Abstract: Passive dehumidification ventilator for crawl spaces and attics of dwellings. According to the present invention, dehumidification is accomplished for the attics and crawl spaces of dwellings by providing entrance tubes for circulating air in these regions. The tubes are constructed such that cooler incoming air through the center of the tubes causes condensation on exterior surfaces of moisture that is contained in the air of an attic or crawl space. This moisture is then conveyed exterior to the building so that it is not reintrained in the air flow. Since moisture is reduced by condensation, a lower air flow is required to reduce the moisture content, and thus the heat load of the heating system is reduced thereby. In a soffit unit, a plurality of tubes direct air into the region adjacent the roof structure such that moisture ladened air flowing down the inner surface of the roof condenses the moisture therefrom on the exterior of the tubes.