STRAW OR HAY?
Straw is an agricultural by product, the dry stalk of a cereal plant, after the nutrient grain or seed has been removed. Straw makes up about half of the yeild of a cereal crop such as barley, oats, rice, rye, or wheat. Intimes gone by, it was regarded as a useful by product of the harvest, but with the advent of the combine harvster, straw has become more of a burden, almost a nuisance to farmers.
Hay is grass or legumes that has been cut, dried, stored and used for animal feed. Hay is fed when there is not enough pasture or rangeland on which to graze an animal.
WHAT ABOUT MOISTURE AND ROTTING?
Both wood and straw can rot if wall moisture content rises above about 70% for extended periods of time. New information from Canada and the
U.S. strongly suggests that all superinsulated homes (of which strawbale homes are only one type) must be designed to avoid moisture buildup or rotting can occur. Some data on the degradation of wood even suggest that our past and current understanding of the dynamics of moisture and vapor barriers is incomplete, and that many newer homes with standard insulation levels which employ moisture barriers are at risk due to inappropriate installation of the barriers. Strawbale enthusiasts are, if anything, more knowledgeable about both the dangers of moisture and are more familiar the technques of moisture control than most builders of conventional homes. The final word regarding moisture is that it is a design problem that is shared by both wood and straw, and that buildings utilizing strawbale walls are no more prone to moisture degradation than houses built of wood.
WON'T STRAW BALES BURN EASILY?
Loose straw, burns easily, just like wood shavings. Baled straw tends to simply smoulder, like trying to burn a phone book. The key factor is how easily a fire can obtain oxygen; tight baling of the straw severely limits a free flow of oxygen. Most importantly, strawbale houses are traditionally covered with stucco. Tests have shown time and again that stuccoed strawbale houses have a much greater resistance to fire than do conventional wood structures. Strawbale structure fire tests have shown that stuccoed strawbale construction is able to withstand temperatures of 1800 degrees Farenheit for over one hour with no structural damage, which is sufficiently fire resistant for stuccoed strawbale to qualify as a commercial building material. The growing list of county building departments which have approved strawbale construction is indicative that strawbale construction is not only safe, but is in fact safer than conventional wood construction.
WHAT ABOUT BUGS AND PESTS?
Being comprised of the stems of plants, Straw contains no food value. Bugs see straw as being a lot more like the
Desert than a leftover pizza. Termites, the bane of wood homes, don't have the right digestive processes to consume straw and can accurately be described as disinterested. The existence of sound, longstanding strawbale houses has proven that this is true. There are additional non toxic measures that can be taken if concerned. Additionally, the plaster skins on the inside and outside of the walls prevent access for any other pests, unlike tradional wall assemblies.
R-value is a measure of apparent thermal conductivity, and thus describes the rate that heat energy is transferred through a material or assembly. Materials are given a number, the higher the number the greater the insulation quality. In the mountains of Colorado the R-value code requirement of a wall is 21.
A straw bale wall is difficult to give an exact measurement, based on tightness of each individual bale, how the bales are oriented and so on. However the R-values range from 30 to 50 depending on orientation and other factors.
WHAT MAKES STRAW BALE HOMES SO APPEALING?
Straw bale houses are commonly very tight building envolopes with the use of plasters. Using a plaster for wall coveringsHas many advantages and is another perfect marraige with strawbale construction. First, a plaster is for protection from the elements, fire, rain,sun, impact,etc...
The plaster also adds to the structural integrity by adding compressive and lateral strength. Plaster also controls water vapor, air infiltration, sound and acts as a thermal storage. There are many different materials used for plaster such as earth, lime, gypsum, and cement. Each material has it's advantages and disadvantages. Living in harsher climates may lead folks to a lime or cement stucco on the exterior and earthen(clay) ,lime, or gypsum on the interior.
IS A STRAW BALE HOME MORE EXPENSIVE THAN A STICK FRAME HOUSE?
It depends on what you are evaluating, it's not an apple to apple comparison. Straw bale homes have a higher insulation value, greater mass, have better indoor air quality and have far less toxic chemicals off gasing then the traditional home we have been building for decades. If we were to build a stick frame house that would meet all of these high performing goals then the stick frame house would be nearly twice as much as it's Straw bale comparison.
Finding ways, techniques and exceptional management and experience gives Straw & Timber the best chance to get close to competing with the standard home market.
The materials are cheaper on a straw bale home and labor tends to be more, it's a hand build house. So the up front cost of building a Straw bale home compared to a standard code built stick frame home will likely be more. However over time the utility costs of a well designed straw bale home are significantly less.
We should also consider the true costs of the materials that we use. These costs are unforseen such as the environmental impacts from material extraction, transportation and eventually disposal. It's worth thinking deeply about the materials which we choose to use and all the risks associated.