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re: heat loss through skylight
29 dec 2005
m ransley wrote:
>now you recommend an overhang on peoples roofs to shade summer sun...
yup... 2000-year-old physics :-)
well, maybe 2500 years old...
nick
http://www.californiasolarcenter.org/history_passive.html
during the fifth century bc., the greeks faced severe fuel shortages.
fortunately, an alternative source of energy was available - the sun.
archaeological evidence shows that a standard house plan evolved during the
fifth century so that every house, whether rural or urban, could make
maximum use of the sun's warm rays during winter. those living in ancient
greece confirm what archaeologists have found. aristotle noted, builders
made sure to shelter the north side of the house to keep out the cold winter
winds. and socrates, who lived in a solar-heated house, observed, "in houses
that look toward the south, the sun penetrates the portico in winter" which
keeps the house heated in winter. the great playwright aeschylus went so far
as to assert that only primitives and barbarians "lacked knowledge of houses
turned to face the winter sun, dwelling beneath the ground like swarming
ants in sunless caves."
cross section of a roman heliocaminus. the term means "sun furnace." the
romans used the term to describe their south-facing rooms. they became much
hotter in winter than similarly oriented greek homes because the romans
covered their window spaces with mica or glass while the greeks did not.
clear materials like mica or glass act as solar heat traps: they readily
admit sunlight into a room but hold in the heat that accumulates inside. so
the temperature inside a glazed window would rise well above what was
possible in a greek solar oriented home, making the heliocaminus truly a
"sun furnace" when compared to its greek counterpart.
fuel consumption in ancient rome was even more profligate than in classical
greece. in architecture, the romans remedied the problem in the same fashion
as did the greeks. vitruvius, the preeminent roman architectural writer of
the 1st century bc., advised builders in the italian peninsula, "buildings
should be thoroughly shut in rather than exposed toward the north, and the
main portion should face the warmer south side." varro, a contemporary of
vitruvius, verified that most houses of at least the roman upper class
followed vitruvius' advice, stating, "what men of our day aim at is to have
their winter rooms face the falling sun [southwest]." the romans improved on
greek solar architecture by covering south-facing windows with clear
materials such as mica or glass...
settlers in new england considered the climate when they built their homes.
they often chose "saltbox" houses that faced toward the winter sun and away
from the cold winds of winter. these structures had two south-facing
windowed stories in front where most of the rooms were placed and only one
story at the rear of the building. the long roof sloped steeply down from
the high front to the lower back side, providing protection from the winter
winds. many saltbox houses had a lattice overhang protruding from the south
facade above the doors and windows. deciduous vines growing over the
overhang afford shade in summer but dropped their leaves in winter, allowing
sunlight to pass through and penetrate the house...
george fred keck, a chicago architect... began designing homes in the
chicago area according solar building principles - expansive south facing
glass to trap the winter sun, long overhangs to shade the house in summer,
minimal east-west exposure to prevent overheating in summer and fall, and
the placement of secondary rooms, garages, and storage corridors on the
north side to help insulate the living quarters from the cold north winds.
keck had a knack for publicity and called the houses he designed "solar
homes." by the mid-forties keck's work caught the attention of the national
media. house beautiful, reader's digest and ladies home journal featured his
work. fuel rationing during the war inclined the american public toward
valuing the energy saving features of solar homes. when war ended, the
building market exploded. with the wartime-conservation ethic still imbued
in most people's minds, many manufacturers in the prefabricated home
industry adopted solar design features for leverage in this highly
competitive market.
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