The Columbia County Habitat for Humanity Passive Townhouses are the first Habitat homes in New York State designed to achieve the Passive House standard, the world's most advanced building science benchmark for energy efficiency. Heating energy use in the Townhouses is expected to be 90% less than conventional construction. Air quality in Passive Houses is also significantly higher than in conventionally built or renovated homes because of the Energy Recovery Ventilating (ERV) systems that complete the Passive House designs. Air-tight construction is a hallmark of Passive House design preventing the drafts and air-leakage that normally reduces the ability of a building to achieve a high-performance in energy conservation. Built by volunteers, the building enclosure was able to achieve the required air-tightness score of less than .6ACH @ 50 Pascals.