Date: Oct 08, 2013 Source: (
click here to go to the source)
THERE was a time, long before Home Depot and cement mixers, when people had to build their homes from nearby materials. Centuries ago, the Indians of the Southwest used a mix of sand, clay, straw and water to make adobe homes. The Chinese constructed houses out of bamboo, and the English used a combination of straw and moist earth known as cob.
Enlarge This Image
Eric Draper for The New York Times
Rick Torcasso's home has many automated features.
The old ways never died out entirely, but they fell into disuse as new manufacturing techniques led to houses made with two-by-fours, concrete and steel. Now a form of construction known as "natural building" has attracted followers, as people realize that some housing traditions may be worth reprising — in large part because of the energy savings they can yield.
Homes built with natural materials like straw, sand, earth and rock conserve energy in two ways: Using them cuts down on the pollution that results from producing and transporting manufactured materials, and once the homes are built they can significantly reduce energy costs and consumption.
There are drawbacks: labor costs can be high and concerns raised by city officials and inspectors have the potential to hinder construction. But two processes — using straw bales and rammed earth, a material similar to adobe — are making inroads.
Catherine Wanek, co-author of "The Art of Natural Building: Design, Construction, Resources" and a straw bale proponent, said that even though most naturally built homes have electricity and other modern comforts, they can still be designed "to capture the winter sun when we need it and keep out the summer sun when we don't want it."
Straw has been mixed with earth to build houses since the beginning of human habitation, she said, and in the 19th century the invention of the baling machine vastly sped up construction.
Using straw bales in modern homes is inexpensive because it is a byproduct of grain crops like wheat, rye, oats, barley and rice. The straw must be fully encased in plaster, often made of lime or clay, to protect it from insects, rodents, wind, fire and especially moisture.
Once the house is built, the hollowness of the individual stalks traps air in tiny pockets, creating natural insulation. "You can stack those bales like giant bricks to create a super insulating system," said Ms. Wanek, who built a straw bale greenhouse to capture solar energy for the 1880s stone lodge she runs in Kingston, N.M.
The insulation efficiency (the so-called R-value) of straw bale walls is about the same as for fiberglass insulation, Ms. Wanek said. The bales' superior energy performance comes from the fact that they are so thick compared with fiberglass-insulated walls.
As for cost, including labor, building with straw bales can be comparable to a custom-built conventional home, she said. After a straw home is built, and especially with solar energy collection, the energy savings are great, she said. "Roughly we find that you save approximately two-thirds or more of your heating and cooling energy over conventional construction," she said. She estimates that there are between 7,000 and 8,000 straw bale homes in the United States.
Richard Mandelbaum, 43, and his wife, Gabrielle Kahn, 41, built a straw bale home 10 years ago in a wooded area in Forestburgh, N.Y., in southern New York State. They split their time between Forestburgh and a rental apartment in Brooklyn. Their use of electricity and fuel in the 1,100-square-foot Forestburgh house is low, since they don't use air-conditioning, and a wood stove provides heat.
"We knew we wanted to build in a more natural and eco-friendly way, not just because you can make it efficient and save money," but also because it was better for the environment, Mr. Mandelbaum said. The walls are made of New York rye; the plaster is made of clay and sand from the area; and the roof insulation is from recycled cotton. It cost about $130,000 to build the house; the baled rye, from a local dealer, was a little over $1,000.
Mr. Mandelbaum says he enjoys the look and feel of the house, adding that the walls are "rounded and organic." He says the finished product reminds him of adobe, which may be a reason that straw bale is popular in New Mexico.
In New Mexico, adobe bricks have never gone out of style. But efforts to expand adobe construction are hampered by the fact that it can crack during an earthquake. So a cousin of adobe, rammed earth, is slowly gaining adherents in the West and elsewhere.
Rammed earth walls are made of subsoils (which lack the organic content of topsoil) on or near the housing site. To meet building codes, a small percentage of cement must be added to the mix. A hand-held pneumatic tool packs a mix of local subsoils into a temporary wooden form to construct the walls.
Rammed earth has a lower R-value than fiberglass, but it is "tremendous at storing thermal energy," said David Easton, a builder and founder of Rammed Earth Works, based in Napa, Calif. In other words, it takes a long time for the outside temperature to make its way inside. Houses made of rammed earth perform best in climates with a high "diurnal swing" — for example, in New Mexico and California — so that cooler temperatures at night can keep the house comfortable during the day.
The homes can be costly because much of the labor must be done on-site. Mr. Easton, who has built about 300 rammed earth homes, is working on developing smaller blocks of earth that can be transported, which would reduce labor costs considerably, he said.
After Rick Torcasso, the chief executive of a marketing company, decided to build a rammed earth home on a mountain in Santa Fe, N.M., the builders used subsoil from the mountain itself as construction material. The 5,500-square-foot house cost $4 million to build.
Mr. Torcasso, 59, uses a computer to automatically regulate his home's heating and air-conditioning. Last July, a very hot one, the air-conditioner was on only 8 percent of the time, Mr. Torcasso said. His electricity bill was $22 that month, partly because of credits he receives for using solar energy.
Juliet Hsu, a 34-year-old architect, has radiant heat floors but no air-conditioning in the rammed earth house she designed for herself and her husband, Jack Menzel, in Mountain View, Calif. (Mr. Menzel works for Google, which is based there.) The 2,200-square-foot house, where they have lived for two years, cost $500,000 to build; the builder, Mr. Easton, is Mr. Menzel's stepfather.
Mr. Torcasso and Ms. Hsu said that living in a rammed earth home is aesthetically appealing. The striation created by the layers of soil creates "beautiful lines," Ms. Hsu said.
Neither had more than the usual issues with obtaining permits, but in some cases, "contractors don't know how to build that way and code officials have to figure out new rules," said Larry Speck, an architect based in Austin., Tex., and a professor at the University of Texas at Austin.
"Most inspectors are not familiar with the building processes for rammed earth or straw bale homes and have no idea what the inspection concerns are," said Nick Gromicko, founder of the International Association of Certified Home Inspectors.
Professor Speck says he hopes that builders and officials will become more knowledgeable, because "what could be greener than using the material that's sitting right there?" Not only that, he said, but "the actual building materials themselves are contributing to the comfort of the people in the house."
