The enclosed ventilation system is designed in a way that could experience condensation when the outside temperature is significantly lower than the air inside the room. It is therefore crucial to ensure proper venting of the room specially in the case where the room is used for bathing, showering etc. Exhaust fan will only conflict with Classic and Propane models as the Comfort is a two-pipe system and will not be affected by exhaust fans. We recommend the Comfort model for colder climate areas.