casas construidas con sacos de arena

Inside a finished earthbag home

Kelly Hart/Courtesy www.EarthbagBuilding.com

Why build with earthbags?

Earthbag homes are inexpensive, with many builders able to use the soil that's on-site to build the home. Bags are usually low-priced in bulk, particularly misprinted bags that companies sell at reduced rates. But we'll talk more about materials in earthbag construction in the next section. While earthbag structures are labor-intensive, they are relatively easy to build with little experience and a crew of only a few people, cutting down on construction and contracting costs.

Earthbags could be used as infill for a conventionally framed house, but typically they're more monolithic structures, meaning that the entire structure is made from the same materials throughout. Other than the bags and the barbed wire that holds the bags together, earthbag building is a natural building method that eliminates the use of limited resources. For example, an earthbag dome building can eliminate 95 percent of lumber that is currently used to build a stick frame house [source: Hunter and Kiffmeyer].

Earthbag homes also appear to be structurally sound and safe. Architect Nader Khalili conducted structural integrity tests under the supervision of the International Conference of Building Officials. He tested earthbag domes under conditions simulating seismic, wind and snow loads, and the tests surpassed the 1991 Uniform Building Code's rigorous requirements by 200 percent [source: Hunter, Kiffmeyer]. Anecdotal accounts tell of the structures surviving fires, floods and hurricanes. Properly plastering the walls will keep out mold, insects and rodents.

Earthbag walls also exhibit high levels of thermal mass, which is the measure of a material's ability to absorb, store and transfer heat. Earthbag walls that are greater than 12 inches thick (0.3 m) exhibit thethermal flywheel effect. At the hottest time of the day, the walls will absorb the heat, but they don't release it into the structure until the walls start cooling at night. This creates about a 12-hour-delay between the time in which the walls soak in the heat and when they release it. For this reason, earthbag homes work best in locales where there is a significant difference between daytime and nighttime temperatures.

Once an earthbag home is complete, you would never guess that the walls are made of dirt. The walls are strong enough to hang cabinets and pictures, and plumbing and electricity are installed just as in a conventional home. Lofts can provide extra space. Earthbag builders Kaki Hunter and Donald Kiffmeyer speak about the warmth and "spiritual" benefits of living within earthen walls, but others have pointed out that for some, earthbag walls are too heavy and "organic"-looking [source: Kennedy]. We'll talk about other potential disadvantages of earthbag construction later.

Because of the low costs, ease of construction and use of locally available materials, many earthbag builders see this form of construction as an ideal way to provide temporary shelter after natural disasters. Earthbag structures are more durable and sustainable than the sheet tents that are normally distributed to displaced survivors, but they are more expensive. Khalili was frustrated with the red tape that he faced in presenting earthbag's case to the government, and he turned to the Internet as a way to teach people how to build an earthbag home. He posted two pages of easy instructions with lots of pictures on the California Institute of Earth Art and Architecture's Web site that can be printed and taken to the construction site [source: Stevenson, Ferreira].