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  1. #1
    Join Date
    Oct 2019
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    4
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    Air Duct in Basement Closet Sweating with AC and Heater

    I live in a very old house. Its one story, but with a half-above-ground basement. For the past year, I have noticed mold growing in my basement closet where I keep my clothes. I have finally pinpointed the problem area.

    Please see the attached image. Item A is a vent where the AC (or heater) air passes through. Item B is a vent that pushes out air. It appears that Item B leads to a crawl space under the house.

    During the summer, I often found Item A being very cold (cause of the AC). Item A and the surrounding wall was wet from condensation (I’m assuming AC sweating).

    So far, during this fall, when the Heater is running, Item A is warm and dry. Item B is also dry, but the wall below Item A and surrounding Item B is damp.

    What can I do here to stop this condensation and keep my entire closet dry? I am tired of the mold getting into my clothes.

    Note: I also have those Hanging Moisture Absorbing bags in my closet that absorb water in the air. During the summer, the bags absorbed a cup of water within just three weeks.
    Attached Images Attached Images  

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,223
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    Get 1 or 2 small dehumidifiers and run them 24/7

  3. #3
    Join Date
    Aug 2002
    Posts
    2,593
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    It sounds like your crawspace is not sealed and insulated properly with a proper vapor barrier.

    Do you have crawspace vents on the exterior walls? Are they opened or closed?

    Are the crawspace walls exterior insulated and sealed?

    Is the crawspace floor sealed with plastic?

    Does the crawlspace have a sump pit? Does the sump operate?

    You may still need a dehumidifier in the closet but you most likely also have a crawlspace issue that needs attention.

  4. #4
    Join Date
    Oct 2019
    Posts
    4
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    Thread Starter
    Thank you for your message Advanced Response.

    I just opened Item B and took some pictures.

    The first two images display what is inside the crawlspace. Just some junk.

    Name:  Inside Crawlspace 2.jpg
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Size:  87.8 KBName:  Inside Crawlspace 1.jpg
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    The image below is showing a hole leading directly into the air duct (Item A)

    Name:  Image 1.jpg
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    Image 2 shows the length of the air duct (Item A)

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    Image 3 shows the air duct (Item A) attaching to the wall of the from within the crawl space

    Name:  Image 3.jpg
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  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,223
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    Ideally
    Seal the crawl space
    Insulate the ducts
    Insulate the floor joices
    Dehumidify

  6. #6
    Join Date
    Oct 2019
    Posts
    4
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    Thread Starter
    For sealing the duct, does this include the Item B vent? Should I also seal the exterior crawlspace vent?

    In regards to insulating the duct, can I insulate just the part in my closet (dry wall)? Can I use this? amazon.com/VIVOSUN-Insulated-Insulation-Bubble-25-Feet/dp/B0739ZSW17/ref=sr_1_22?keywords=Duct+insulation&qid=157118103 0&s=hi&sr=1-22

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,223
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    No
    You hire a contractor to do the work.

  8. #8
    Join Date
    Jun 2003
    Location
    Texas
    Posts
    1,494
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    looks to me like yur sucking air from under the structure into the conditioned space? no beuno
    Last edited by poppa; 10-15-2019 at 09:25 PM. Reason: s

  9. #9
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,701
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    Condensation on a cold surface, check the temp/%RH? dew point of the air on the wet side. If living space needs to be <50%RH most of the time. If not better dehumidification is required. Adjust the a/c to maintain <50%RH during significant cooling loads, usually slowing the air flow through the a/c coil. Plus adding supplemental dehumidification to maintain <50%RH during evenings and rainy days.
    If <50%RH and ducts sweat add insulation with vapor barrier on the wet side. 1/2" of closed cell foam on the on the damp side of the cold surface should be like icing on a cake.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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