Thursday, March 18, 2010
Eco-friendly straw bale house construction
A lot is heard lately about “green” home construction and houses that are “eco-friendly”. Most of the homes in question use conventional frame construction with more insulation, more efficient electrical appliances and low-flow water fixtures. Truly earth friendly house construction goes well beyond these measures.
A popular “green” construction method in the western US is the straw bale house. This technique is starting to gain popularity across the country and worldwide because of its ease of construction and use of an agricultural waste material. More states and cities are adding straw bale construction codes every year.
Straw bales used for home construction must have less than 20% moisture content and be tightly compacted(they should not bend if lifted by one string). This also makes the bales quite fire resistant, as they contain little oxygen, especially after being encased in plaster and/or stucco. A bale home has approximately three times the thermal insulation of a conventional frame home. Sound insulation is also much better that with typical frame construction. Another advantage of straw being a natural material is no off-gassing, which can be a problem with many insulating materials for sensitive people.
People often wonder about the durability of straw bale structures. Because they are encased in waterproof stucco on the outside and “breathable” plaster on the interior, the bales are fully protected from water and do not rot. The highly compacted bales have low oxygen content and are much more fire resistant than conventional construction. Bale homes survive well in high-wind and earthquake zones. Many straw bale homes from the 1800’s are still standing in Nebraska and Europe.
Many resources are available to learn about straw bale home construction on-line. Many books have been published on the subject as well. Straw is an agricultural waste product in many parts of the world and is often burned, adding to the greenhouse gas problem. More bale-friendly building codes could help both the earth and home owners.