Straw bale construction: an update

New projects bring this 200-year-old eco-friendly technology closer to the mainstream

by Alice Martinez
[Ed. note: The Earth Times first reported on straw bale home construction in our Oct '94 issue. Since that time, much progress has been made in overcoming the government regulatory hurdles that have prevented the introduction of this renewable, sustainable, environmentally responsible technology. What follows is a brief primer on straw bale building, followed by two articles that describe new efforts to bring straw bale construction to our bioregion.]
traw bale construction is a responsible gesture toward Mother Nature, and one that makes sense. Instead of seeing the dry grain stems burned or buried or simply wasted, this byproduct can be put to good use. Since cereal grains are grown in most states, there would be plenty of straw to go around. Straw is an annual renewable resource, unlike timber that can take 30 or more years to come back.
"Straw is a naturally occurring material, and if used properly in a structure, it's very durable and also an excellent insulator," according to ecological designer Jim Bell. "If a house is built and serves its purpose for 100 years, the major materials, meaning straw, could break down and go back into nature. That's what we need to look toward. In long terms, it's a cradle-to-cradle resource movement."
Straw-bale construction dates back to the last century. Homesteaders in Nebraska started using straw bale to build homes in the late 1800s, out of necessity. With timber in short supply, people turned to the renewable resource they had on hand - straw from wheat, barley and rye harvests.
With the Nebraska method, compressed bales of straw serve as the main support for the roof. Using this load-bearing technique, a continuous beam is placed around the house's upper wall on top of stacked straw bales, and then a roof is put on top of that. (Think of them as big bricks.) Typically, the bales are pinned together with rebar (steel bars). The completed structure is wrapped with chicken wire and stucco is applied, giving the home a conventional external appearance.
Straw bale homes, which have an adobe look to them, are very attractive because the walls are thick and solid, typically 22 inches thick. They're so thermally efficient that utility bills plummet. In one test conducted for the federal government that compared utility bills from conventional wooden homes with bills from straw-bale homes, the straw-bale houses saved as much as 75 percent on utilities.
They're cheaper to build, too. Straw bales cost about $10 a square foot to build, compared to $80 to $100 for conventional homes in San Diego County.

Safe and sane

As far as insects are concerned, straw is usually not on the menu. Straw has virtually no nutrients and common house eaters, like termites, devour wood and not straw.
Once covered with stucco or similar material, straw bale is extremely fire resistant. During a two-hour fire test a section of a wall constructed with straw bale was placed against a furnace. Within five minutes, the temperature shot up to 1,000 degrees Fahrenheit, then 1,750 degrees after 60 minutes. Wood catches fire at 500 degrees. If the wall had been wood, it would have burned. If it had been steel, it would have buckled. As the temperature on the hot side topped out at 1,940 degrees, the cool side temperature rose only 12.7 degrees. Code regulations allow the temperature to increase by as much as 250 degrees and still pass the test.
In a wind test, the equivalent of a 75 mph gale caused no movement in a straw bale structure. At 100 mph, it moved only 1/16 inch.
To prove straw bale's superb insulation benefits, testers examined the material's "R" factor, a numbered rating system used to determine how well a material insulates. Higher numbers indicate relatively better insulation. A six-inch wooden wall with fiberglass insulation, for example, carries an R factor of 19. The average roof rates R30. One bale of straw without any plastering rated R48.

Straw bale evangelism takes off

Special straw bale workshop scheduled for May 24 -26

by Alice Martinez
ob Bolles was not prepared for the response his straw bale exhibit received at last month's EarthFair in Balboa Park. "The response was astonishing," he exclaimed. "We always expect a lot of 'Three Little Pigs - Big Bad Wolf' jokes, and an equivalent number of the genuinely curious. I was simply not prepared for the number of folks who came up to us and said that they had seen a show or article on PBS, Sunset Magazine, Good Morning America, The Wall Street Journal, and the local newspaper. This was obviously a much better informed group than I normally encounter.
"We ran out of literature by noon. Flyers, books pamphlets - even stuff I hadn't planned on giving away - just disappeared." At times, so many people stopped to watch the straw bale house demonstration that the thoroughfare in front of the display was impassable.
Bob is a local building consultant, California Straw Bale Association member and active proponent of straw bale construction. Bob and his Mexican counterpart Roberto Valdez, from El Valle de las Palmas (The Valley of the Palms), Baja California, were part of a charter group of straw bale proponents that met in California Valley (San Louis Obisbo County) in February to hammer out the objectives of an organization dedicated to the development of straw bale construction.
"This isn't just about extolling the (many) virtues of building with this very unique and versatile material; it's mostly about education," Bob explained. "First we have to continue to educate ourselves. Next, we must extend that education to our fellow professionals: architects, engineers, designers - all of the building trades - and the various building departments. Finally, we need to spread the word to the general public, just as we did on Earth Day." As part of this education process, Bob and Roberto have scheduled a Straw Bale Workshop for the weekend of May 24 through 26. Interested participants need to reserve a space early due to the tremendous interest.

