 4300 and put down 1/2 " cement board with 2x4 metal studs on top with 2 more layers of cement board over that capped ( soon ) with 2+ " of ceramic rock. It better be enough cause I aint tearing it out!
  4. begreen

    begreen Mooderator Staff Member

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    The metal cladding doesn't add to the Rvalue, it protects the millboard with a non-combustible surface. You did well and are ready to go, even if you switch to a stove with a hotter bottom.
  5. nshif

    nshif New Member

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    Thanks BG I needed that vote of confidence, as long as the inspector sees it the same way.
  6. jtp10181

    jtp10181 Minister of Fire

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    I knew we talked about it before, and no one (not even me or other Quad dealers) really knew what they were talking about. I also posted not too long ago that someone at Quad told me anything non-combustible at least 3/8 thick would suffice which is not really true. I just wanted to clear the air.
  7. hearthtools

    hearthtools Moderator Emeritus

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    All the travis manuals just say 3/8 Non combustable
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