Straw Bale Construction
The idea of building anything permanent out of straw may seem laughable. After all, we all grew up with the tale of the Three Little Pigs. ~ ecosustainablevillage.com
But read on - you may be surprised and intrigued. Straw bale construction uses baled straw from wheat, oats, barley, rye, rice and others in walls covered by earthen or lime stucco. Straw bale are traditionally a waste product which farmers do not till under the soil, but do sell as animal bedding or landscape supply due to their durable nature. In many areas of the country, it is also burned, causing severe air quality problems. It is important to recognize that straw is the dry plant material or stalk left in the fIeld after a plant has matured, been harvested for seed, and is no longer alive. Hay bales are made from short species of livestock feed grass that is green/alive and are not suitable for this application.
History:
Straw, grass, and reeds have been used as building materials for centuries. Straw houses have been built on the African plains since the Paleolithic. Straw bales were used in construction 400 years ago in Germany; and straw-thatched roofs have long been used in northern Europe and Asia. In the New World, teepees were insulated in winter with loose straw between the inner lining and outer cover. Straw-bale construction was greatly facilitated by the mechanical hay baler, which was invented in the 1850s and was widespread by the 1890s. It proved particularly useful in the Nebraska Sandhills. Pioneers seeking land under the 1862 Homestead Act and the 1904 Kinkaid Act found a dearth of trees over much of Nebraska. In many parts of the state, the soil was suitable for dugouts and sod houses. However, in the Sandhills, the soil generally made poor construction sod; in the few places where suitable sod could be found, it was more valuable for agriculture than as a building material. The fIrst documented use of hay bales in construction in Nebraska was a schoolhouse built around 1896. Unfenced and unprotected by stucco or plaster, it was reported in 1902 as having been eaten by cows. To combat this, builders began plastering their bale structures; if cement or lime stucco was unavailable, locally obtained "gumbo mud" was employed.
Considerations:
This technique for constructing walls has been recently revived as a low cost alternative for building highly insulating walls. The technique has been applied to homes, farm buildings, schools, commercial buildings, churches, community centers, government buildings, airplane hangars, well houses, and more. Two basic styles of straw bale construction have been used: post and beam construction with straw bale infill, and structural straw bale construction or "Nebraska" style (the weight of the roof is supported by the bales). In most areas, a building permit is much more readily attainable for the infill method, where the bales themselves are not load-bearing.
Facts
Straw bale construction exhibits R values from R-30 and up to R-45. The bales are typically covered with concrete mortar/stucco or earthen/lime plaster, achieving a high degree of fire resistance. Consider that a bale is like a phone book. If you rip out the pages one by one and light them on fire, they will burn: so will loose straw (although not very well due to the high silica content). If you hold a lighter under the entire phone book, however, you will likely run out of fuel in the lighter before the book catches fire because there is no oxygen in between the pages to support the fame. The same is true for the baled straw. Now put the two systems together: thick plaster on both sides of the wall and dense, oxygen deprived bales inside. This combination makes for a very resistant wall and one which has a much better chance of survival in fire situations, as well as resisting insects, rodents and water. Andrew Morrison, Strawbale.com
