Abstract: A system and method for regulating humidity in an enclosed structure, including an outside humidity sensor; an outside temperature sensor; an inside humidity sensor; an inside temperature sensor; a ventilation system; and a computing unit that receives sensor information from the temperature and humidity sensors, compares sensor information from inside and outside the enclosed structure, and utilizes the comparison of sensor information to generate one or more output signals to control the ventilation system. This ensures that supply ventilation (by outdoor air) is activated only when it is beneficial for the drying of the attic and controls the ventilation so that an acceptable moisture level is ensured with a minimal ventilation rate, resulting in a warmer attic and reduced heat loss during the heating season.