Passive building is an integrated building design and construction concept (methodology) that employs basic building science fundamentals to attain high levels of energy efficiency, comfort, durability, and health—in a passive way.
Passive building (passive house) is not a brand name, but a tried and true construction concept that can be applied by anyone, anywhere and to any building type, any construction type (new, renovation, alteration, etc.)
Passive buildings are predominantly heated by “passive” means, such as solar, or internal heat gains, versus a “conventional” building, which is typically heated by large, “active” mechanical systems.
A passive house is a building in which a comfortable internal temperature can be maintained without the use of an active heating or cooling systems. The building is designed to heat and cool itself, hence the term “passive”.
Instead of designing a costly mechanical system to meet the needs of a poor performing building, a passive house is allotted a certain amount of yearly energy demand and peak power loads, and the shell of the building is designed to meet those requirements. After conservation and efficiency are maxed out, then resorting to solar panels is the next best step, not the other way around.