As a building material, straw is sustainable, plentiful and inexpensive. In many places, straw is an unwanted farming waste product - over 200 million tons of waste straw a year is generated in this country alone. When waste straw is burned in the field, it contributes to air quality problems and the destruction of the ozone layer. By using waste straw as a construction material, however, this source of pollution is eliminated.
Straw bale construction uses bales made from the leftover stems of harvested grain, mostly rice. The bales can be used in many ways, but the most common techniques are post and beam systems and structural bale systems.
In the post and beam system, a framework of timbers supports a building's roof, and straw bales are stacked between the weight-bearing timbers to make up the insulated wall.
In the structural system, the bales themselves are stacked directly together - much like bricks are used - to support the weight of the building and roof. No timbering is needed.
In both cases, straw bales are stacked on a foundation to prevent damage from the seepage of water. They are usually held together with rebar pins that skewer the bales. After wiring and plumbing, the walls are stuccoed on the outside and plastered on the inside to seal them from moisture. The roof is commonly a conventional wood frame.
Straw bale buildings have highly insulated walls and boast low building and maintenance costs. They drastically reduce the amount of wood needed to construct a house, instead converting an agricultural waste product into a valued, sustainable building material. Straw bale walls are waterproof, extremely fire resistant and pest free. Because construction techniques are so simple, a community house-raising effort can build most of a straw-bale house in a single day.
The structural style of straw bale construction is also known as the "Nebraska" style, since the technique originated in that state around the 1880s, following the invention of the steam-powered baler. Some homes from that period still remain of use after more than a century. A once-popular style of building that fell out of favor in the 1950s when mass-produced construction materials began to emerge, straw bale is making a comeback.