Roof ponds sound may sound murky, but rest assured. They are actually quite tidy, dark-colored water beds placed on the roof. The dark color helps attract solar heat, which the roof ponds store throughout the day. At night, they radiate the heat back into the home through convection.
Roof ponds fall under the category of passive solar heating because they don’t require the use of pumps or other mechanical devices. They usually contain six to twelve inches of water, stored in large plastic or fiberglass containers covered by glazing. The interior space located directly below the installation is warmed by radiant heat.
Solar roof ponds must be used on flat roofs. To maintain their heat, the ponds must be covered at night and uncovered in the morning. Other light maintenance issues include a proper drainage system and adequate support for up to 65 pounds per square foot of dead load. Working with a qualified solar contractor will help ensure your roof pond runs safely and efficiently.
In addition to heating, solar roof ponds are effective cooling tools. When the insulating panels are closed during the day to block out solar heat and uncovered at night to receive cool air, the pond acts as a sort of thermal sponge, collecting the heat that travels up to the ceiling. Whereas heating is done through convection, cooling occurs via evaporation.
Solar roof ponds work best for cooling in low humidity climates but can be modified to work in high humidity climates, too. Solar roof pond heating is especially effective in the southern U.S. The ponds should be unobstructed overhead to gain maximum sun exposure. They are limited to heating single story homes or the upper story of buildings.
Links: