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Sustainable Building Systems, Inc.


Straw Bale FAQ's

1. Why Build with Straw Bales?

Straw-bale building is an exciting and environmentally-friendly way to build homes, classrooms, greenhouses, commercial buildings, and virtually any other structure. Using straw bales as super-insulating wall material creates houses that are much more fire resistant and energy efficient than conventional wood-frame buildings. These homes are comfortable in hot or cold weather, and save homeowners money on utility bills. If you add passive and active solar design the utility savings are even greater. Depending on the amenities you choose, building with straw can also be much more cost effective than conventional building techniques, and you are making excellent use of an agricultural waste product that would otherwise be burned, adding to our air pollution problem.

 

2. Are There Special Building Codes for Straw-Bale Structures?

Yes — the State of California has a basic set of codes (click here to see the codes), and each county generally has it's own requirements as well. Many other states also have their own codes regarding straw bale construction, with the same types of county-by-county variance, so be sure to check with your state and local Building Departments before designing your structure. If your state or county does not yet have codes, it is often possible to educate them about straw bale construction and have a set of codes created. Contact us for more information on resources and techniques to use when approaching Building Departments with requests for new codes.

 

3. How Does the Insulation Value of Straw-Bale Walls Compare with Conventional Walls?
Straw-bale walls have been tested for heat transmission, and have been rated as high as R-55. A conservative number, used by the California Energy Commission, is R-30. A conventional 2 x 6 wall with fiberglass insulation contains insulation rated for R-19, but when the total wall assembly is considered, scores about R-9. The thermal mass of straw-bale walls tends to keep the buildings a comfortable temperature (usually somewhere in the 70's) year 'round, requiring much less effort and expense to heat and cool.

 

4. How Does the Cost of Straw Bale Construction Compare with Conventional Building?
Conventional building materials are non-renewable and the ecological cost is high. The financial cost is rising also, as fuel prices, manufacturing costs, and lumber-harvesting regulations continue to increase. Depending on your design and the number of amenities, building with straw bales can dramatically reduce the financial cost of your home or other building, while increasing its energy efficiency and decreasing its environmental impact.

 

5. How Are the Bales Used in Construction?
When bales of straw are used as a building material, they can be used in two different ways: loadbearing, and non-loadbearing. As a loadbearing structural material, they are stacked into walls, and the weight of the roof rests directly on the bales. The first U.S. straw-bale houses, built in Nebraska around the turn of the century, were built in this manner, and a number of them are still standing in good condition today.

The non-loadbearing system, which we use most commonly in Southern California, uses a wood or metal post-and-beam frame to support the roof and is designed to meet the structural and seismic codes required by law. The bales of straw are used as in-fill, between the posts, and provide both the insulation and the surfaces for plastered walls.