We are having an unseasonably cold fall here in Anchorage (yeah right?!) with lows in the single digits. At these temps, there is water that drips out of the stove vent and bathroom vent. I assume it is condensation from the warm house air hitting the cold air in the vent pipes, but is there something I can do to stop the dripping? It even happens when the fan has not been on.
Warm, moist air from the interior can rise through exhaust vents in the kitchen and bathroom, and condense inside cold exhaust vent pipes in unheated attic space. This condensate is what is running back down through the exhaust fans, of course.
To help prevent this condensation, you can wrap insulation around the vents in the attic and use duct tape to hold it in place. Don't wrap it too tightly or compress the insulation too much, as this will defeat the insulation purpose.