Living within earth shelters has been practiced for nearly as long as humans have been building dwellings, beginning with the utilization of caves.
Today, earth sheltering is the architectural practice of using earth, either via the natural topography or by placing fill against portions of a building’s exterior wall. Earth sheltering naturally insulates the building from large temperature swings, as soil maintains a fairly constant temperature throughout the year. Along with other benefits such as reduced infiltration and greatly reduced building maintenance costs, earth sheltering used in conjunction with passive solar design is a natural and cost effective way to dramatically reduce heating and cooling costs.
While passive solar buildings can be constructed without earth sheltering, the two concepts are so complementary it is hard to imagine one without the other, and earth sheltering remains a hallmark feature of Design Northwest’s passive solar building architecture.
Stable Earth Temperature
The addition of earth sheltering to the building design further enhances the structure’s solar operation. Because the temperature of the ground below the frost line is slow to change and remains relatively constant year round, the surrounding earth creates a blanket of stable temperature around the building. In the winter heating season, the temperature of the surrounding earth is invariably warmer than the outside air temperature. Thus, the building’s heating system has a smaller temperature differential to overcome to maintain a comfortable temperature for the occupants. In the summer cooling season, the temperature of the surrounding earth is cooler than the outside air temperature, and the building remains comfortable with no or minimal use of air conditioning.
Reduced Infiltration
Earth sheltering also protects the structure from prevailing winter winds, further decreasing exterior surface heat loss in the winter. Because the earth largely protects the exterior walls of the building, very little wall surface area is exposed to the outside air. This mitigates warm air escaping and helps prevent unwanted air infiltration, which can be a major heat loss factor in a standard wood frame building. Only when the door is left open do occupants of an earth sheltered dwelling experience the unwanted sensation of a chilly draft.
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