Editing Passive solar building design (section)

==Passive energy gain==
''Passive solar'' technologies use [[solar energy|sunlight]] without active mechanical systems (as contrasted to ''active solar'', which uses [[solar thermal collector|thermal collectors]]). Such technologies convert sunlight into usable heat (in water, air, and thermal mass), cause air-movement for [[ventilating]], or future use, with little use of other energy sources. A common example is a [[sunroom#Solarium|solarium]] on the [[equator]]-side of a building. [[Passive cooling]] is the use of similar design principles to reduce summer cooling requirements.

Some passive systems use a small amount of conventional energy to control dampers, shutters, night insulation, and other devices that enhance solar energy collection, storage, and use, and reduce undesirable [[heat transfer]].

Passive solar technologies include direct and indirect [[solar gain]] for space heating, [[solar water heating]] systems based on the [[thermosiphon]], use of [[thermal mass]] and [[Phase Change Material|phase-change materials]] for slowing indoor air temperature swings, [[solar cooker]]s, the [[solar chimney]] for enhancing natural ventilation, and [[earth sheltering]].

More widely, solar technologies include the [[solar furnace]], but this typically requires some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for widespread use. 'Low-grade' energy needs, such as space and water heating, have proven over time to be better applications for passive use of solar energy.