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"A Simple Design Methodology for Passive Solar Architecture", by Dennis Holloway, Architect (An Architect in Northern New Mexico)
Author's Note: The following information is a precipitation of knowledge acquired through my practice and research in the 1970's regarding the use of solar energy to 'passively' heat and cool buildings. I believe that continuing dissemination of this information through the Internet is very important in a time when earth's bio-environment is so endangered by the continued combustion of fossil fuel into the atmosphere. Please copy this page and distribute it freely.
The ancient discovery that the shadow of a "gnomon"--an arrow stuck vertically into the ground--mirrored the perfectly symmetrical path of the sun across the sky is as important to the development of civilization as the discovery of the wheel. By studying the movements of this shadow people first conceived of the 90o (right) angle--the foundation of geometry, and ultimately of architecture. A result of this "shadow science" origin is that most architecture and city street grids are related to the north-south east-west axes. The ancients also gained great insights into the potential of architecture to modify the sun's shadow and radiant heat.
Indeed, using the sun as a heat source is nothing new. In XENOPHON'S MEMORABILIA, written 2400 years ago, Socrates observed:
"Now in houses with a south aspect, the sun's rays penetrate into the porticos in winter, but in the summer, the path of the sun is right over our heads and above the roof, so that there is shade. If then this is the best arrangement, we should build the south side loftier to get the winter sun and the north side lower to keep out the winter winds. To put it shortly, the house in which the owner can find a pleasant retreat at all seasons and can store his belongings safely is presumably at once the pleasantest and the most beautiful."
While the Greek house that Socrates described probably lost heat as fast as it was collected, due to convective and radiation losses, the Romans discovered that if the south-facing portico and windows were covered with glass, the solar energy would be trapped causing the internal temperature to stay constant into the night. This simple phenomenon called the "greenhouse effect" is illustrated by the experience of returning to your car on a sunny, cool day and finding it overheated. Today we call the house that uses the greenhouse effect for heating a "passive solar house."
It is a common rule-of-thumb that 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%. In many parts of the U.S. passive solar houses do not require any auxiliary energy for heating and cooling. Given current and future projected fuel costs, the additional construction cost is recovered quickly. Official surveys show 100,000 passive solar homes in the U.S. (1984), but informal estimates bring to one million the number of buildings that employ some aspects of passive solar design, often south-facing greenhouses...
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