Simulated hygrothermal performance of a Passivhaus in a mixed humid climate under dynamic load

• Passivhaus energy use specifications can be met in a mixed-humid climate.
• Traditional heat pump and controls result in many high humidity events.
• Mold growth is unlikely based on relative humidity observed in the simulation.
• Low winter time humidity is also a major concern.

This paper details the dynamic simulation of a small, super insulated Passivhaus residential structure, namely The Ohio State University's entry into the 2011 Solar Decathlon competition. This study explores the use of a conventional vapor compression conditioning system as well as the effects of occupant behavior on the parameters affecting comfort within the structure. It adds to the current literature on the subject by presenting a simulation of a Passivhaus and its HVAC system in a mixed climate where cooling and dehumidification are traditionally required. Furthermore it adopts a simulation tool which acts on time scales significantly less than 1 h. It is concluded that the house, while energy efficient, has difficultly controlling moisture levels. In the summer season it is too humid, and in the winter it is too dry. The study concludes that conventional HVAC equipment cannot fully address the moisture and indoor air quality issues that are a result of new building techniques with stringent air infiltration and insulation standards.