A passive building is designed and built in accordance with these five building-science principles: Employs continuous insulation throughout its entire envelope without any thermal bridging. The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air. Employs high-performance windows (double or triple-paned windows depending on climate and building type) and doors - solar gain is managed to exploit the sun's energy for heating purposes in the heating season and to minimize overheating during the cooling season. Uses some form of balanced heat- and moisture-recovery ventilation. Uses a minimal space conditioning system. https://www.phius.org/what-is-passive-building/passive-house-principles