The Pros and Cons of Straw Bale Wall Construction In Green Building
Following are some pros and cons of building a straw bale house. Like any building material, it is always best to evaluate your needs and your goals before committing to a particular material. Green building offers a wide range of options in achieving energy efficiency. When appropriate for your project, straw bale construction has many benefits.
Advantages of straw bale construction
1. Straw bales are made from a waste product. Once the edible part of the grain has been harvested (such as wheat or rice), the stalks often become a disposal problem for farmers. By bailing the straw, a new life is given to the material. The farmer makes some money by selling the bales and the homebuilder gains an excellent insulation and building material.
2. Homes insulated with straw bale can have insulation values of R-30 to R-35 or more. The thicker the bale, the better the R-value.
3. Straw bale walls are at least eighteen inches thick. This adds aesthetic value to the home as thick wall are expensive to achieve with conventional construction. The thickness of the wall helps to reflect sunlight throughout the room.
4. Due to the thickness of straw bale walls, every window can have a window seat or shelf. This becomes both an aesthetic and practical design element.
5. The concept of straw bale construction is easily understood by even novice builders. With supervision by one knowledgeable straw bale trainer, first-time builders can assist in the construction process. This not only spreads the word about straw bale construction, it also means that the homebuilder can save money by using a volunteer crew to help raise the walls.
6. Straw bales have a low-embodied energy. This means that very little energy was used to manufacture the product as sunlight was the main energy source for growing plant. The only energy needed to make a straw bale is in the bailing process and the transportation to the worksite. Other insulation materials, such as fiberglass, require a substantial amount of energy to produce.
7. Straw bales are 100% biodegradable—when the time comes. Straw Bale homes can last over 100 years if properly maintained. At some point, all structures will eventually be replaced. When the time comes, the straw bales can be plowed back into the earth. Fiberglass, on the other hand, becomes a disposal problem.
8. Straw bale walls can be carved with a knife or chainsaw. Openings around windows or doors can be bullnosed to a nice radius. Bales can also be finished to a sharp angular edge. Nichos can also be carved into the bales.
9. Despite what might seem logical, properly constructed walls made from straw bales have proven to be more flame retardant than conventional wood-frame construction. This is because the bales are dense and tend to just smolder when the ignition source is removed.
10. Straw bale insulation is the most effective in climates where heating and/or cooling of the home is essential for comfort.
11. Straw bale homes can be beautiful as the natural material lends itself to multiple architectural styles.
Disadvantages of Straw Bale Construction
1. SInce it is not a conventional building material, the contractor or do-it-yourselfer will need to learn new construction techniques. Although not difficult, they are different.
2. If straw bale building codes are not part of your local codes, it may be a bit more work to get your plans approved. Contact others in your area and see if they can suggest local architects or engineers that are used to working with natural materials and see they can stamp your plans and help with the approval process.
3. Straw bale walls need to be kept dry as moisture is detrimental to not only straw, but to many building materials. Moisture entering the bales from the roof above is to be avoided at all cost. If the walls of your straw bale home are kept dry, they will last for the life of the building.
4. Areas of extreme humidity and rain my not be appropriate for straw bale construction.
5. Due to the thickness of the walls (usually around 18-20 inches), more of your overall square footage will be unusable due to it being within the wall space.
6. If straw bales are not available within a few hundred miles of your construction site, the cost of shipping them, along with the potential pollution from the transportation, must be taken into account.
If you would like to learn more about straw bale home construction, take a look at the DVD video and book called “Building With Awareness: The Construction of a Hybrid Home.” It is available online and in book stores.
Article and photo by Ted Owens