Duct Work Creature in the Night
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  1. #1

    Duct Work Creature in the Night

    My problem is an eerie sound emitting from my duct work that is within my concrete slab. When the furnace starts blowing warm air through the duct work, I believe the 10” round duct work expands and contracts sounding like there is a woodchuck trapped under my floor trying to chew its way out.

    My split entry home is located in Wisconsin where we do have cold winters. The furnace is a Lennox Pulse distributing heat through conventional duct work in the upper portion of the house, but in the walk out basement where there are two bedrooms and a bath that receive there heat from the duct work that was buried under the concrete slab. The routing of the duct work travels approximately 15’ from the furnace (with on opening to supply heat to the bathroom) then goes into a tee with each run (one left/one right) to each of bedrooms that are approximately 10’ from the tee in both directions.

    The contractor is no longer in business that installed the system and this was the first hybrid system that utilized conventional ducting with in ground ducts. I need to resolve this situation as my eight year old granddaughter is sacred to sleep in the bedroom with sounds being made from the creature from beneath.

    Are there options anything short of jack hammering the floor? My friend has this same setup, but instead of using a metal duct, his ductwork is PVC that doesn’t creak in the middle of the night.

  2. #2
    Join Date
    Mar 2003
    Posts
    7,321
    I would try leaving the fan in the on position to see if that makes it go away. While it may cost you a tad more to run the fan as opposed to cycling it with a call for heat, it could possible stop this from occurring. If you had a newer programmable tstat, you could theoretically set it up to be in auto during the day, and then on during the time when she is trying to go to sleep, say from eight to midnight. Once she is sleeping you could return it to auto. A good stat will have four periods to setup and could easily handle the change. The real issue is does this make it go away?

  3. #3
    Join Date
    Jul 2008
    Location
    Alabama
    Posts
    658

    under water?

    ive seen several systems like this with water in the ducts. the noise may be the water splashing in the ducts. you can get it out with a sump pump.

  4. #4
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,686
    has it always done it or is it something new?

    does it do it anytime the fan runs or just with heat?

    might be able to have a duct cleaning co send a camera down the duct to see if something is loose or stuck in the duct......

  5. #5
    In response to the duct work noise just starting recently, no it has always made this sound from day one. The system was installed 20 years ago.

    I'm sure that it isn't water in the duct.

    The installer did add rigid styrofoam to box in the duct work. I was thinking about the putting a camera in the run. I suspect that it is a seam either laterally or where the joints meet that is the origin of the noise.

    Thanks for the replies so far. If it is a seam causing the noise what are some of my alternatives?

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,273
    Quote Originally Posted by royboy91 View Post
    In response to the duct work noise just starting recently, no it has always made this sound from day one. The system was installed 20 years ago.

    I'm sure that it isn't water in the duct.

    The installer did add rigid styrofoam to box in the duct work. I was thinking about the putting a camera in the run. I suspect that it is a seam either laterally or where the joints meet that is the origin of the noise.

    Thanks for the replies so far. If it is a seam causing the noise what are some of my alternatives?
    If it is round metal ducting that was cast into the concrete slab, it is likely expanding radially as well as lengthwise when the metal heats up. The sound you hear is the metal placing pressure on the surrounding concrete, and slipping on it as the duct expands lengthwise.

    A possible solution is to have a product like "aeroseal" or some such applied to the metal walls of the duct, which might provide a margin of insulation and buffer to the expansion/contraction issues. Kind of a gamble, IMO.

    The ultimate remedy is to abandon the slab ducts and have overhead ducting installed in furdown chases or the like. Not cheap, but it will end the problem.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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