hi folks, our bathrooms each have one window that open onto semi-enclosed light wells. odors and humidity stick around if the bath doors are closed, so we want to increase airflow. in-wall fans would be right next to the existing windows, make noise, and require a bunch of electrical work, so we haven’t jumped at the chance to install them.

what about venting upwards to the (hip and valley) roof? even a small a stack effect might do the trick. a wind-powered turbine is also a possibility. the location is central california and so a little heat loss is OK, though the turbine is probably excessive. i don’t have a clue how much cross-sectional duct area might address the problem. there’s no advantage to a vent near the floor, right? what do you all think?