Wrapping fireplace duct in cold air space

Discussion in 'HVAC Heating & Cooling' started by jmpage2, Mar 24, 2021.

  1. jmpage2

    jmpage2 New Member

    Joined:
    Jan 22, 2020
    Location:
    Colorado
    Hi experts,

    I have a gas fireplace that was re-ducted through a patio addition that was put on my home nearly 10 years ago. The original vent was re-worked and it was extended maybe 20-30 inches through the new patio soffit and a chimney installed.

    Water is pooling under the chimney and destroying the soffit but only seems to happen after we get a heavy snow and it sits on the roof for a while without melting.

    The roofing company said that this is due to the duct being in a cold space and condensation forming on the pipe and dripping... typically when there is a lot of snow on the roof creating an insulating barrier for the space and creating an ideal scenario for condensation to take place. Roofing company recommended using appropriate insulator around the pipe, especially at the elbow to stop it from condensing and dripping into the patio cover.

    I've talked to a few HVAC companies and they don't want to touch this and wrap the pipe so it looks like I might have no other choice than to do it myself.

    Can anyone tell me what kind of product is appropriate and safe to use for this application?

    Thanks.
     
  2. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Your writing about the flue and what size is it?
     
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  4. jmpage2

    jmpage2 New Member

    Joined:
    Jan 22, 2020
    Location:
    Colorado
    I don’t believe I can find that out without opening up the space by cutting into it, which I have not yet done. Probably 6” or 8” though based on the way it’s laid out with the chimney.
     
  5. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Is that part of the soffit vented ? I don't think the entire attic is vented might need to vent the chimney chase. Chimney sweep companies are good with this type of problem.
     
  6. jmpage2

    jmpage2 New Member

    Joined:
    Jan 22, 2020
    Location:
    Colorado
    That's a good idea, I assumed chimney sweeps wouldn't touch this since it's for a gas fireplace.

    The roof is vented with two large mushroom cap vents including one that's close to this area but when they get covered in snow it can't vent and that is likely contributing to the problem.

    Since we can get 20+ inches of snow on it a vent extension is not realistic.
     
  7. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Gable end vents.
     
  8. jmpage2

    jmpage2 New Member

    Joined:
    Jan 22, 2020
    Location:
    Colorado
    I already have vents at the very end of the soffit but they might be too far away from where the flue is for it to help.

    Large gable end vents though could possibly resolve the problem. I will see what the roofing guys think about this. It occurs to me that the reason the problem happens when it snows a lot is that the roof cap vents are getting covered up and that's causing the space to heat up enough for the flue to start condensing.
     
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