Earth sheltered construction
Earth sheltered construction, or earth sheltering, is the practice of heaping earth over and/or around a building.
This increases the insulation of the building against extremes of both hot and cold. It is an ancient building technique, but has recently returned to popularity as one aspect of passive solar construction. In its most basic form an earth shelter could be a cave in a hillside, however building design has evolved so that designs now incorporate modern sustainable architecture into an efficient, earth-covered shell.