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.
The passive approach is to concentrate on the fabric of the building, producing a super insulated and air tight building that will require only a minimal amount of heating, with most of the heat provided by solar gain through careful placement of windows and shading.
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 Passivehaus standard originated in Germany in 1996 and was developed by the Passivehaus Institut (PHI). Gaining Passivehaus certification shows that there has been independent verification that a house meets the passive principals.
Will my house be Passive?
I am intending to design and build a house with passive house principals but not necessarily a certified Passivehaus. Gaining certification normally has additional administrative costs and restrictions that may not actually contribute significantly towards the efficiency and running costs of the house. It is possible to model the house with Passive house software (PHPP) to calculate if it could gain certification and then measure the air tightness of the as built house to see if it is to standard.