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Building Design: Passive Solar

posted 13 Feb 2010, 23:56 by Toby Roscoe   [ updated 14 Feb 2010, 00:08 ]

Passive solar design uses solar access, geometry of the window areas   and thermal mass to maintain interior temperatures at comfortable levels throughout the Sun's daily and annual cycles, with very little input required from active heating and cooling systems. Passive solar design is an intelligent use of natural energy resources that must be incorporated into the planning and development stages of the building project. 

Coupled with the correct insulation and other efficient building materials, such as low-e glass, passive solar massively reduces a building’s dependance upon fossil fuels for heating, cooling and lighting and has consequent reductions in greenhouse gas emission.

Passive solar building design is one part of green building design principles, but does not include active systems such as mechanical ventilation or photovoltaics (solar electric). If a passive solar building is fitted with a renewable energy system, then it is possible for its energy balance to be positive, that is excess energy may be sold back to a utility company and renewable energy certificates (RECs) may be generated.

Passive Solar technologies convert sunlight into usable heat (water, air, thermal mass), cause air-movement for ventilating, or future use, with little use of other energy sources. A common example is a solarium on the equator-side of a building. Passive cooling is the use of the same design principles to reduce summer cooling requirements.

Technologies that use a significant amount of conventional energy to power pumps or fans are active solar technologies. 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, 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 materials for slowing indoor air temperature swings, solar cookers, the solar chimney for enhancing natural ventilation, and earth sheltering. More widely, passive solar technologies include the weiner solar furnace and solar forge, but these typically require some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for wide-spread 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.