Mildew on Sheetrock Outside Ductwork


Old 06-14-13, 06:36 PM
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Mildew on Sheetrock Outside Ductwork

We installed central air in our house about 8 years ago. Our sunroom has two vents at the top of the wall between it and the garage. On the garage side of that wall, a lot of black mold runs on the sheetrock along the floor and then in two stripes up the wall, following the ductwork to the vents. I am sure it is caused by condensation - the hot air in the garage, and the cold air in the ducts.

Does anyone have any ideas what we should do? All I can think of is to cut out the sheetrock and leave the ducts exposed, but will water then just drip onto the floor?

I'm not very knowledgeable about this, and my husband doesn't think it's a big deal, but I am very worried about the mold, both for our health as well as for how it will affect the resale value of our home. Thank you!
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Old 06-15-13, 12:50 AM
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You need to remove the drywall using all necessary techniques to contain the mold. You then need to air seal and insulate the ductwork before replacing the drywall. Exactly how to accomplish this task depends on how the duct is currently installed.
Old 06-15-13, 10:34 AM
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How does the sunroom attach to the house? does the roofline meld with the main house, or is there a 2nd story that the sunroom roof originates out of? I lean more toward a roof leak at the flashing. It would also be helpful to know what type of siding is on the house. Another area to look into is if there are any plumbing vents in the roof in the general vicinity of the leak.
Old 06-15-13, 11:26 AM
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The sunroom was an addition to the house built many years ago on a concrete slab. You can enter it through the garage - it is two steps up from the garage floor. About 8 years ago, when we added central air, we enlarged the sunroom, extending it 5' into the garage. When the addition into the garage was framed out, there was a tunnel under the floor through which the ductwork for the AC runs from the basement. Two ducts run up to vents about 13 feet up, from the duct that runs along the floor. The mildew definitely follows the ductwork.

Furd, I think you're definitely on the right track, but is this something that we can do ourselves, or should it be done professionally? The ducting is just those big silver, squishy tubes (you can tell I'm just a homeowner...). And I don't know what "airseal" means, or what we would insulate with.

As I said, my husband thinks it's "no big deal", but I'm worried about it. It gets a little worse each year. Needless to say, his workbench and all sorts of stuff is stored/hanging on the back wall of the garage, which is the common wall with the sunroom.

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