A passive system is a non-mechanical heating and cooling system. A passive heatingsystem will use building components - windows, walls, and floors - to capture,store and distribute the energy gained from various natural processes. The energy required to achieve heating or cooling in passive systems is also obtained from natural means. It is not produced or converted using the common active elemts. In passive systems there are no mechanical  collectors to convert natural energy into heat nor pumps or fans to distribute the heat. The energy is used directly. A passive cooling system will use the building components, such as roof overhangs, awnings and window insulated curtains to impede the heat gain during the summer.