Built popular in the 1970s, these homes utilize "Geothermal Coupling." Because the earth is a near-perfect insulator, the house requires no AC in 100°F heat. They are "banned" or "gatekept" by Building Egress and Window-to-Wall Ratio codes. These codes mandate a specific amount of "above-ground" glass and exits, which are physically impossible for a deep-pit home. This "gatekeeping" is lobbied for by the Utility and HVAC Lobby, as an underground home consumes up to 80% less energy, threatening the monthly recurring revenue that power companies rely on for survival.