The sun continually radiates upon us two resources: heat and light. Passive solar energy
is the art of deploying what nature has given to attend our desires with minimal effort or external energy input.
Depending upon our immediate needs we might want more or less of either heat or light. The facing and design of buildings can be oriented to maximize these resources when we want them, and minimize them when we don't. "Passive design strategies can dramatically affect building energy performance. These measures include building shape and orientation, passive solar design, and the use of natural lighting."22 For instance, during the winter we often wish to maximize both heat and light, while in the summer we may want to maximize light while minimizing heat. Overall, according to one solar architect, "compared to a conventionally designed house of the same square footage, a well-designed passive solar house can reduce energy bills by 75% with an added construction cost of only 5-10%."23
In the northern hemisphere, a southern exposure with glass windows will maximize solar heat gain, while in the southern hemisphere the orientation is reversed. Specific climate and environmental features should be taken into account for more specific features. Concrete, brick, or adobe materials within the house (the thermal mass) will absorb and hold heat. Because the sun is higher in the sky during the summer, the building will take in and trap less heat, providing a built-in mechanism to adjust to seasonal change. Various forms of shading can also help prevent overheating during hot periods. Vents that open near the top of a building will also allow hot air to rise and escape when necessary.
An indirect gain strategy to collect and store energy is the
Trombe wall, which uses glass and masonry to absorb radiant heat.24
The addition of vents may help heat to flow inward throughout
the house. In general vents, fans, windows, and shades can be
strategically placed then opened and closed to regulate temperature
Often a building's occupants will want to use natural sunlight while avoiding glare and heat, particularly in the summer. Daylighting is the use of daylight to illuminate interiors, particularly "the diffuse natural light coming from the surrounding sky and reflected sunlight."25 Overhangs, shelving, sloping and other strategies can allow light to be reflected into a building yet "prevent direct solar gain and glare."26
Because daylighting has "more than twice the luminous efficacy (i.e. light output per unit of heat generated) of fluorescent lighting,"27 daylighting can simultaneously save money on light generation and on air conditioning that would be required to counteract the heat generated by electric light. Studies also show that employees are happier and more productive in a naturally lit environment.
Go To Renewable (and reusable) Energy
List of Visuals
- Solar Tube, Vienna, Austria, 2001
© James Morris, photographer, courtesy National Building Museum
Stacked three floors high on a small wooded
lot, the Solar Tube utilizes special glazing that allows warm
sunlight to enter while deflecting damaging UV rays. The house's
central core of reinforced concrete absorbs and stores the sun's
warmth, keeping the temperature of the living spaces within
a comfortable range.
- Passive Solar Heating and Cooling
Sound Home Resource Center (3801 NE 98th Street, Seattle, WA 98115-2534)
- Potential for passive solar heating in the United States
Dennis Holloway, an Architect in Northern New Mexico (625 Ivory Road SE, Rio Rancho, New Mexico)