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  1. #1
    Join Date
    Mar 2011
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    Adding Heat Duct Behind Fireplace Box

    I have a house that is about a year old now and this is our first winter in the house. We have a Direct Vent fireplace which is installed in a cavity that extents out of the main part of the house. It is well insulated and there seems to be some (not a lot) cold air comming into the space. I have taken the mantle apart to see if there is any air leaks in the system and doesn't seem to be. I did notice that when i had it apart it was not a cold becuase there was warm air from the house going into the space. I was wondering if it would be ok to take and put a run from my furnance (which as enough capacity) into that space to add a little heat to the backside of the fireplace.

  2. #2
    Join Date
    May 2005
    Madison, WI
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    If there is a cold draft coming out of there, there is probably a leak someplace.

    Also if the interior wall between the room and the fireplace chase was insulated, removing that insulation will help the chase temper with the room itself better.

  3. #3
    Join Date
    Aug 2004
    S.E. Pa
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    One minute you have cold air infiltration, the next you have warm air exfiltration---which is it?

    Your chase may or may not be well insulated but if there is air movement then it is not welll air sealed.

    The insulation should be in the outer three walls--not just over the header. Puilling the mantel should have no effect on air movement. Did they leave off the drywall behind the mantel? If they packed insulation around the fireplace such as btw the framing and the standoffs and nailing tabs, it is a fire hazard and must be removed.

    I would not run a duct into this space. The clearances off the fireplace will be violated and you don't have a return. There's no need to condition this space if the outer walls are properly weatherized.

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