Presentation at the 19th International Passivhaus Conference in Leipzig. An overview of some key lessons gained building 3 passivhaus primary schools with the same team. The Architect is Architype who specialise in buildings to the Passivhaus or Passive House Standard. A key lesson was that internal heat gain assumptions have a large impact on design decisions when targeting the passivhaus energy targets. The third school in this series had the lowest cost, highest comfort and lowest energy consumption.