Because of a super-insulated, high performance “Passive House” design, a central heating system was not required to meet heat load requirements.  The building official allowed a smaller-than-standard heading system, a Navien combi-heater: a high efficiency, tankless, natural gas powered water heater that delivers heated hydronic fluid to a fluid-to-air heat exchanger installed in ductwork for the home’s ventilation system.  Energy efficiency, building science and technology make a house that is extremely airtight and insulated.