With five people showering in our house, there is a tremendous amount of humidity in our bathroom, even with the window open. I want to install an exhaust fan so I have some questions. There is currently a heat lamp in the ceiling which is where I will put the fan so electrical wiring is already there. I would like to vent out the soffit. How large should the fan be? What type of ducts should be used: solid plastic pipe or a dryer vent kit? Because of the lack of room in the attic, it would be much easier to use a flexible pipe. Should the piping be insulated after installation?
Answer:
The fan should be 110 CFM and it could be vented with the flexible plastic duct running under the insulation to the soffit where it is vented outside. If you have to run across the tops of the attic floor joists, you'll want to cover the duct with at least R-28 bats. I suggest using a pop-in type vent at the end of it with the louvers leading steam away from the house rather than pushing it back against the wall. The screen idea works well.
