A. Mike Strom: The one way to vent your bathroom is by opening a window or skylight if they exist. Being in the Chicago area in the winter not too many people open windows for ventilation. The best year round way to vent your bathroom is by an exhaust fan. Building codes require minimum 50 cfm intermittent ventilation for bathrooms. A rough rule of thumb for sizing the exhaust fan is to calculate the square footage of the bathroom. Eight feet wide by ten feet long equals eighty square feet, you need 80 cfm fan. Exhaust fan should be turned on before starting shower and remain fifteen to twenty minutes after turning off shower. You can select an exhaust fan that has a timer or has a humidity sensor. Placement of the fan will also make a difference in performance and should be closer to a source of humidity generated.
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