An exhaust only ventilation system is where one or more fans (generally bath fans) is used to exhaust air from a house (generally 24×7 though some are on timers) and make-up air is supplied “passively” (i.e. through cracks & holes in the walls, through insulation, critter dens, etc…). This type of vetilation strategy is used primarily in cool dry climates and creates a slight depressurization of the home; if you have any naturually drafted appliances this is definetly not a smart approach as it can cause issues with backdrafting. A far superior system is utilizing a “balanced ventilation” approach.
