The Passive House Institute developed EnerPHit certification standards to accommodate the realities of existing old buildings, where foundations, party lines, historic preservation, cost, and other factors make a typical Passive House certification impractical. This course takes a detailed look at the criteria, the pathways, and the potential exemptions, that drive EnerPHit performance to deliver the health, efficiency, and resilience results we expect from Passive House. Through case studies of successful retrofits, see how to upgrade a building with respect to airtightness, insulation, thermal bridge reductions, high-performance windows, and ventilation.