Passivhaus buildings benefit from very little energy usage for heating and cooling as well as high level of comfort. However, in order to Passivhaus property, there are a few principles need to be followed. First, the space heating and cooling demand should be less than 15kW/m2, and the heating and cooling load should be less than 10W/m2. Second, the overall energy demand should be less than 120kWh/m2/year. Third, the air change rate should be less than 0.6/hour @ 50 Pa. In addition, typically it includes high quality insulation, insulated window frames, airtight building fabric, as well as mechanical ventilation scheme that provides efficient heat recovery.