A passive house is designed to have minimal energy requirements for space heating and cooling and have excellent indoor air quality making it extremely comfortable to live in.
Passive House is a fabric first building approach. Super insulated and air tight requiring only a minimal amount of heating, with most of the heat provided by solar gain and incidental gains from showering, cooking and appliances.
A passive house not only has lots of insulation, but careful detailing to eliminate thermal bridging that allows heat to transfer directly through building junctions or gaps in insulation. A passive house must also achieve a very strict level of air tightness to remove heat loss through draughts. Fresh air is then supplied to individual rooms in the house through a heat exchanger, transfering heat energy from the warm, damp stale air extracted from kitchens and bathrooms.
The Passivhaus standard originated in Germany in 1996 and was developed by the Passivhaus Institut (PHI). Gaining Passivhaus certification is not a requirement to building a low energy home but shows that there has been independent verification that a house meets the passive principals.