Straw-bale construction
Straw-bale construction is a building method that uses bales of straw (usually wheat[2] straw) as structural elements, building insulation, or both. This construction method is commonly used in natural building or "brown" construction projects. Research has shown that straw-bale construction is a sustainable method for building, from the standpoint of both materials and energy needed for heating and cooling.[3]
Advantages of straw-bale construction over conventional building systems include the renewable nature of straw, cost, easy availability, naturally fire-retardant and high insulation value.[4][5][6] Disadvantages include susceptibility to rot, difficulty of obtaining insurance coverage, and high space requirements for the straw itself.[7] Research has been done using moisture probes placed within the straw wall in which 7 of 8 locations had moisture contents of less than 20%. This is a moisture level that does not aid in the breakdown of the straw.[8] However, proper construction of the straw-bale wall is important in keeping moisture levels down, just as in the construction of any type of building.
Problems with straw-bale[edit]
Two significant problems related to straw-bale construction are moisture and mold. During the construction phase, buildings need to be protected from rain and from water leakages into the body of the walls.[49] If exposed to water, compressed straw may expand due to absorption of moisture. In turn, this can cause more cracking through which more moisture can infiltrate. Further damage to the wall can be caused by mold releasing potentially toxic spores into the wall cavities[50] and into the air.[51] In hot climates, where walls may have become internally dampened, internal temperatures may rise (due to decomposition of affected straw). Rats and mice can infiltrate straw bale homes during construction, so care must be taken to keep such animals out of the material. Other problems relate to straw dust which may cause breathing difficulties among people with allergies to straw or hay.[52][53][15]
Several companies have developed prefabricated straw bale walls. A passive ecological house can easily be assembled with those panels.