DOE/GO-10097-373 FS 120 ENERGY February 1997 EFFICIENCY AND RCLEARINGHOUSE ENEWABLE Earth-Sheltered Houses ENERGY Let’s assume you’re in the market for a Beginning Your Project, and Cost—will new home. Let’s further assume that, like answer some questions you may have. many other people, you’re concerned Once you’ve decided on an earth- about the limited supplies of domestic oil sheltered house, the sections on Design, and gas, the unpredictable cost, and the Construction Considerations, including loca- environmental price tag attached to the tion, climate, site, and soils, and Construc- continued use of these fuels. tion Materials can help you make the house a reality. Is there any way to reconcile your con- cerns and still build your dream home? Advantages The solution might lie in earth-sheltered There are many advantages to earth- housing. These structures offer many sheltered construction. An earth-sheltered energy-efficient features and are often home is less susceptible to the impact of designed to use solar energy for heating extreme outdoor air temperatures, so you and cooling. Some designs make use of won’t feel the effects of adverse weather recycled materials in their construction. as much as in a conventional house. Tem- peratures inside the house are more stable If you do your homework, earth-sheltered than in conventional homes, and with less construction can be an attractive and temperature variability, interior rooms rewarding choice in housing. The follow- seem more comfortable. ing sections—Advantages, Disadvantages, NREL / PIX02909 This house in Tempe, Arizona, uses earth-sheltered construction methods to help decrease cooling costs. NT O ME F E T N R E A R This document was produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a DOE national laboratory. P G E Y D The document was produced by the Information Services Program, under the DOE Office of Energy Efficiency and Renewable Energy. The Energy Efficiency U A N and Renewable Energy Clearinghouse (EREC) is operated by NCI Information Systems, Inc., for NREL / DOE. The statements contained herein are based on C I I T R E information known to EREC and NREL at the time of printing. No recommendation or endorsement of any product or service is implied if mentioned by EREC. D E M S A TAT ES OF Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste Because earth covers part or all of their construction. Securing financing may also exterior, earth-sheltered houses require be easier if you work with those who have less outside maintenance, such as painting firsthand knowledge of earth-sheltered and cleaning gutters. Constructing a construction and its benefits. house that is dug into the earth or sur- rounded by earth builds in some natural Cost soundproofing. Plans for most earth- Comparing cost factors for building an sheltered houses “blend” the building into earth-sheltered house to those for building the landscape more harmoniously than a a conventional house can be like compar- conventional home. Finally, earth-sheltered ing apples and oranges. Costs vary by houses can cost less to insure because their region, depending on the area’s construc- design offers extra protection against high tion activity and cost of materials. Many winds, hailstorms, and natural disasters earth-sheltered houses are built by their such as tornados and hurricanes. owners and are customized in different Disadvantages ways, adding amenities that can dramati- cally increase final costs. As with any type of unusual construction, there are some disadvantages associated However, when you factor costs, remem- with earth-sheltered housing. Principal ber to consider important expenses that downsides are the initial cost of construc- occur over the life of a house, such as exte- Earth-sheltered tion, which may be up to 20% higher, and rior maintenance and utility costs. Greater the level of care required to avoid mois- initial investment can actually mean your houses moderate the ture problems, during both the construc- ongoing costs, such as heating, cooling, tion and the life of the house. It can take and maintenance, will be reduced. Making impact of extreme more diligence to resell an earth-sheltered the best use possible of natural resources home, and buyers may have a few more may be one of an earth-sheltered house’s outdoor temperatures hurdles to clear in the mortgage applica- greatest advantages. Therefore, in compar- tion process. ison to standard houses, while earth shel- so that the interior ters tend to be slightly more expensive to Beginning Your Project build, these higher initial costs may be offset by the lower energy costs after com- remains at a You may want to start your project by con- pletion. And while energy savings have tacting the organizations that can help you been documented by families living in relatively constant locate architects, builders, and contractors earth shelters, attributing that savings with earth-sheltered building experience solely to the earth-sheltered design would temperature. (a few are listed in the Source List). The be difficult, because most earth-shelters experienced builders in your location can incorporate a wide variety of energy- also ensure that construction plans meet efficient features. area building code requirements, which can depend on a local official’s interpreta- Design tion. Earth-sheltered designs can present some potential difficulty, such as confor- There are two basic types of earth-sheltered mance to minimum window sizes in each housing—underground and “bermed” (or room prescribed by fire codes or building banked with earth). Certain characteristics codes. Other problematic areas are roofing such as the location and soils of your site, specifications and insulation requirements the regional climate, and design prefer- specified by codes; earth may or may not ences are central to which type will work be considered an acceptable substitute for best for you. materials specified. Builders can inform you of the local guidelines, and may also provide cost comparisons between earth- sheltered housing and conventional hous- ing in your area. Using experienced professionals will reduce your personal time investment in researching details of earth-sheltered 2 Since at least part of Underground housing means an entire walls that give exposure to daylight. This structure built below grade or completely design uses a subgrade open area as the the earth-sheltered underground. A bermed structure may entry and focal point of the house. It is be above grade or partially below grade, built completely below ground on a flat house is covered with with outside earth surrounding one or site, and the major living spaces surround more walls. Both types usually have earth- a central outdoor courtyard. The windows earth, it usually covered roofs, and some of the roofs and glass doors that are on the exposed may have a vegetation cover to reduce walls facing the atrium provide light, solar requires less exterior erosion. heat, outside views, and access via a stair- way from the ground level. Atrium/court- maintenance such as From these two basic types, three general yard homes are usually covered with less designs have been developed. They are the: than 3 feet (0.9 meters) of earth primarily painting and gutter because there is no benefit in energy effi- • atrium (or courtyard) plan—an under- ciency from greater depths. This style also cleaning than does a ground structure where an atrium offers the potential for natural ventilation. serves as the focus of the house and the conventional home. entry into the dwelling; The atrium design is hardly visible from • elevational plan, a bermed structure that ground level and barely interrupts the may have a glass south-facing entry; landscape. It also provides good protec- and the tion from winter winds and offers a pri- • penetrational plan, which is built above vate outdoor space. This design is ideal for or partially above grade and is bermed an area without scenic exterior views, in to shelter the exterior walls that are not dense developments, and on sites in noisy facing south. areas. Passive solar gain—heat obtained through windows—might be more lim- An earth-covered dwelling may have as ited, due to the window position in an little as 6 to 8 inches (0.2 meters) of sod or atrium plan. Courtyard drainage and as much as 9 feet (2.7 meters) of earth cov- snow removal are important items to con- ering the structure. An atrium design sider in design. offers an open feeling because it has four Barely visible above ground, the atrium design provides good protection from weather extremes. 3 Usually set into the side of a hill, the elevational design exposes one face of the house and covers the other sides—and perhaps the roof—with earth. The elevational and penetrational plans usually built at ground level, and earth is are more conventional earth-sheltered built up (or bermed) around and on top of housing designs. Elevational plans expose it. This design allows cross-ventilation one whole face of the house and cover the opportunities and access to natural light other sides—and perhaps the roof—with from more than one side of the house. earth. The covered sides protect and insu- late the house. The exposed front of the Construction Considerations house, usually facing south, allows the The climate in your geographical area will sun to light and heat the interior. The floor determine whether an earth-sheltered plan is arranged so common areas and Using designers and house can be a practical housing solution. bedrooms share light and heat from the Studies show that earth-sheltered houses southern exposure.