Editing Passive solar building design (section)

====Roof Pond System====

A '''''roof pond'' ''passive solar system''''', sometimes called a '''''solar roof''''', uses water stored on the roof to temper hot and cold internal temperatures, usually in desert environments. It typically is constructed of containers holding 6 to 12 in (150 to 300&nbsp;mm) of water on a flat roof. Water is stored in large plastic bags or fiberglass containers to maximize radiant emissions and minimize evaporation. It can be left unglazed or can be covered by glazing. Solar radiation heats the water, which acts as a thermal storage medium. At night or during cloudy weather, the containers can be covered with insulating panels. The indoor space below the roof pond is heated by thermal energy emitted by the roof pond storage above. These systems require good drainage systems, movable insulation, and an enhanced structural system to support a 35 to 70&nbsp;lb/ft<sup>2</sup> (1.7 to 3.3&nbsp;kN/m<sup>2</sup>) dead load.

With the angles of incidence of sunlight during the day, roof ponds are only effective for heating at lower and mid-latitudes, in hot to temperate climates. Roof pond systems perform better for cooling in hot, low humidity climates. Not many solar roofs have been built, and there is limited information on the design, cost, performance, and construction details of thermal storage roofs.{{Sfn|Wujek|2010}}