Milena Karanesheva and Mischa Witzmann—the married couple behind Paris-based Karawitz Architecture—designed a 1,733-square-foot house that uses only 4,200 kilowatt-hours per year—about a tenth of what a conventionally constructed house in France might use. With no other means of heating or cooling than those generated by the structure—a tenet of Passive House design—the new home is modeled on the French country dwellings of the area. Photo by Nicholas Calcott.