For their home in Potter Valley, California, the Grasso-Underwood family wanted a residence that would suit its rural setting and cool and heat itself naturally. Rammed-earth construction—an ancient building technique now enjoying a renaissance—was the perfect solution: the walls absorb excess heat in the summer, store needed heat in the winter, and blend almost invisibly into their surroundings.
Rammed-earth walls are created by tamping moistened earth into plywood forms. The resulting walls are 18 to 24 inches of solid earth, with a timeless appearance that look-alike styles of new residential construction can't equal. The walls require no paint or maintenance, and last hundreds of years.
In the design of the house, we integrated passive heating and cooling strategies to work with the rammed-earth walls. On winter days, the sun's low arc enters through large south-facing windows to heat the house. This heat is stored in the rammed earth walls and radiates back to the interior of the house at night, keeping the building warm at all hours. In the summer, large overhangs block the sun's higher arcing rays. Any excess heat in the house is absorbed by the rammed-earth walls to keep the house cool. At night, this heat is released from the walls to the cool early morning air, which flows through the house by means of natural cross-ventilation. The house stays cool all summer long without air conditioning, even with average daytime temperatures of more than 85 degrees and highs that regularly exceed 100 degrees.
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