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Strawbale

 

Defined
dimensions[1].gif (4373 bytes)A straw bale house is made of straw. Not hay, but straw. Straw is the leftover stems of harvested cereal grains which is sometimes used for bedding material for animals. The bales used for house construction come in various sizes typically held together with two or three strings. The larger three string bale is typically 23" x 16" x 42" and weighs about 80 lbs. The smaller two string bale is typically 18" x 14" x 36" and weighs about 55 lbs. The bales are laid flat and stacked like bricks and are reinforced vertically with rebar or some other material suitable as a pin. The straw bales themselves can be load bearing although some builders may prefer to build a post and beam frame. The straw bales are typically sealed by finishing the outside wall with stucco cement and plaster on the interior.

History
Although stone age dwellers probably used grass huts to live in, these huts were not made of straw bales. Here in the United States, the earliest record of straw bales homes were built in the 1890's by settlers in the Sandhills of Nebraska. This area was void of trees, roads or railways and settlers were probably forced to build out of local materials. Secondly, most settlers didn't have the money to build a more conventional style of house and these houses were initially built only to be temporary.   They were plastered on the inside and eventually stuccoed on the outside. It's interesting to consider if these settlers realized what an energy efficient house they were building. The practice of building a straw bale house seemed to be common in this area for a short time. As other building materials such as wood became more prevalent, the straw bale technique waned. Although these houses were frowned down upon as a inferior building method, today they have plenty of merit.

What are the advantages of building a straw bale house?

  1. Cost - Depending upon what fixtures go into the building, costs run anywhere from $5 to well over $100 a square foot. In general though, you could probably build a straw bale for about the same cost as a cordwood home. Typically the only part of the house that is different from either building method is the walls. Costs vary depending upon whose labor you use (yours vs. paid labor), windows, doors, fixtures, etc. The more you can do yourself the less it will cost out of pocket.

  2. Energy Efficiency - Straw bale walls provide excellent R values of about R-28 (From The Environmental Building News). Plastering the interior wall of a straw bale house adds some thermal mass as well. Both superior insulation and thermal mass give you a good start at a very energy efficient house. Just make sure to insulate the heck out of your roof to match the efficiency of your walls.

  3. Ecology Friendly - Straw is readily available and has little if any impact on the well being of Mother Earth. Using a natural insulator as a wall is a great way to reduce consumption of non-earth friendly building materials. Also the amount of energy that it takes to make straw is substantially less than other building materials used to build a stick frame house.

  4. Easy to Build - Just like cordwood, almost anyone can build a straw bale house. Basic carpentry skills and a little muscle is all that is needed.

  5. Pride - There's a lot of pride and joy associated with building your own house.

  6. Easy Availability - Straw can be found just about anywhere grass grows. It's abundant, it's cheap and easy to get.

 

What are the disadvantages of building a straw bale house?

  1. DC_str2[1].jpeg (12201 bytes)Moisture - Case studies have shown that if the walls are not allowed to breath properly, moisture buildup within the wall will lead to the straw rotting. The houses that were built 100 years ago in the Sandhill region of Nebraska is fairly arid. I would have no reservations building a straw bale house in an arid region but I would be very cautious in areas that have high humidity. Although compost piles are good in most cases, you wouldn't want your walls to turn into that rich, loamy stuff.

  2. Resellability - Just as with cordwood, people may have reservations about buying a house made out of straw. (Those darn fairy tales!) If people take the time to find out about what makes a straw bale house tick, I doubt they would be as concerned.

  3. Building Permits - Depending upon where you live and the building code standards, you might have a tough time getting approval. There are quite a few good documents that can help make this a less painful procedure. "Straw Bale Construction and the Building Codes" by David Eisenberg is a good reference for those who need some help with a building permit.

  4. Fire Hazard? - Only before the plaster and stucco are applied. According to Mother Earth News, Jan. 1996, once the walls are sealed tests show that 18" straw bale walls survived fire penetration for more than two hours. Unfinished walls only survived for 34 minutes.

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