Straw bales stack up for buildings

Straw bales stack up for buildings

Bainbridge, David A

.A lost art resurface in the modern world

An old construction material is making a comeback as a strong, new alternative for buildings. Straw bale-built structures are emerging throughout the world on farm, commercial and residential property. The traditional building system has been successful in a range of environments from the arid Arizona desert to the cold steppes of Mongolia. In keeping with modern practices, straw bale building codes are also becoming common.

Straw bale construction developed in western Nebraska’s Sand Hills more than 100 years ago. Builders there found the area’s sandy soil a poor mix for making sod blocks. New steam-powered balers – and perhaps straw shelters made by the native people – inspired the builders to try straw bales. Straw bale buildings, dating to 1905, have been found in good condition today.

This U.S. building method has been rediscovered and its use increased during the last 10 years. Straw bales are durable, fire resistant, quiet and two to four times as energy efficient as conventional wall construction. They also offer a way to use waste straw, which is typically burned in the field causing air pollution and health concems.

Ten years ago, a modem-day straw bale building workshop in Oracle, Ariz., helped re-establish the the old method as a promising new alternative. Two basic approaches have emerged: load bearing bale walls; and timber, steel or concrete framed buildings with straw bale fill. One of the most promising approaches combines straw bales with metal framing.

Modern straw bale pioneers are researching and testing designs to inspire a new generation of builders to make the structures practical for large scale developments.

Straw bale construction can improve comfort and enable homeowners and building managers to reduce energy consumption for heating and cooling. Preliminary data from straw bale buildings in Mongolia suggest residential energy use can be reduced 80 percent. The superlative insulation values of the thick walls, ceilings and roofs make them well suited for natural heating and cooling systems in extreme environments.

Many countries, states, counties and cities have approved straw bale buildings and adopted, or are developing, straw bale building codes. Straw bale builders’ associations are also supporting research in this area.

The demand for straw bale homes and commercial buildings will depend on market penetration and building costs. Bale building costs range from $1.50 per square foot (.093 square meter) in Mexico to more than $200 per square foot (.093 square meter) for custom upscale homes in Santa Fe, N.M. Recent research suggests that building costs can be kept to about S30 per square foot (.093 square meter) for a basic home in Arizona. These costs are competitive with conventional housing.

Larger commercial buildings can incorporate bales for new and retrofit applications. The best use is metal and concrete frame construction with bales as fill.

Widespread use of bales for commercial building will depend on testing and seismic evaluations, which are in their infancy. However, some successful straw bate buildings are:

– Real Goods retail store of Hopland, Calif.,

– Clairborne and Churchill Winery of San Luis Obispo, Calif,

– San Luis Sustainability Group’s architectural offices in Santa Margarita, Calif.,

* Idaho bottling plant,

– Tree of Life Nursery in San Juan Capistrano, Calif., which includes a retail shop, office, seed storage and packing plant,

– community center in Tijuana, Mexico,

– Eco Mundo Resort in Mulege, Mexico,

– medical clinic in Mongolia,

– 5,000-square-foot (450-square-meter) office building housing Save the Children offices in Ciudad Obregon, Mexico, wine tasting room in Ramona, Calif

In Australia, 4-foot x 4-foot x 6-foot bales are being used for commercial projects. Straw bales are also the choice for many animal shelters and barns. Their use for agricultural buildings has spread to Mexico and Europe. At United States International University in San Diego, Calif, students recently built a plastered straw bale amphitheater.

Building codes have been developed for many cities, counties, and states and the nation of Belarus in central Europe.

Expanding the market and assessing full costs for agricultural burning could accelerate bale building adoption. A $3 per ton carbon emission charge on agricultural burning, which would increase to $20 per ton in 2005, might encourage farmers to develop innovative harvesting and marketing schemes for straw. The pollution fee would be comparable to a carbon emission charge levied in Europe.

The revenue collected from fees could be used for health care costs associated with straw burning. It could also help fund bale building research, bale building for lowincome families, education, training and grants for straw bale utilization companies.

Agricultural engineers could develop challenging graduate and undergraduate student research projects related to bale building. Books and videos on bale building, straw bale test data and straw bale engineering, and The Last Straw magazine are available for more information. R

ASAE member David A. Bainbridge is environmental studies coordinator United States International University, 10455 Pomerado Road, San Diego, CA 92131, USA; 858-635-4616, fax 858-6354730, bainbrid@usiu.edu.

Copyright American Society of Agricultural Engineers Mar 2000

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