The Passive House concept continues to scale up in North America, in both number and size of projects. Passive House buildings benefit from airtight construction, as minimizing winter infiltration directly lowers energy consumed when heating the building. Airtight construction also hinders airborne moisture from escaping through the building skin, thus requiring new thinking about the requirements of the ventilation system. This session examines the causes and solutions to humidity buildup in Passive House buildings and is for those interested in learning how to achieve peak energy performance from their ventilation system while minimizing the risk of excessive moisture buildup.