How do paper houses stack up? (Sustainable Development).

In the tale of the Three Little Pigs, children learn that houses made of heavy brick or wood are preferable to those made of lightweight straw. That axiom is being challenged by the reemergence of a building material known as fibrous cement, or "papercrete." Composed of recycled paper, water, sand, and Portland cement, papercrete makes a strong, light-weight, and inexpensive building material that could replace concrete block and wood used in traditional construction--or could it?

Papercrete is currently enjoying a boom among builders in the Southwest who are looking for low-cost building materials that have minimal impact on the environment. "Paper houses make sense," says Gordon Solberg, author of Building with Papercrete and Paper Adobe. "Our landfills are clogged with waste paper and cardboard. Millions of people live in substandard housing or have no housing at all. With papercrete, we can solve both of these problems at once."

According to the National Association of Home Builders, the average U.S. single-family home contains 13,127 board feet of lumber, 13.97 tons of concrete, and 2,085 square feet of flooring. Trees must be cut down to supply that lumber and energy consumed to manufacture and transport building materials. Much of the material later ends up as land-filled scrap.

Papercrete, on the other hand, uses primarily locally available material and is prepared on-site. Using a customized mixer, dry ingredients are mixed with water to make a slurry that can be molded or dried into stackable blocks. Leftover papercrete can be thrown back into the mixer and ground up to make new material.

Because papercrete is not manufactured commercially, comparative building costs are hard to determine. However, contractors claim figures of less than $2 per square foot of finished wall using papercrete versus $6 and $9 per square foot for wood frame and block construction, respectively.

According to Solberg, papercrete blocks are capable of a compressive strength--the measure of how much weight can be put on the material--of 260 pounds per square inch, compared to approximately 1,800 pounds per square inch for concrete block. Papercrete can also attain an R-value--the measure of how well a material insulates--of approximately 2.0 per inch. Theoretically, a 10-inch-thick papercrete wall would have an R-value of 20.0, superior to a conventional wall made of fiberglass batting, gypsum wallboard, and wood or vinyl siding.

However, Leonard Jones, an engineer from Littleton, Colorado, has done some experiments with papercrete that reveal less desirable qualities. He says the physical characteristics of papercrete vary widely, depending upon the relative amounts of sand and Portland cement used. Mixtures with a lot of sand and cement tend to have a high density and a relatively high tensile strength, but a low R-value--less than 1.0 per inch. Mixtures with less sand or Portland cement tend to have a lower density, a relatively low tensile strength, and a higher R-value--but still generally less than 2.0 per inch. In addition, because papercrete loses most, if not all, of its strength if it gets wet, Leonard says he would not recommend that papercrete be used for any structural components; instead, it should be used as in-fill in a building with an independent metal, pole, or wood frame.

Papercrete is also not necessarily free of health concerns, although it has not been extensively tested. Portland cement contains silica, and respirable crystalline silica, created when cutting or drilling through cement, has been implicated in silicosis-related death and disease among construction workers. In addition, low-density papercrete mixtures could catch fire and burn slowly.

General contractors do not use papercrete, so home builders must either do it themselves or find an "alter native builder." Papercrete has not yet been approved under commonly used building codes such as the International Building Code. Thus, builders generally use it in areas that do not have building codes or that allow experimental permits.

"The challenge this and other alternative building materials face is passing all the testing requirements for code approval," says Alex Wilson, executive editor of Environmental Building News. "It's hard [for alternative materials] to get a foot in the door."