Five Elements of Passive Solar Design

A strictly passive solar design uses no mechanical elements to distribute heat.Buena Vista Images/Photodisc/Getty Images

A passive solar design is one that relies solely on the strategic placement of windows, walls and floors to absorb and distribute heat from sunlight. The savings in heating bills resulting from a well-planned passive solar design can be significant, and the absence of mechanical features -- such as fans and pumps -- make passive solar designs inexpensive as well. The five interconnected elements of passive solar designs are more about planning and positioning than costly devices.

Aperture or Collector

An aperture is the space through which light passes. The aperture (collector) in a complete passive solar design is the glass window area through which sunlight enters interior space. According to the U.S. Department of Energy, the apertures in a passive solar design should face within 30 degrees of true south. The Department of Energy also recommends installing apertures so that they are unshaded by surrounding trees and buildings between 9 a.m. and 3 p.m.

The absorber in a passive solar design is the hard, darkened surface that absorbs the heat of entering sunlight. This surface can be a wall, floor or partition. The darker the surface of the absorber surface, the more sunlight that is absorbed. Black is considered to be the most sunlight-absorbing color in the color spectrum.

Thermal mass is the material underneath or behind the absorber surface. The absorber surface and the thermal mass of a passive solar design are usually part of the same wall, floor or partition. While the absorber brings the sunlight into its' surface, the thermal mass retains and stores it for longer periods of time.

The distribution element of a passive solar design is exactly what it sounds like: It is the method by which absorbed and retained solar heat is distributed from the absorber and thermal mass areas to various areas of the interior. A true, non-mechanical passive solar design utilizes the natural heat transfer methods of conduction, convection and radiation to distribute absorbed and stored solar heat. Solar heat designs that are not solely passive may incorporate mechanical elements, such as fans and blowers, to further distribute solar heat.

Control in a passive solar design is used to regulate any underheating or overheating that can occur. Control elements can take the form of roof overhang shading, vents, blinds, awnings or fans connected to differential thermostats that turn on when a specified interior temperature is reached.