Farming Magazine - May, 2013

FEATURES

Straw Structures

By Katie Navarra
Volunteers learn how to tie half bales.

Volunteers learn how to tie half bales.
Photos courtesy of David Arkin, Arkin Tilt Architects Ecological Planning & Design.

Contrary to the children's nursery rhyme, "The Three Little Pigs," a well-built straw bale structure cannot be blown down by a huffing and puffing Big Bad Wolf or Mother Nature's severe storms.

Straw bale structures first gained popularity over 100 years ago on the plains of Nebraska and in some places in Europe. Storage sheds, barns, schools, homes and even grocery stores have been built using straw bales. Some of these original structures are still standing and in use today.

The Straw Bale Building Registry maintains a list of buildings voluntarily added to the registry by the structure owners or builders. As of early April 2013, 1,604 structures have been registered worldwide. The U.S. and China lead the registry, with 733 and 597 homes, respectively. Within the U.S., California and Colorado lead the registry with 125 and 88, respectively.

The registry website (http://sbregistry.sustainablesources.com) estimates that there are actually 10 times as many straw structures in use today than have officially been registered.

Straw structures provide housing

Interns from across the U.S. and around the world are eager to live in the two-story straw house at Apple Pond Farm and Renewable Energy Education Center in Callicoon Center, N.Y., near the Catskills.

Owners Dick Riseling and Sonja Hedlund, partners and owners of the farm, built the house for less than $5,000 using organic materials, most of which came directly from the farm.

This straw bale home in Santa Cruz, Calif., was named the 2012
Fine Homebuilding Home of the Year.

This straw bale home in Santa Cruz, Calif., was named the 2012 Fine Homebuilding Home of the Year.

The structure's foundation is an existing knee wall from a silo that had burned. Clay mined from the farm was used to mortar the structure together.

In addition to providing a low-cost building option, the straw house is extremely energy-efficient. "The R-value [insulation rating] is up to 54 in the walls, and the R-value is 80 in the roof," Riseling said. Since finishing the building in 2005, he added that it has cost less than $50 a year for heating and lighting the straw house.

Since a majority of the building materials came directly from the farm, theoretically, if the windows, door and roof were removed, "It could eventually be pushed over, composted and a great place to plant crops like tomatoes," said Riseling. Ideally, the roof would also have been made of organic materials. "I had to compromise on the roof and use shingles," he noted. "I had a thatch roof material on order, but that fell through."

Depending on the structure and design, the initial cost of construction may be up to 20 percent more than using traditional building supplies. However, with its natural insulation and energy efficiency properties, it is estimated that the increased cost of construction is offset in energy savings over the lifetime of the home.

Building with straw bales

Straw is often thought of as a waste byproduct of the farm that, once used for bedding, is disposed of. However, straw is a viable option for building storage sheds, homes or commercial buildings.

Organizations like the California Straw Building Association (www.strawbuilding.org/sbweb) and companies like Harvest Homes, based in Canada (www.harvesthomes.ca), provide resources for those interested in using straw in construction.

There are two basic types of straw bale construction: load-bearing, also known as Nebraska style, and non-load-bearing construction. In load-bearing construction, the straw bales are stacked like bricks and support the structure's load (weight). When used in load-bearing construction, the bale supports the vertical load. High-density bales with proper compression eliminate the possibility that the bale will settle under the weight of the roof.

Non-load-bearing or infill constructions utilize independent structural systems where the straw bales fill in between.

Infill construction uses conventional techniques or can be engineered to meet building codes, which makes it easier to receive a building permit, since code officials consider straw an alternative insulation material. When using straw as an infill, it can also be less intimidating to builders who may not be familiar with using the material in construction.

North and west walls
of a small lime-plastered straw
bale home in California.

North and west walls of a small lime-plastered straw bale home in California.

As with conventional materials, quality is critical. The straw should be a golden color; a darker-colored bale suggests water damage and lower quality. A bale used in construction should also be dense and should maintain its shape when lifted by one string.

You can work with builders who are experienced in using straw bales during construction or attend workshops designed to teach beginners about using straw bales for structures, which will cover the basics of design as well as electrical and plumbing systems.

Interior view of a bale
raising in progress.

Interior view of a bale raising in progress.

Benefits of straw

Building with straw provides several benefits. Straw structures are energy-efficient, requiring less heating and cooling than traditional buildings. Since the walls are thicker, the straw acts as a sound barrier that absorbs and blocks noise that can easily filter through less dense materials.

Straw is also three times more fire-resistant than conventional homes. According to the website www.strawbale.com, "Canadian and U.S. materials laboratories have found that: 'The straw bale/mortar structure wall has proven to be exceptionally resistant to fire.' In these tests, the flames took more than two hours to penetrate the plastered bale walls. Conventional framing built to commercial standards took only 30 minutes to one hour to burn.

Straw bales being set into a post-and-beam framework,
typical of many bale buildings.

Straw bales being set into a post-and-beam framework, typical of many bale buildings.

Straw bale structures are also less attractive to termites and other insects that can plague a structure made of conventional building materials. On farms, livestock are fed hay, while straw is used for bedding because it has no nutritional value. Similarly for insects, straw provides little nutritional value and therefore is not an attractive option.

Using straw bales to build farm structures, be it a storage shed, barn or home, is a viable option. For farms producing straw bales, a majority of materials needed to complete the project will be readily available. Prior to beginning construction on any structure, check the local building codes.

Katie Navarra is a freelance contributor based in Clifton Park, N.Y., and writes about agriculture and the equine industry regularly.