STRAW BALE CONSTRUCTION
By: Catherine Wanek
Could it be that the house of the future was invented a century ago? In the 1890s, pioneers of the sand hills of Nebraska found themselves building a new life on a treeless prairie, and from necessity began building their homes from bales of straw. Now modern day pioneers are choosing straw bale construction for its many advantages -for people and the planet.
Straw bales offer excellent insulation. At R 2.7 per inch, an eighteen-inch wide bale equals R-48. One California study indicated that such a “super-insulated” straw bale home could save as much as 75% of heating and cooling costs! This translates to direct dollar savings for the homeowner, and a corresponding reduction in the use of fossil fuels and CO2 emissions.
Construction costs can also be reduced when building with straw bales. They are cheap to buy and easy to build with. Stacked like huge bricks, straw bale wall systems can be erected quickly without much building experience and few power tools. In a “barn-raising” type party, it’s common for all the straw bale walls in a modest size structure to be erected in a single day.
Building with bales can also cut down on cutting down trees by reducing lumber used in typical “stick frame” construction. Straw is available wherever grain crops are grown, and is annually renewable. In fact, it’s considered an agricultural waste product, and in many parts of the world is simply burned in the fields. The millions of tons which go up in smoke every year cause a great deal of air pollution. It makes sense to bale this nuisance, and turn it into an energy-efficient resource.
Those concerned with indoor air quality also appreciate straw bale buildings for their “breathability.” A non-toxic product itself, bales allow a gradual transfer of air through the wall, bringing fresh air into your living environment, especially when combined with a natural plaster. And you can forget about neighborhood noise, too. Straw bales are so sound proof, one Nebraska pioneer family was found playing cards in their kitchen, oblivious to the roar of a tornado which had just blown through the town.
Two types of bale wall systems are commonly built. In a “post and beam” building, a wood, steel, or concrete framework Is erected and bales are placed in the walls as insulation. Bale systems can also bear the weight of the roof, as evidenced by the historic Nebraska homes which were all load-bearing. In this case, a top-plate is laid above the bale wall and secured to the foundation by metal rods and/or strapping. The roof is then attached to the top plate. In either system, the bale courses are stacked in a “running bond,” and pinned with rebar, wood, or bamboo stakes. For added strength, chicken wire is commonly wrapped inside and out, and sewn tight to the bales. Then an earth plaster or cement stucco is applied as a finish. However, bales will also hold plaster without wire mesh.
Under the watchful eye of instructor Peter Fust, an EPSEA workshop student restrings bale to make 2 half bales.
Peter Fust of Black Range Films, demonstrates the attachment of bamboo poles which add strength to the bale wall.
Seperating the newly strung half bales
Common questions about straw bale homes include concerns about fire, moisture, and insects. While individual stalks of straw will burn, when condensed into bales, they actually resist combustion, due to lack of oxygen. It’s like trying to burn a phone book. At a certified laboratory in New Mexico, a plastered straw bale wall system easily passed a two-hour fire test, which is required for commercial construction. Liquid moisture is a problem in bale walls, as it is in any wall system. But with a proper foundation, roof, and finish plaster, straw bale buildings can last indefinitely, as nearly century-old homes in Nebraska prove. Anecdotal evidence indicates no problem with bugs.
Building codes have been developed for both “post and beam” and load-bearing straw bale construction. In New Mexico, Pima County, AZ, and several counties in California, getting a building permit for a straw bale house is almost routine. Farmers Insurance Group will insure a bale home at preferred rates and other companies are following suit. And straw bale houses are gaining acceptance with Fannie Mae and HUD.
Black Range Films has released its third video in a series on “Building With Straw Bale”. Their latest production Straw Bale Code Testing will assist anyone, including code officials in dealing with the permitting process.
The Black Range is now the publisher of “The Last Straw” newsletter.
NEWS: Black Range – Natural Building Resources are now known as Straw Bale Central (new name – same great folks)
More LINKS to Straw
Introduction to The Last Straw: http://www.netchaos.com/tls/index.html
Nice collection of general strawbale information, plus strawbale happenings in the Rocky Mountain West. http://www.pcisys.net/~moxvox/straw.html
The Thermal Resistivity of Straw Bales for Construction
Joe McCabe’s master’s thesis http://solstice.crest.org/efficiency/straw_insulation/straw_insul.html
Development Center for Appropriate Technology’s website:
“Addressing Institutional Barriers to Straw Bale Construction”
Straw Bale House:
A Straw Bale student project. http://www.sccs.swarthmore.edu/~csunami1/straw.html
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