the humidity level in attic 10 reaches 65 relative humidity and deactivates the fan motor when the humidity level is lowered to 61 relative humidity fan unit 22 also includes a heating element 36 which is located above fan 30 and which is similarly activated by humidistat control 34 to heat and temper the air which is drawn by the fan and expelled through housing 26 into the home living quarters 20 in the use of the vent system of ths invention heat and moisture from living quarters 20 rises upwardly through ceiling 24 by conduction and through ceiling shutters 18 by convection increasing the moisture level in the cooler temperatures found in roof cavity 10 as such moisture accumulates the humidity level rises until humidistat control 34 activates fan motor 32 and heating element 36 fan 30 draws drier air from the outside into roof cavity 10 through temperature responsive vents 14 fan 30 also simultaneously draws warm air from living quarters 20 into roof cavity 10 upwardly through ceiling shutters 18 the mixture of air drawn into roof cavity 10 is preferably 80 outside air and about 20 air from living quarters 20 as the dry outside air is mixed with the air already within roof cavity 10 and the warm air from living quarters 20 the relative humidity of the air mixture in the roof cavity is lowered to reduce condensation this air mixture is drawn through cylindrical housing 26 by fan 30 heated by heating element 36 and expelled into the home living quarters 20 in this manner the humidity level in living quarters.