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Straw-bale construction is a Construction on the North Bytown Bridge in Ottawa, Canada. ...building method that uses A straw bale is a large bundle of straw tightly bound with twine or wire. ...straw bales as structural elements, This page refers to thermal insulation. ...insulation, or both. It is commonly used in Natural building is any building system that places the highest value on sustainability. ...natural building.
History Straw_bale construction was pioneered in State nickname: Cornhusker State Other U.S. States Capital Lincoln Largest city Omaha Governor Dave Heineman Official languages English Area 200,520 km² (16th) _ Land 199,099 km² _ Water 1,247 km² (0. ...Nebraska in the late 19th century, in response to the lack of significant amounts of Lumber is the name used, generally in North America, for wood that has been cut into boards or other shapes for the purpose of woodworking or construction. ...lumber with which to build Houses in Fishpool Street, St Albans, England For other meanings of the word house, see House (disambiguation). ...housing. Often, the straw_bale house was seen as a make_shift structure, to provide temporary lodging until enough funds were available for a "real" Houses in Fishpool Street, St Albans, England For other meanings of the word house, see House (disambiguation). ...house. However, the houses were found to be comfortable, durable, and affordable, and soon became regarded as permanent Houses in Fishpool Street, St Albans, England For other meanings of the word house, see House (disambiguation). ...housing.
Straw_bale Construction on the North Bytown Bridge in Ottawa, Canada. ...construction experienced a re_emergence in the late 1970 was a common year starting on Thursday. ...1970s, after the (Redirected from 1973 energy crisis) United States, drivers of vehicles with odd numbered license plates were allowed to purchase gasoline only on odd_numbered days of the month, while drivers with even_numbers were limited to even_numbered days. ...1973 energy crisis brought issues of Sustainability is an economic, social, and ecological concept. ...sustainability to the forefront. Because it is simple, inexpensive to build and own, made from a renewable resource, and involves few synthetic chemicals, it continues to grow in popularity, especially with See also: DIY Network, a cable TV network. ...do_it_yourself'ers and proponents of Sustainability is an economic, social, and ecological concept. ...sustainability.
Techniques
Wall framing One method of construction uses a post and beam framing system to support the A roof is the top covering of a building that prevents the ingress of weather into the building interior. ...roof. Conventional timber frames, steel frames, and concrete are all common depending on the preference of the builder. Once the structure is in place, the walls are then infilled with straw bales for insulation. This type of structure can easily be analysed for stresses and made to conform to a A building code is a set of laws that specify how buildings should be constructed. ...building code.
Alternatively, the bales themselves may be used as load_bearing walls. Sometimes a combination of both techniques is used, where outside walls have load_bearing straw bales and inside walls are timber_framed.
The building code in the State of New Mexico (1994 ed.) requires that all straw_bale homes be built with rigid structural frames. No other state or regional building code has this restriction. See State of California, Pima County Arizona, etc.
The bales are often laid in running When laying bricks, the manner in which the bricks overlap is called the bond. ...bond like bricks. They may also be staked to increase stability.
The primary cost advantage to building with straw bales is that many buildings are largely built by the homeowner and/or with community involvement through work parties or workshops. While the material to build a straw_bale wall is typically less than that to build a wood frame wall system, a glance at standard home construction cost distribution immediately shows that the cost of the perimeter wall systems replaced by the straw_bale wall system are typically between 5% and 12% of the overall cost of the building.
Plastering Straw_bale walls are typically finished with Stucco is a fine plaster or cement used as a coating for walls or for decoration. ...stucco, sometimes in creative colours or textures. See also: structuralism. ...Structural analysis has shown that the straw_bale/stucco assembly behaves much like a sandwich panel, with the stucco skins bearing some of the load and adding considerable strength to the wall. Plaster for straw_bale walls normally contains a high percentage of lime (often 50 to 100%) because lime allows water vapour to escape from the walls.
Foundation Standard concrete The foundation of a building is the soil or rock on which it sits. ...foundations or slab_on_grade foundations are typical. With load_bearing straw_bale homes The rubble trench foundation, an construction approach popularized by architect Frank Lloyd Wright, is a type of building foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. ...rubble trench foundations are often used. Straw bales have been used to insulate the floor from the slab but this practice has fallen out of favour due to the difficulty of isolating the bales from moisture.
Roofing Many different types of roofs are appropriate for straw_bale building. Some small structures use an An igloo (Inuktitut iglu / ᐃᒡᓗ, house), translated sometimes as snowhouse, is a shelter constructed from blocks of snow, generally in the form of a dome. ...igloo or dome_like structure to create a roof out of straw_bale. More commonly, the roof is constructed from wood or other materials, and attached to the top of the straw walls using a top_plate. Even in this case, however, the roof may be insulated with straw bales.
Characteristics The thick walls, typically 21 inch (530 mm) when plastered, result in deeply recessed windows and doors. Since the bales are not rigid, when plastered they tend to adopt smooth rounded curves. In fact, curved walls are popular as skilled installers can curve the stacked straw_bale walls very easily. These features give straw_bale buildings a characteristic 'curvy' aesthetic.
