"Another type of building is emerging: one that actually heals the scars of its own construction. It conserves rainwater and fuel and it provides a habitat for creatures other than the human one. Maybe it will catch on, maybe it won’t. We’ll see." - Malcolm Wells, 2002.
The earth sheltered house uses the ground as insulating blanket which effectively protects it from temperature extremes, wind, rain and extreme weather events. An earth sheltered home is energy-efficient, quiet, freeze-proof and low maintenance. Aesthetically an earth sheltered home blends in with the natural environment, leaving more yard space and more space for wildlife.
Fifteen feet below ground the soil maintains a fairly constant temperature equal to the annual average temperature of the area’s surface air. If the average temperature in your area is 55, that means the soil temperature at 15 feet is 55 degrees and in the winter you will only have to bring the temperature inside your earth sheltered home up thirteen degrees, to bring it up to a comfortable 68 degrees. Versus bringing up the inside temperature 68 degrees, if your home is above ground and the outside windchill is 0. In the summer, that 55 degree soil will also keep your home much cooler than an above ground home. Many earth homes incorporate passive solar designs lessening even further the need for fuel for heating or cooling.
There are two types of earth sheltered building. Earth Sheltered - where dirt covers three exterior sides and the roof (the walls are most often concrete). And Earth Bermed - where dirt is pushed up against the exterior walls only, and not onto the roof, yet the roof is usually super insulated.