Solar home heating and cooling technology
has been evolving for thousands of years. Beginning with the
Greeks, it has been passed on from culture to culture down
through the centuries resulting in the high-tech solar home of
today.
Active and Passive Solar Systems
There are two types of solar systems used
to heat and cool houses–passive and active. In the former,
builders construct and landscape the structure, itself, so
that it becomes, in effect, a large solar collector. In a
passive system, there’s only one moving part–the earth
moving around the sun. In the latter, builders use solar
collectors or arrays of solar cells to provide energy in the
form of heat or electricity.
A passive solar building is one designed to
use the entire building–walls, floors, windows, and
roofs--as solar collectors. It uses no mechanical devices,
such as motors, pumps, or fans to distribute heat. A
well-designed building functions in harmony with the local sun
and weather conditions, with spaces and components arranged so
that heat transfer is primarily by natural convection and
radiation. The result is an efficient and liveable building,
with side benefits of increased brightness and more
comfortable surroundings. To make the house even more energy
efficient, it can be partially buried and constructed of thick
adobe. A top tier of windows can heat the rear of the house,
while stone walls behind large windows provide heat for the
front.
An active solar system employs large roof
collectors that permit the sun to heat either air or a working
fluid which is pumped to a storage unit. Heat reservoirs are
usually in basements or crawl spaces because of their large
size and weight. Active houses must still face south, and in
addition to large windows, which are passive collectors, roof
collectors are included.
The Typical Solar House
The typical solar house of today
should have overhangs that shade windows and walls against
high summer sun. In winter, when noonday sun is more than 40'
below the summer zenith, heat filled rays can enter the
structure. This simple architectural adaptation, fully
exploited by the Greeks and Romans, is still an energy saver.
Further, a solar house should have a
light-colored roof to reflect summer heat, double-pane glass
to hold in valuable heat in winter, and windows on the south
and east sides but few or none on the north and west sides. As
sunlight passes through the glass, it strikes various
surfaces. Part of the visible light is reflected back out of
the glass, while heat is trapped inside, causing a greenhouse
effect. Instead of the normal two-by-four studding, wall studs
should be two by six inches to provide for more insulation.
The most important building concept is to
orient the house to a southern exposure to take advantage of
the sun in winter and shade in summer. This applies to both
passive and active houses. However, builders today ignore
proven principles that have existed for thousands of years in
favor of economic considerations. Most modern houses are gas
(or oil) guzzlers. It’s simpler and cheaper in the short run
to continue building the American box than to use innovative
designs that are more energy efficient. And even with the
increased efficiency of today’s insulation, developers are
building most large new houses on tracts of land with few
trees to shield the sun’s rays in summer.
Contrary to popular belief, a solar house
need not be complex or expensive to build. Most solar homes
are hybrids, except in the warmer areas of the sun belt.
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