MOLD problem in vents, help please
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  1. #1
    Join Date
    Aug 2005
    Posts
    3
    We had a TRANE XL 1400 installed about 1.5 years ago. We have discovered black mold in all of the downstairs registers. The company that installed it has said that it's probably the speed of the exhaust fan needs to be increased. That didn't sound right, so I had another company come and inspect the system. They measured the humidity level inside each register, both with the system turned on, and with it off. With it off, it was close to 100%. With it on, it was 86% humidity. The inside house humidity was about 50%. He said that he believes that the distribution box under the house is too small, because it was sweating. The upstairs registers I don't see any mold.

    Should I have all of the duct replaced? The original installer said they would run through some substance that will kill the mold. I'm not comfortable with that.

    Thanks in advance for any advice.


  2. #2
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    Did the original intallation company run a Manual J load calculation?

    If not I would pay someone to.

    If the system is too large, cleaning the ducts will not solve your problem.
    How tall are you Private???!!!!

  3. #3
    Join Date
    Aug 2005
    Posts
    3
    I know they did some type of assessment, but not sure what it was. We were going to go with the XL1200 model, but since the XL1400 offered two speed fan and a better warranty, then we went with the XL1400. We live in Raleigh, NC, in a two story, 1445 sq ft home.

    Is there a specification on how big the duct work and distribution/return boxes need to be for this particular TRANE model? There are 7 registers in our downstairs.

    thanks...

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    the calculations are not brand specific.
    lower fan speeds are best for humidity control.

    any ducts outside of the conditioned space should be sealed with mastic then insulated!

    again, get a manualJ calculation, then insist that the ductwork be sized per manualD, and the equipment be sized per manualS!

    50% humidity usually does not support mold growth.

    clean the ducts at the elbows with Grandma's lye soap & h2o! maybe spray with 30% bleach solution first, let it sit for 15- 30m, then soap. of course, you will vacuum the elbows before all of this -- use a shop vac, or your sweeper attachment.

    change your filters more often!
    upgrade to a 4+ inch thick media filter! ASAP!

    such a small house should have a small a/c! what capacity is yours?

    seal off the crawl space -- plastic on floor -- read at BUILDINGSCIENCE.com

    [Edited by cem-bsee on 08-17-2005 at 09:57 AM]

  5. #5
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    The only way to know is to run a Maual J & D on your home.

    If you have mold all through your ductwork, it is likely not caused by some distribution boxes.

    How tall are you Private???!!!!

  6. #6
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    I am a homeowner and therefore would not be expected to know as much as a pro. But I have some experience I want to pass along. Last year I bought a "duct sealing" job which mainly involved caulking between the ceiling and supply vent boxes. Where they found a bit of black mold at the supply, they claimed that was evidence of an air leak between the attic and building envelope.

    I have no reason to disbelieve them. Does this sound like your problem at all? If nobody has made sure of air sealing between house and attic, that is something that needs to be done.

    Hope this helps -- P.Student

  7. #7
    Join Date
    Aug 2005
    Posts
    3
    The contractor wants to use a product called "Defend". Is this a safe product that kills mold?

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