Demo in Mexico

Roberto is in the process of forming a non-profit corporation in his home town of Valley of the Palms, 20 miles south of Tecate, Mexico. There he will build a Sustainable Community Center consisting of a variety of housing units and a main building in which to conduct classes in sustainable design and construction. "We have already received inquiries from quite a number of groups and individuals who wish to participate in the building and design of the center, and we are beginning to schedule specific dates for the people to come down and work on the project" he said. "What is particularly encouraging is the number of youth groups who wish to participate, although we expect participation by a wide variety of people who are interested in learning to build sustainably."
One of the most intriguing features of the project is that the construction of the buildings provides a hands-on opportunity to learn about straw bale and other sustainable construction practices. As the buildings are completed, they become sleeping and living accommodations for the participants who will have the opportunity to experience living in a straw bale house.
Bob went on to say, "I am focusing on simple house designs that can be built on either side of the border that are easy to build, low in cost, and yet conform to the Universal Building Code (UBC), and the Safety Guidelines for Straw Bale Houses that were established by AB 1314 which was passed by the State Legislature last year. We are encouraged by the interest in participation by members of the building professions - architects, engineers, and the builders themselves. We are looking forward to their input into the design and construction process.
"At the Earth Day Fair, we talked to a number of people who want to start building their new straw bale home in San Diego County just as soon as possible. You may find 'Construction Grade' Straw Bales at your local lumber yard sooner than you think."

Bob Bolles can be reached at (619) 486-6949 for more information or to register for the workshop.

Habitat for Humanity goes for straw

Earth-friendly, affordable housing, and you can help make it a reality.

by Skip Fralick
aurie Roberts stirred up some excitement when she built the first straw bale house in San Diego County in 1994. Her spark may grow into a flame (sorry, bad metaphor) - her action may inspire the building of many more SB homes in this area. She certainly inspired me, as the environmental director of Habitat for Humanity (HFH), San Diego/Tijuana, to choose straw bale as the appropriate technology for a daycare center planned for Rosarito.

The first straw

The project began in January 1995, when Rev. Laurel Grey of Lutheran Third World Opportunities offered to sponsor a straw bale house for about $5,000 if HFH would get the land, design the building, and supervise 12 high school volunteers coming from Alaska for a week.
I assembled a team whose most experienced member, Jim Danielson, had attended one workshop. Lynn Nelson burned the midnight oil to produce a simple plan for a Nebraska-style load-bearing structure, identical (in terms of interior dimensions) to HFH's 2-bedroom, 480 square-foot homes typically built in Tijuana. Miguel Hernandez, an architect from Rosarito and his wife Virginia organized efforts and approvals in Rosarito, obtained the land, and even fed and housed the Alaskan crew. Straw bales were trucked from San Ysidro to the site. About 140 bales at $4.50 each were used.
During construction, local farmers were excited because they saw that, instead of burning their waste straw, they could sell bales for future homes at say, $1 a bale!
The structure was simple: a 20' by 24' rectangular structure with bales pinned together with rebar and coated with stucco. Two-by-four trusses were used as support for the asphalt tile roof.

Learning pains

Rain became a major obstacle, with record rainfalls the week before and during construction. It was not possible to pour the footing/stemwall until Tuesday of the construction week, and the Alaskans were scheduled to leave on Friday! It looked grim, but miraculously a weather break occurred. The footings were quickly poured, and on Thursday the kids were building the straw bale walls. They left Friday, with straw in their clothes and happy feelings.
But the unusually heavy rains continued into May, slowing down weekend construction. At one point, a man whose sole purpose in life at the time was to cover the straw with tarps at any threat of rain missed his calling, and the bales got soaked. After three months, the bales were again dry, except for a dozen spots which were easily located with a $4 soil moisture probe. These spots were surgically removed and repaired.
Another dramatic episode occurred when vandals ripped out a dozen bales and tried to set fire to the house. Neighbor workers were able to extinguish the flames before penetrating very far into the baled straw. The tight bales didn't allow much air circulation to support a fire (Canada has given straw bale walls a 2-hour fire wall rating). The gaping hole in the wall was replaced with a used 2-glazed sliding door, donated by Dan Cannon of the Building Materials Recycling Center on Otay Mesa. Bob Bolles helped repair the damage and prepare the house for stucco.
Recently, a group of neighbor families has joined in. They're planting landscaping, installing windows and wiring and applying the stucco. A compact fluorescent photovoltaic lighting package is to be donated by United Solar Systems Corp. of San Diego.
The daycare center will serve as a model straw bale home, community meeting center, and organizing point for a grass roots Habitat for Humanity affiliate to be formed later.

The next step ... it's your turn

Tecate is the site of 40 Habitat for Humanity homes served by a unique natural sewage treatment system, called a constructed wetland, with reclaimed water from the wetland irrigating a fruit orchard and community park. The same Lutheran organization that sponsored the Rosarito project wishes to sponsor another straw bale building, preferably in Tecate. This time, the families could co-fund the community center, and would help design and build it. Planning and permitting efforts are underway with construction scheduled to start this June.
Beginning on June 23, 75 Lutheran students are scheduled to camp out and participate. This project will also serve as a demonstration site, and will serve as a Habitat for Humanity organizing center. The Tecate families are a well established community. They have a Homeowners' Association and seem ready to organize another Habitat affiliate to help other low income Mexican families get decent housing by helping themselves. This is what Habitat for Humanity is all about!
You can help provide this much needed housing and get some hands-on experience with this new 200-year-old building technology. Interested volunteers and donors are invited to call Skip Fralick at (619) 565-2603.