Tuesday, February 12, 2013

Low-tech Magazine: The solar envelope: how to heat and cool cities without fossil fuels

Low-tech Magazine: The solar envelope: how to heat and cool cities without fossil fuels


Great article that contains great info on ancient Greek and Pueblo solar housing, here is some;
Solar oriented cities in Antiquity
Knowles' research draws on ancient knowledge, most notably the solar planned cities in Ancient Greece and the solar communities of the Ancient Pueblo People in what is today the Southwestern United States. The Ancient Greeks built entire cities which were optimal for solar exposure. 
Passive solar house in priene greeceOlynthus street planIn the fifth century BC, for example, a neighbourhood for about 2500 people was built in the city of Olynthus. The streets were built perpendicular to each other, running long in the east-west direction (the horizontal streets shown in the plan), so that all houses (five on each side of the street) could be built with southern exposure.
A gridirion street plan oriented at the cardinal points was not new at the time, and neither is it proof of a design aimed at maximum solar exposure. But the Greeks did more. In "A Golden Thread: 2500 Years of Solar Architecture and Technology", Ken Butti and John Perlin note that all houses were consistently built around a south-facing courtyard: 
"The houses that faced south on the street and south to the sun were entered through the court, straight from the street. The houses that faced north to the street and south to the sun were entered through a passageway that led from the street through the main body of the house and into the court, from which access was gained to all other spaces." 
Priene solar oriented cityIn keeping with the democratic ethos of the period, the height of buildings was strictly limited so that each courtyard received an equal amount of sunshine:
"In winter, rays from the sun traveling low across the southern sky streamed across the south-facing courts, throgh the portico, and into the house - heating the main rooms. The north walls were made of adobe bricks one and a half feet thick, which kept out the cold north winds of winter."
Another obvious example of Ancient Greek solar planning was Priene (illustration above), rebuilt in 350 BC and located in present-day Turkey. The city had about 4000 inhabitants living in 400 houses. Its buildings and street plan were similar to those in Olynthus, but because the city was built on the slope of a steep mountain, many of the fifteen secondary streets (running north-south) were actually stairways. The seven main avenues were terraced on an east-west axis.
Native Americans
The Ancient Pueblo People or "Anasazi" built a number of sophisticated solar oriented communities during the 11th and 12th centuries AD in what is now the Southwestern United States: Long House at Mesa Verde, Pueblo Bonito in Northern Mexico and the "sky city" of Acoma.
Drawing by Gary S. Shigemura in Energy and Form by Ralph L. KnowlesIllustration of Acoma Pueblo, by Gary S. Shigemura (from "Energy and Form", Ralph Knowles).
These communities followed a different building style than that of the Greeks. The Ancient Pueblo People constructed terraced buildings of up to three floors high. These were buildings that would fit perfectly in a solar envelope with slanting lines. Acoma pueblo (illustration above) is one example of these orderly, solar planned communities. It consists of three rows of houses built along streets running east and west, so that each building faces south. The streets that separate the houses have a width that allows winter shadows to cover the whole of the adjoining street, stopping just before the following row of buildings. 
Solar houses 2Heliodon
Knowles' research combines the best elements of these historical designs and incorporates modern technology that greatly facilitates the generation of a solar envelope. The heliodon, invented in the 1930s, is a contraption that creates a geometrical relationship between an architectural scale model and (a representation of) the sun. More recently, software versions of the heliodon have made the technology much more affordable, while allowing for the fast generation of even very complex solar envelopes.
On larger sites in particular, and when already existing buildings complicate the generation of a solar envelope, the available computer software saves time and can result in more building volume.

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