- Green Technology
Straw Bale House Construction - Part 2
History of straw bale buildings
At the end of the nineteenth century, some of the first straw bale buildings were constructed in Nebraska, USA. They were constructed on the flat lands where timber and stone were hardly available. The first straw bale structure was used as temporary shelter. However, the later buildings proved to give cozy living conditions with thick straw wall insulation, which was keeping them cool in summer and warm in winter. With straw bale building method, load bearing straw bale structure became very famous in Nebraska and it was being called as “Nebraska style”.
Straw bale houses have carried on with its growing popularity because of its enjoyable construction method. In 1940’s this progress slowed due to the war and straw bale construction was wiped out for thirty years. In the 1970’s and 1980’s old straw bales, building method re-appeared and it was being refined. The new advance methods were circulated in the market, which promoted the utilization of straw as infill material in timber and “Nebraska style” building. By the start of 1990, the straw bale building technique was experiencing bigger development in America, especially in self-builders. Whereas straw bale building got its popularity in Britain by mid of 1994.
What Is Straw?
The straw has tubular plant structure between the grain head and the root crown, whereas hay is a straw that involves carbohydrate and grain. In that carbohydrate contain rich fruit of a plant, and grain contains a high amount of protein. Hay is used as a food source for horses and straw is used for buildings.
The inside structure of straw is tubular, efficient and tough, which contain hemicelluloses, cellulose, silicon dioxide (Ash) and lignin. These have high tensile strength. However, the proportion and chemistry of the components differ with the type of plant and weather exposure.
The following proportions are the average value of rice straw.
- Cellulose: - above 40% of volume
- Hemicellulose: - about 25% of volume
- Silicon dioxide (Ash):- about 20% of volume
- Lignin: - about 15% of volume
What Are Bales?
Bales are bunches of straw compacted and fasten into rectangular blocks. Steel wire or polypropylene twine is most commonly used to tie the bales. Building bales sometimes might be tied into smaller two-string or larger into three-string. The large size rectangular and circular bales are extremely used in building structures industrialized countries. Because of their large size, they require machinery and equipment, such as forklift to move and place them. The bales are commonly placed flat, i.e. longest dimension parallel to the wall and the shortest dimension vertical. In addition, it can place on the edge as well, i.e. shortest dimension horizontal.
Why build houses with straw bales?
Straw bale is renewable material, which is easily obtainable by cultivable farming. It has high insulation values. It's ‘U’ value is 0.13 W/m²K for a 450mm thick bale, which is fulfilling the requirement of current building regulation. It is capable of carrying two story building load. In today’s market straw bale is used as a modern construction material because of its low environmental impact and wonderful thermal properties.
Straw is known as a renewable material, it is possible to replace renewable material by natural methods at the same or faster speed than its consumption by humans. For instance, farms in the United Kingdom generate three million tons of straw by growing barley and wheat. A conventional three bedrooms house consumes five tons of straw. So, there is sufficient straw obtainable in the United Kingdom to construct 600,000 homes year on year. Straw is known as a carbon positive footprint. As plants cultivate they take CO2 molecules from the environment. From the photosynthesis process, plants can apart the CO2 atoms to form the single carbon atom. They give back the oxygen to the environment and hold the carbon to create complex sugars such as cellulose.
What are Straw Bale’s Benefits?
It has low embodied energy
Straw is by-product, it grows from the crop. It chopped from the field or may be it take off from the field by baling. Whereas bricks need a large amount of energy in its manufacture process.
It has high level of thermal insulation
Highly insulated straw bale walls assist in keeping a building cool in summer and warm in winter by saving energy.
It is a renewable material
Straw is a renewable material, which grows every year. Whereas block and brick are not classified as a renewable material.
It is a cost effective material
Straw is an agricultural product, which is very cheaply available. The largest saving behind the straw bales is it save heating and cooling expenses for the entire life of the structure.
It emits Low carbon
Straw bale would emit very low carbon during its construction phase. Whereas conventional construction emits approximately 50 tons of carbon dioxide.
It has got good sound insulation
Straw bale houses are incredibly quiet. The thick straw bale walls deaden sound.
It is non-toxic
Straw bales are non-toxic in nature. It doesn’t emit any hazardous gases.
It is a user-friendly
Straw bales are very light to carry, easy to mold and quick to build.
Was this article informative and useful?
© 2017 Ashish Dadgaa