combined intake air flows through blower 42 and into heating and cooling elements in conditioner 40 through duct 32 into humidifier 38 for maintaining a predetermined relative humidity the heater elements not shown in conditioner 40 may be electric or gas type elements common in the art or any other suitable heating elements the cooling system not shown in conditioner 40 may be a conventional compressor condenser type system alternatively a heat pump system may be used for heating and cooling the air as may other suitable systems guidelines for selecting the predetermined relative humidity are available in published documents of the american society of heating refrigeration and air conditioning engineers ashrae standard 62 1999 ventilation for acceptable indoorair quality which indicates that the relative humidity should be maintained below about 70 to inhibit fungal contamination including but not limited to molds and mildew the actual relative humidity and air flow requirements will be structure specific and are determined using procedures and standards known in the art the conditioned air flows through duct 33 and into interior space 50 and as previously described exhausts through vents 34 into attic 36 the addition of the outside makeup air 44 to the air volume existing in the essentially sealed structure creates a suitable positive pressure in the structure 30 and attic 36 relative to the outside environment and causes conditioned air to flow 16 through the air flow passage 17 in the outer wall 25 in one aspect the blower 42 may operate continuously or substantially continuously forcing an essentially continuous flow of conditioned air.