I put these in both bathrooms a couple years ago. Similar to your idea, I think. 6 or 8 inch duct. Fan's on the roof. http://auravent.com/bath-fan.html
Works great, almost silent. I installed timers so they wouldn't run all the time. If you wanna go conventional, Panasonic makes a nice fan.
Last edited by ratherbefishing; 05-27-2015 at 12:43 AM.