Advantages
Insulation Straw_bale buildings tend to retain heat very well due to the exceptional insulative value of Straw is the dry stalk of a cereal plant, after the nutrient grain or seed has been removed. ...straw. The theoretical R_Value ( In physics, thermal conductivity, λ, is the quantity of heat transmitted, due to unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of unit area, when the heat transfer is dependent only on the temperature gradient thermal conductivity = heat flow rate / (distance × temperature...thermal resistivity) for a 16.5 inch (420 mm) straw bale was calculated by Joseph McCabe as 52. This is compared with a theoretical R_Value for 3.5 inch (90 mm) of fibreglass (the conventional insulation material used in home construction) of 13. This means fibreglass has an R_Value of about 3.7 per inch and straw bales have about 3.2. Fibreglass commonly achieves R_Values up to 4.2 (R_15 3.5 in (90 mm) fibreglass insulation.
Some lab tests of straw_bale assemblies have found significantly lower R_Values in practice. However, the more conservative of these results still suggests an R_Value of 28[1] (http://www.cmhc.ca/publications/en/rh_pr/tech/tech02_115_e.html), which is a significant improvement over the R_14 of an energy_efficient insulated 2x6 wall[2] (http://www.cmhc.ca/publications/en/rh_pr/tech/tech02_115_e.html). Straw_bale experts suggest that it is possible to approach theoretical R_Values by giving more attention to detailing.
Thermal mass The typical interior finish of a straw_bale wall is either cement or gypsum plaster, or a combination. This wall material provides excellent A thermal mass in the most general term refers to any mass used to absorb and hold heat. ...thermal mass. Thermal mass reduces the thermal swings due to daytime warming and night time cooling, and lessens the need for fuel or electricity to regulate temperature. This is more important at high desert altitudes where a clear sky contributes to both warm days and cool nights. Straw bale construction stores daytime heat and releases it gradually during the cold night. This cold soaked wall then keeps the interior cool during most of the day.
Simplicity Straw_bale building requires little specialised equipment. It has often been successfully used by inexperienced builders working on their own homes.
Availability and cost Straw is widely available, renewable, and generally inexpensive. Because it is a plentiful by_product of An assortment of grains The word grain has a great many meanings, most being descriptive of a small piece or particle. ...grain harvesting, farmers are often willing to provide it at low or no cost. Unlike conventional building which requires co_operation between many fields of specialised knowledge, much of the labour of straw_bale building is fairly simple (hauling bales, applying stucco). This can provide a significant cost savings to the builder/owner who is willing to perform that work themselves.
Resistance to pests Straw bales are thick and dense enough to keep out many kinds of pests. As well, the outer layer of plaster makes them unattractive or impenetrable to animals and insects. Finally, because straw contains no nutrient value, it does not attract pests.
Resistance to fire Although loose straw is quite flammable, once packed into a bale it is too dense to allow enough air for Combustion or burning is an exothermic reaction between a substance (the fuel) and a gas (the oxidizer) to release heat. ...combustion. By analogy, it is easy to light a single piece of paper on fire, but difficult and time consuming to burn an entire phone book. In construction it is critical to have, at a minimum, a parge coat of plaster on all surfaces of the wall.
Typical failure of straw_bale homes involves frame walls set against straw_bale walls without a parge coat. A spark from an electrical short or an error by a plumber ignites the hair_like fuzz on the exposed bale. The flame spreads upward and sets the wood framing on fire causing the wood framing to burn. The typical fire results in little fire damage to bales, but extensive water damage due to the fire suppression activities.
The ASTM E_119 fire resistance test for plastered straw_bale wall assemblies in 1993 passed for a 2 hour fire_wall assembly. In this test a gas flame blows on one side of the wall at approximately 2000 degree Fahrenheit (1100 degrees Celsius) while the temperature of the other side of the wall is continuously measured. The results of this test had no burn_through and a maximum temperature rise of 60 degrees Fahrenheit (15.5 degrees Celsius).
Disadvantages
Limits to structural strength Load_bearing straw_bale walls are typically used only in single storey or occasionally double_storey structures. A dug foundation (basement) is uncommon.
Post and beam straw_bale structures have been used for buildings as large as 14,000 square feet (1,300 m²) and even for a United States Post Office, in Corrales, NM. see: http://www.sarep.ucdavis.edu/NEWSLTR/v5n3/sa_10.htm
Design and construction challenges Straw_bale construction is still considered experimental in many jurisdictions. Building codes may not include it, local authorities may not recognise it, and most contractors will probably not be experienced in its use.
Straw_bale buildings must be carefully designed to eliminate the possibility of moisture entering the walls, especially from above. Successful designs often incorporate roof overhangs that are wider than normal and roof shapes and detailing that minimise the risk of water splashing against walls.
Because straw_bale walls are much thicker than normal walls, there is sometimes a compromise between the size of the building's footprint and the amount of living space.
See also - Voluntary simplicity is a lifestyle considered by its adherents to be a sustainable, ecologically sensitive alternative to the typical, western consumerist lifestyle. ...Voluntary simplicity
- Sustainable living might best be defined as a lifestyle that could, hypothetically, be sustained unmodified for many generations without exhausting any natural resources. ...Sustainable living
- Appropriate technology is a term which refers to using the simplest and most benign level of technology which can effectively achieve the intended purpose. ...Appropriate technology
- Autonomy is the condition of something that does not depend on anything else. ...Self_sufficiency
- An ecological footprint (also called city footprint in connection to cities) is a model and teaching tool that approximates the amount of arable and agriculturally or ecologically productive land area it takes to sustain one human or group of humans, say in a family or city, based on their use...Ecological footprint
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