Passive house is a well-insulated building that needs no heating or cooling systems and the term came from German word passivhaus where the haus means any building that can be a school or office, etc. This kind of enclosure reduces the energy consumption by a huge amount and it is widespread in Europe where the energy prices are higher than in US. These building are heated by passive solar gain that generated from the greenhouse effect usually called a sun room which it is more like a double skin façade. Also, the heat from the people and electrical equipment consider a source of heat in this case since the heat transfer from inside to outside is in its minimal values. In some cases, a heating source is needed and usually it is very small. In summer the heat gain is avoided by the efficient design, building orientation and windows location also by using shading elements. High performance enclosure, triple glazed, double skin façade, avoiding thermal bridges and ultra thick layers of efficient insulation make an unusual reduction in energy consumption.
For decades few passive houses were built in the US comparing with Europe, In McKeesport, Pa., a YMCA existing building is converted to a passive house. Pennsylvania got the first certification from the Germany based international passive house institute.
Some critics for this building type is high cost of the material used compared with the payback amount. Also, it may face some problems with the unstable climates and there is still a need for an energy source no matter how the enclosure is sealed then it should be called the net zero energy homes.