U.S. Department of Energy - Energy Efficiency and
Renewable Energy
Energy Savers
The following five elements constitute a complete
passive solar home design. Each performs a separate
function, but all five must work together for the design
to be successful.
- Aperture (Collector)
- The large glass (window) area through which
sunlight enters the building. Typically, the
aperture(s) should face within 30 degrees of true
south and should not be shaded by other buildings or
trees from 9 a.m. to 3 p.m. each day during the
heating season.
- Absorber
- The hard, darkened surface of the storage
element. This surface—which could be that of a
masonry wall, floor, or partition (phase change
material), or that of a water container—sits in the
direct path of sunlight. Sunlight hits the surface
and is absorbed as heat.
- Thermal mass
- The materials that retain or store the heat
produced by sunlight. The difference between the
absorber and thermal mass, although they often form
the same wall or floor, is that the absorber is an
exposed surface whereas thermal mass is the material
below or behind that surface.
- Distribution
- The method by which solar heat circulates from
the collection and storage points to different areas
of the house. A strictly passive design will use the
three natural heat transfer modes—conduction,
convection, and radiation—exclusively. In some
applications, however, fans, ducts, and blowers may
help with the distribution of heat through the
house.
- Control
-
Roof overhangs can be used to shade the aperture
area during summer months. Other elements that
control under- and/or overheating include electronic
sensing devices, such as a differential thermostat
that signals a fan to turn on; operable vents and
dampers that allow or restrict heat flow;
low-emissivity blinds; and
awnings.
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