Some underground buildings are stereotypical bunkers designed to protect people, computer systems and data, and physical objects such as paper documents, photographs, and films. Most underground buildings, however, are attractive, comfortable structures that serve many different functions. More than 500 nonresidential examples in the United States include schools (from preschool to university levels), offices, factories, warehouses, stores, libraries, performing arts theaters, museums, convention centers, and athletic facilities.
Economy is one of the primary reasons for placing all or part of a building below ground. Because of the mass of surrounding earth, these buildings typically use 50–80 percent less energy for heating and cooling. As a result, they require smaller, less expensive heating and cooling equipment.
Another benefit of underground buildings is that they can be nearly invisible. This makes them particularly attractive as visitor centers and museums at historic properties. One notable example is the education center and museum built in 2007 at George Washington’s Mount Vernon estate. Others include the US Capitol Visitor Center (2008) and the Museum of Westward Expansion under the Gateway Arch in St. Louis (1976).
Additions to architecturally notable structures can also be tucked out of sight, under the original buildings or below adjacent lawns. The 2006 addition to the Griffith Park Observatory in Los Angeles is one prominent example. The legislative office complex added to the Texas State Capitol in 1993 is another.
Land conservation is also a significant benefit, particularly in dense urban environments. Underground buildings can be placed closer to property lines and neighboring structures than would be allowable for aboveground buildings. Diminishing the surface footprint of a building creates or preserves open space, provides habitat for local animals, enhances the visual environment, and lets rain fall directly on the living earth.
Far from being depressing warrens, well-designed underground buildings are filled with natural light and fresh air. In addition, recessed courtyards, interior atriums, and skylights provide attractive views for occupants of the buildings. Often, earth-integrated structures are built into the side of a hill, with at least one wall exposed at ground level.
Depending on the local geology, the construction cost of an underground building can be competitive with that of an aboveground alternative. Even when construction is more expensive, other economies can be achieved. Aside from relatively small visible features such as skylights and entry facades, the perimeter walls of underground buildings do not need attractive exterior finishes. More importantly, long-term costs such as energy consumption and repair of weathered or vandalized surfaces can generate significant savings over the lifetime of the building. Insurance premiums may also be less because of the lower potential for damage from storms and fires.
Underground placement sometimes offers a practical solution to a vexing problem. For example, elementary schools located under the flight paths for the Los Angeles and Phoenix airports have quiet classrooms because of earth sheltering. Precision instrument factories located inside bedrock can function without traffic-induced vibration or expansion/contraction of materials due to fluctuating temperatures.
Surprisingly, experience in Japan and San Francisco has shown that underground buildings are remarkably safe in earthquakes. Emergency plans designate San Francisco’s subterranean Moscone Convention Center as an official mass shelter and care facility as well as an alternate site for the mayor's office and the Red Cross Emergency Operations Center.