EARTH-SHELTERED HOUSING: FIRE PROTECTION CONSIDERATIONS
FIRE PROTECTION
Described as “a concrete solution to energy and ecology problems,” earthsheltered or underground housing is gaining in popularity throughout the United States, opening up new avenues in freeform design — and presenting one of the newest challenges to the fire service today.
Earth-sheltered houses generally are built into the side of a hill, with one side of the building exposed. To make these structures watertight and airtight, steel-reinforced concrete is used, approximately 8-12 inches for the roof and 6-8 inches for the walls. To further enhance waterproofing and insulation, some designers apply a waterproofing compound over the entire exterior, as well as a urethane foam and a polyethylene sheet.
Houses must be built at least 10 feet deep to take advantage of the constant temperature afforded by the earth. The more soil surrounding the structure, the less the dwelling is affected by seasonal temperature changes. However 2 feet of soil imposes a weight load of 200 pounds per square foot, said L.L. Boyer, professor of architecture at Oklahoma State University. According to a report in “Concrete Construction,” there are documented collapses of earth-sheltered buildings with concrete block walls and prestressed roof decks.
The attraction of earth-sheltered housing lies in its offering reduced energy costs, tornado and storm protection, privacy and insulation from surrounding noises and vibrations, and improved security from vandalism and the effects of war and nuclear accidents. Some insurance firms also offer lower rates due to these structures being termite proof, rot free, and fire-resistant because of concrete construction.
But fire-resistant doesn’t mean fire free; and the danger of entrapment is all too evident in these subterranean structures, particularly if an escape hatch or skylight has not been incorporated in the design.
Clearly, the difficulties in fighting fires in these structures are due to the airtight concrete construction. In attacking a fire in this type of structure, ventilation is the most important aspect. This airtight concrete shell, with very limited access, allows for tremendous heat buildup from burning synthetic materials such as floor and wall coverings, furniture, appliances, etc.
Ventilation must be utilized for entry. However, unless a skylight or escape opening is present, vertical ventilation methods are next to impossible. In this event, the following procedures should be followed:
- With complete protective clothing including SCBA, fire fighters lay 1 ½-inch lines at the point of entry and ventilation.
- A ventilation hole can then be made by breaching the wall at the highest point possible, or by breaking the top portions of available windows. A 95-gpm fog nozzle will help protect personnel performing this operation.
- Caution cannot be overemphasized, particularly if the fire has advanced to the stage (where the oxygen has been used up) at which a backdraft condition exists.
As with any structure, the best way to fight this type of fire is with prevention, preplanning, and education.
“Most of the subterranean residences in this country are designed by the owner,” said Alan Brunken, associate professor at Oklahoma State University’s School of Architecture, in a report by Charles W. Orton. “The problem is that the owner seldom has any conception of life safety.” People often put the bedroom at the back, away from the exposed wall, which means that the bedroom door is the only possible exit in the event of a fire.
If the house design doesn’t permit the bedroom to be located at an exposed wall, fire fighters should suggest that easilyopened skylights with escape ladders be installed. Also, the public should be informed of basic life safety and fire protection considerations, two easy exits from every room and the installation of heat and smoke detectors, portable fire extinguishers, and residential automatic sprinklers.
Education programs should also be aimed at architects, engineers, and builders, encouraging them to make provisions for rescue access and smoke venting.
Brunken cites the lack of building codes as one of the reasons for poor life safety of earth-sheltered homes. “Most of (these structures) are built in the country where there are no codes. . . This, along with most people’s ignorance of life safety, means that almost all subterranean houses now being lived in have no life safety. About 99 percent.”
—photos by Mark Barga
This problem should be brought to the attention of local governing bodies, and state legislatures should be approached with requests that at least minimum life and fire safety ordinances or codes be enacted.
Finally, fire departments should investigate the number and locations of earthsheltered buildings in their areas and carry out inspections for pre-fire planning.
