Your first step is to head up into your attic. Yeah, I know. It’s dark, smelly, and full of itchy insulation but in the attic is where your answers will be found so suck it up and get up there. The biggest piece of advice I can give you is to make sure to walk on the tops of the ceiling joists and not on the drywall itself. If you walk on the drywall, you’ll end up like Clark Griswold in the 1989 classic Christmas Vacationexcept you likely won’t land on Rusty’s bunk bed.
Next, locate the exhaust fan duct that hopefully travels from the fan in the ceiling of your bathroom and terminates to the exterior. If it doesn’t terminate to the exterior you’ve got more problems but that’s for another blog post. So, in the interest of me getting another blog post out of this let’s just assume, for the time being, that the duct terminates to the exterior of your home.
After locating the duct give it a once over and if you can see metal that means it is not insulated and, well, there’s your problem. What’s happening is the warm moist air in your bathroom is being drawn through the fan and into the duct where it condenses inside the cold uninsulated duct and reverses course and drips back into your bathroom.
The fix is pretty easy…head to your local home improvement store and buy duct insulation and some zip ties. Then wrap the insulation around the pipe and attach it with the zip ties.
That’s all there is to it.