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  1. #1
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    I just purchased a new home (approx 15 yrs old)that has 2 fireplaces (one on the first floor and one in the basement directly below). When I light the fireplace on the first floor, smoke eventually travels down into the basement through the downstairs fireplace flue. Each fireplace has a separate flue (clay tiles) which run parallel inside a brick chimney built on the outside rear wall of the house (goes up past the roof). The first floor chimney flue exits the chimney about 8" and the basement flue exits about 16" above the top of the chimney. The downstairs fireplace seems to have been converted to a top mounted damper located outside on top of the flue (leads me to believe there may have been some type of backdraft problem). I had a chimney sweep come and he indicated that I probably had cracks in the flues and had smoke infiltration. This is a very expensive fix and I was wondering if it could be due to the fact that the flues were in close proximity and the smoke was entering the downstairs flue from the roof. The amount of smoke seems to lessen when the downstairs top damper is open which would seem to shoot a hole in my previous theory.

    Any thoughts would be appreciated.

    SGB

  2. #2
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    Have you tried opening a window while testing? This would help determine if you are putting the house in neg. pressure when you use the fireplace. If this helps, you need some makeup air for the place.

  3. #3
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    Thread Starter
    When I lit a fire last Thursday, I opened several windows on the first floor.

  4. #4
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    did it help at all?

  5. #5
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    No, it was about the same as when no windows were open. Is it possible that smoke migrating betwen cracks is both flues? Again, the fact that the one fireplace was retrofitted with the top damper leads me to believe that it may be an air pressure issue.

    SGB

  6. #6
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    Does the problem reverse when you light the basement and not the first floor?
    If there are cracks that are causing this, it should show up regardless.
    Is the basement closed off with a door from the rest of the house?
    Are the other parts of the physical plant in the basement? gas or oil furnace/boiler-water heater? Where do those vent?

  7. #7
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    Thread Starter
    I have never lit the basement fireplace.

    The basement fireplace is in a large room that is open to the rest of the basement including the stairway to the first floor.

    The furnace room is downstairs and both gas furnaces and the gas hot water heater are vented thru 2 separate flues out a separate chimney.

    Any thoughts on why the original damper would have been removed from the basement fireplace and replaced with a top damper?

    Thanks for all your help!

    SGB

  8. #8
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    Cool classic case

    Your situation unfortunately is a classic. The top damper was installed in an attempt to prohibit smoke from recirculating back into the home. However, if the cable has any slack, smoke can get entrained in.

    The flues are staggered backwards: extend the upstairs Fp higher than the basement one.

    If you think you have cracked flue tiles, you have a lot more to worry about than just smoke. You might burn your house down! I strongly recommend you get a Level II inspection with video scanning. This isn't fool proof but can spot visible defects you can't looking up or down a chimney. If smoke is shunting from one flue to the other reline it before you burn another fire! Yes, listed liners are very expensive but it sure beats the house burning down or CO poisoning.

    The issue of smoke sucking down the basement Fp is one of pressure regimes. Fix the house and the fireplaces will behave. You have upper level leaks and mechanical exhausts that together are more than the passive infiltration of air down low in the home. Seal the upper levels as tight as Tupperware then provide some relief down low. Opening windows above the Neutral Pressure Plane will only exhaust more air exacerbating the problem.

    HTH

  9. #9
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    Hearthman:

    That was very helpful. That would explain why we get smoke regardless of whether the top damper is closed or not. Couple of follow-ups.

    1. Currently, the basement flue is about 8"-12" higher then the 1st floor flue. Can the 1st floor flue be extended such that it is higher then the basement flue? If so, how much higher should it be in order to overcome the "suction" created by the other flue?

    2. Can you explain further what else may be causing the pressure imbalance within the home and what can be done to resolve?

    Could the flue height differential be the sole cause?

    Thank you very much.

    SGB

  10. #10
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    tests

    remove that top damper and silicone a piece of sheetmetal over the flue tile. Next, add a 2ft length of flue tile to the upstairs flue using silicone (temporary). Try & see.

    Open windows, can ceiling lights (esp. non-IC rated), registers or any penetrations in ceiling, attic access. etc. should all be verified tight using smoke.

    Don't use mechanical exhausts during burning

    Open a basement door or window.

    If you have forced hot air heating, duct leakage can be hugh. In the basement, seal the return ducts, esp. the filter slot. In the attic, check each joint on the warm supply, esp. flex hoses.

    You can have adverse wind effects adding to it. However, even if you drilled a hole in the wall btw flues, it should not shunt smoke down the unused flue. This tells me you have a pressure gradient driving this phenomenon.
    hth


  11. #11
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    Thread Starter
    Hearthman:

    It sounds like the taller flue may solve the problem. When I had the chimney cleaned earlier this year and told them of the problem with the smoke,they indicated (through visual inspection) that there were cracks. However, I was and am suspect as to their conclusion as the top damper was probably an attempt to fix this problem previously. I can't think of any other reason that the original damper would have been removed and replaced with a top damper.

    How would I go about finding someone such as yourself who is very knowledgeable and can help me put this issue to bed once and for all. I live just outside of Baltimore.

    Again, many thanks

    SGB

  12. #12
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    Hi SGB, I too live outside Baltimore and am having your same problem with my new house. Smoke from my upstairs fireplace is coming into my basement. How did you resolve your problem and can you recommend a good contractor in Baltimore? Thank you!

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