We installed a ceiling fan in our bathroom. My husband had heard that if you put a loop in the ductwork it would keep the wind from coming back through the duct. The first winter the duct froze solid from all the moisture accumulating in the bottom of the loop. How should this be properly installed?
Answer:
All you need in that duct is a couple of elbows and not necessarily loops. If you insulate the duct heavily from the fan housing to the roof sheathing, you won't get condensation inside it. Wrap R-20 or 28 fibre bats around it loosely and use a lot of masking tape to hold it there but do not compress the insulation as it starts to lose its efficiency as soon as you compress even a bit.
