I have a bathroom exhaust fan that is vented into the attic, up to the ridge-vent area. Since the weather had gotten colder, water drips back into the bathroom from the fan after it has been on for a while. Do I need a certain type of material for the vent? Should I insulate it? I’m not sure what the solution is. Thanks for your help.
Your problem is condensation in the cool fan duct. Warm, moist air from the bathroom condenses on the cool duct and runs down the duct to the fan. The duct is now cold because the attic is cold.
The duct should be insulated. Make as short of a run as possible to a vent connector through the roof deck. The fan duct should not be run to the ridge-vent. You can find insulated duct and a vent connectors at a building supply store.
The fan and the vent connector through the roof should also have a damper that closes when the fan is off to limit air movement.