Earth Sheltered Homes: Comfortable, Affordable and Energy Efficient

Dan Chiras discusses the advantages of earth sheltered homes, includes information on earth sheltered homes that are comfortable, affordable and energy efficient.


| February/March 2003



The soil bermed around this home in Tempe, Arizona, helps the house keep its cool.

The soil bermed around this home in Tempe, Arizona, helps the house keep its cool.


PAMM MCFADDEN

Learn about the advantages of living in earth sheltered homes.

Earth sheltered homes fit a wide range of climates and a variety of building sites — even flat ones. Paired with passive-solar design, an earth sheltered home can save you tens of thousands of dollars in fuel bills during your lifetime.

Earth sheltered homes are comfortable, affordable and energy efficient. And, if thoughtfully designed, earth sheltered homes admit an abundance of natural light and are far less of an imposition on the landscape than conventional aboveground houses.

Subterranean Secrets

Earth sheltered homes provide year-round comfort, but not because earth is a good insulator. It's not. Soil has an insulation value of about 0.25 per inch: 14 times less than wet-blown cellulose insulation and 20 times less than certain types of rigid foam insulation.

The secret of earth sheltered homes actually lies in the constancy of the earth's temperature and its thermal mass. Below the frost line (usually 24 to 60 inches below the surface), the soil maintains a fairly constant 50 degrees, plus or minus a little, depending on the location. The baseline temperature in an unheated, earth sheltered home in a cold climate (like mine in Colorado, for instance), hovers around 50 degrees. Besides taking advantage of the soil's temperature-moderating effects, earth sheltered homes also are protected from heat-robbing winter winds and the scorching summer sun. Because conventional aboveground homes expose most of their surface area to the elements, they are more vulnerable to temperature swings, conduction, convection and air infiltration. If outdoor temperatures plummet to 20 degrees below zero, for example, an aboveground home will need a boost of nearly 90 degrees to be comfortable. Raising an earth sheltered home's internal temperature to the same temperature (around 70 degrees) requires only a modest, 20-degree boost, which is easily provided by passive-solar gain from sunlight. The sod's constant temperature, transferred to the home, also means that you never have to worry about water lines freezing.

In summer, earth sheltered homes use the sod to keep their cool. It may be a blistering 95 degrees outside, but earth sheltered homes stay in the low 70s — as cool as any air-conditioned home — without use of a noisy, energy-guzzling air conditioner and without astronomical utility bills.





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