Ductwork condensation & mildew
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  1. #1
    Join Date
    Feb 2005
    Posts
    6
    What would be the main reason for insulated ductwork in a 4-5 foot crawl space dripping condensation be? The ductwork also has white powdery mildew on it. Would it be because of loose ductwork, high humidity inside the house, dirty coils?? Any help is appreciated.

  2. #2
    Join Date
    Jun 2004
    Location
    Florida
    Posts
    556
    could be high humidity in the crawspace. Do you have a vapor barrier on the ground? Is there a creek that runs through the crawspace or any standing water? Is the ductwork internally or externally insulated?

  3. #3
    Join Date
    Feb 2005
    Posts
    6
    The crawl has plastic vapor barrier. I corrected a drainage problem from the rear of the house where water was running down hill and collecting in the crawl. (Also had the rear deck removed from the house and had to replace sill plates and sister some joist because of water damage.)
    There are 2 automatic temp vents exhausting the crawl & all the vents are open.

  4. #4
    Join Date
    Feb 2005
    Posts
    6
    The ductwork is wrapped externally where it branches off the main duct. The main duct is lined inside/outside.

  5. #5
    Join Date
    Jun 2004
    Location
    Florida
    Posts
    556
    how long ago did you correct the drainage problem? It may take a while for the crawspace to completely dry out. You should take some humidity readings in the crawspace to see what it is.

    Is the white mildew on the internally lined duct. If so, it is probally just water deposits left after the condensation dried.

    [Edited by dhanna on 02-22-2005 at 12:35 PM]

  6. #6
    Join Date
    Feb 2005
    Posts
    6
    The drainage problem & repairs were done a couple of months ago. The white powdery substance is on the outside of all the ductwork. There was some white mildew (dry rot?) on some joist as well. We've just had ALOT of rain and I was in the crawl yesterday and there was no significant sign of standing water. I did not check ever square foot though.

  7. #7
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    Is it a vented or non vented crawl?
    How tall are you Private???!!!!

  8. #8
    Join Date
    Feb 2005
    Posts
    6
    Vented.

  9. #9
    Join Date
    Feb 2005
    Posts
    6
    Forgot to mention that the condensation was occuring when the A/C was on. There is no condensation when the heat runs.
    This is most likely a summer/high humidity related issue.

  10. #10
    Most condensation occurs when you either have air leaks, broken vapor barrier. I have also seen this problem when the unit was not moving enough air and the discharge was so cold in relation to the ambient temperature that it caused the duct to sweat. Usually it can be traced to either air getting out of the duct or the vapor barrier being broken.

  11. #11
    Join Date
    Sep 2004
    Posts
    3,157
    Why would you have so many other water problems in -under and around your house and not expect that the mold and condensation you have found are not caused by the same wet conditions. and that you must first dry the area before it will go away. And it will only get worse untill you dry the area

  12. #12
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    The temp of the duct is lower than the dew point in your crawlspace.
    A vented crawl is nothing but a rain forest in the summer.
    The only way to remedy this problem in to have the crawlspace sealed and throw in a dehumidifier.
    How tall are you Private???!!!!

  13. #13
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    High humidity in the crawlspace, the ductwork is below the dewpoint and it sweats, do a google on crawlspace encapsulation, Ive seen houses where this has been done, every house in a hot,humid climate should be done this way

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