At the end of the day there are really only two causes for condensation on ductwork: improperly insulated ductwork and excessive moisture in the air. Both of these are easily treatable. Remember that condensation can cause all sorts of problems, from leaks to mold infestation so take the time to address this problem as soon as you can. When the time comes or if you have the money, the best thing that you can do to solve this problem is to just have your air ducts replaced with modern ductwork that includes insulation and a vapor barrier built-in. If you don’t live in the Santa Clarita or Greater Los Angeles area, or are still in the research stage then I’ve included a guide on how to find a reputable contractor in your area: How to Choose a Contractor . I hope this article has helped solve your sweaty duct problem. For more information on other related air conditioning and heating topics, visit our ASM Air Conditioning Blog .
From just the photographs, and without having inspected the building exterior, roof, nor other areas, the photos look like a roof that had numerous leaks, perhaps from worn out roofing, possibly even some rotting sheathing. The photos show areas of apparent mold on some rafters. But especially in the 2nd photo at above right, the very extensive condensation stains around the nail protrusions through the roof deck tell us that the whole attic interior has been soaking wet. Now for the big question: is this wet attic caused by roof leakage or is there a building water entry problem?