Joined: Jul 2017
Posts: 83
Insulate the duct run in the attic.
11/10/2017 at 1:06 PM
Water forms when you have hot inside air contacting cold outside air. The problem is not likely coming from the roof top. It's likely an uninsulated duct run in the attic space where cold attic air is contacting hot air in the duct, condensing on the inside of the duct and running back into your home. Most fans have a "damper" that closes when the fan is not running, isolating hot air from the duct run. Make sure the damper is installed, or that the duct run has insulation in the attic, all the way to the roof top. Make sure the roof top cap is not frozen shut or open, and is clear of snow.