Since there is no window in the basement bathroom, I’m adding an exhaust vent to it. I’m using a 90 CFM fan which is rated at 0.5 somes (which is almost silent) – although I’m putting it through 3″ duct instead of 4″, which I believe drops the rating to 80 CFM (still more than enough) and makes it slightly louder.
Of course the exhaust air needs a place to go, so that meant adding a new vent. One thing I learned: big drill + putting a hole in the side of the house = extremely nervous girlfriend. I used a 3.25″ hole saw, which did the job nicely.
I used flexible duct, and some foil tape and clamps to keep everything together. It’s starting to get crowded in the electrical closet as you can see.
The outside vent and the fan itself both have dampers built-in, so I’m hoping I won’t have any issues with cold air coming down. I’ve checked on a couple of cold, windy day’s we’ve had lately, and can’t feel anything so it looks promising. In my old apartment, the exhaust fan either had no damper (or it was broken), and it was very awful during the winter to feel the -20 degree air blowing on you (right above the toilet) first thing in the morning.