studs might be insulated to R- 12 or R-20, but the wooden studs themselves only offer approximately R-1 per inch, or R-5.5 for a common 2-by-6-inch stud. The thermal efficiency of the building is broken by these regular “cold bridges.” Infrared photographs of frame homes taken on a cold day will show the outlines of the studs as cold strips on the interior wall surface. Problems can also arise in frame walls with settling and improper installation of various insulation materials, creating cold gaps. In a bale wall, only the window and door openings create cold bridges.
Reduce Your Heating and Cooling Bills
By significantly reducing the energy required to heat and cool your home, straw bale walls will save you a great deal of money over your home’s lifetime.
Lower Construction Costs
An entire chapter is devoted to “The Hotly Debated, Often-distorted Question of Cost,” so here we will only point out that the materials used to create bale walls are less expensive than other common wall systems. By doubling as both wall structure and insulation, they play a dual role at a very reasonable cost. Whether you can translate this lower cost into a less expensive building project will be determined by your particular plans and how you realize them.
A significant cost advantage can be realized if you raise your own walls without the assistance of professional builders. It takes much less specific knowledge to build a bale wall than a wooden-framed wall, and you can save money by doing it yourself.
Cost will always be an important factor as we consider different building possibilities in this book. Our aim is to help you to build to your needs while meeting your particular budget requirements.
Design Benefits
Many alternative building systems require builders to adapt to new and often complicated construction techniques in order to achieve the benefits of the system. These same buildings can also require the occupants to adapt to new living conditions and configurations. These adaptations are not necessarily undesirable, but they are a significant factor in the decision-making process.
Straw bale construction is easily adaptable to a wide variety of design configurations — from the norms of traditional suburban homes to round, vaulted, or other unusual designs. Regardless of the design, the insulating and cost benefits of straw bale walls are always evident. Where building codes require new homes to blend with current fashions, or where home-builders prefer established designs, straw bales can be used to upgrade the performance of those homes. At the same time, bales leave the field wide open to spatial innovations of all stripes.
Beautiful, Adaptable Walls
Straw bale walls can be built to suit a variety of esthetics. From rounded and lumpy with an old world feel to straight, elegant, and modern, straw walls can take on many shapes and textures depending on how they are detailed. Finishing choices are almost unlimited, and different effects can be applied to different walls in the same home. Especially attractive to many owners and builders are the deep window openings, which can be finished in a number of ways to provide seats, plant shelves, or decorative sills.
1.3.a - d: These four homes show that bale buildings are in no way limited in their design.
Bales Suit Human Dimensions
Bales are unusually well-suited to human dimensions, because the bale sizes were created for farmers to be able to lift, carry, and work with them effectively. This translates into useful construction dimensions too. A single bale makes a comfortable seat, two bales a comfortable stool, and three bales an excellent leaning post. These friendly dimensions can be incorporated into your design in unique and comfort-making ways.
Quiet and Comfortable
Straw bale walls are excellent sound barriers, making them an attractive choice in urban settings where ambient noise can be distracting and unhealthy for occupants.
Inside a straw home, the nature of the walls provide a pleasant sound qualitiy unavailable from flat, drywalled rooms. Sound and light behave very differently inside spaces that are not entirely flat and angular, resulting in a calmer, warmer, and more relaxing atmosphere.
Environmental Benefits
Straw bale construction can help to reduce the environmental impact of a building project in several ways:
• reduction of energy needed to heat and cool bale buildings
• annual renewability of straw resources
• low embodied energy
These factors combine to make a persuasive environmental argument for the use of straw bale wall systems. Reduced energy consumption for heating and cooling means less fuel is required and fewer emissions are produced from burning finite natural resources. Straw harvesting is much less energy-intensive than lumber harvesting and the manufacturing of insulation and other products used to build frame walls. The energy expended in straw production is already producing grain crops, resulting in a two-for-one energy saving. Straw is available locally in a wide variety of climatic regions; using locally produced bales saves energy that would otherwise be consumed in transportation.
Straw can be grown and harvested annually — unlike forests that take upward of 40 years to re-generate and rarely return to their former levels of production. Straw needs little processing to be used for building, and straw production is very decentralized; there are few regions that are not within a reasonable shipping distance of a straw supply.
1.4: By bringing the straw bale walls into the living space, you can wrap yourself in the warm, comfortable contours that attract so many people to bale building.
Using straw bales for building could also reduce the amount of straw that is burned off each year, considered waste. While many North American jurisdictions are starting to ban the burning of straw, tonnes of straw are still burned, adding un- wanted emissions and particulate to our atmosphere.
What is Embodied Energy?
Embodied energy, a term that is slowly making its way into the consciousness of the building industry, is the amount of energy used in producing a building material. In some calculations, only the energy directly used in harvesting and producing the material are included. In other more thorough studies, the calculations include harvesting, production, transportation, storage, life cycle, recycling, and disposal. But no matter how you calculate embodied energy, baled straw is one of the best materials available.
A Good Wall System for Noise Reduction
Most people who have been in a straw bale building have had the sensation that interior sounds somehow seem louder. Interior sounds are more distinct because they are not being drowned in background noise coming from outside. This is a clear indication that a straw bale wall works very well as an acoustic insulator. It does so because it is an almost perfect example of a damped cavity surrounded by two not-so-stiff membranes with sufficient mass — a far more effective method, weight for weight, than structures based on pure mass, like brick walls.
The anecdotal evidence of good sound insulation is supported by a test executed in the summer of 2003 at the acoustic lab of the Eindhoven Technical University. The test and the facility meet ISO 140-3 standards for testing the sound isolation of building aperture closures (i.e., windows). The test