What Are Passive Solar Houses?

Passive Design

• A successfully designed passive solar house fulfills two functions. It collects, stores and distributes heat from the sun in the winter to keep the living space warm, while at the same time incorporating features that keep it cool in the summer. Geographical orientation, room placement, windows, and insulation are all important design considerations, as are the thermal and convective properties of the walls and roof. Because temperature control in a passive solar house is so dependent on air movement, it must be more effectively sealed than a regular house.

Solar Gain

• A passive solar house can utilize the sun's energy in one of three ways. In direct gain, the house receives the sun's energy through a window or other aperture, stores it in the floor and walls, and radiates it into the living space to heat it. In indirect gain, the sun's energy heats a thermal mass, such as a masonry wall or water tank, and the stored energy radiates into the house by convection. A third method is isolated gain, whereby a single room, called a sunspace, receives energy that can then be transmitted throughout the house by natural or forced convection.

Elements of Passive Design

• Every passive design includes five basic elements. The first is the aperture through which sunlight enters, typically a large window facing in the direction of the sun. The second is the absorber, which is often a masonry wall, sometimes painted black on the outside to increase heat absorbency. The third is a thermal mass to store the heat, which may or may not be the absorber itself. The fourth is a method of distributing the heat throughout the house, and the fifth is a control to allow cooling in the summer months. Typical controls include blinds, roof overhangs and awnings.

Benefits

• Reduced energy costs is one of the main benefits of a passive solar house, but its placement to maximize solar exposure also makes it a pleasant place to live. The quality of life is enhanced by the lack of mechanical devices normally needed for heating and cooling and the resulting reduction in noise levels. Passive solar houses require little maintenance and maintain their value longer than ordinary houses. They frequently have open floor plans to maximize heat transfer, which makes them spacious, and the large windows that let in the sun often afford expansive views.