Straw bale construction provides affordable, efficient housing
Housing developers are experimenting with a variety of alternative building methods, including straw bale construction
Published October 1, 1998 | October 1998 issue
You probably remember the popular children's story about the three little pigs who built a house made of straw. The fable tells us how the big bad wolf came along and huffed and puffed and blew the house down.
Thank goodness modern straw bale construction techniques have a leg up on whatever method the three little pigs used. Current straw bale construction technology provides quality housing that is not only safe from the big, bad wolf, but also affordable and energy-efficient.
Across the Ninth Federal Reserve District, the shortage of affordable housing is a critical barrier to economic and community development. From urban areas to rural communities, creating affordable and attractive housing is an ongoing challenge that usually requires significant public- or private-sector subsidies.
To reduce dependence on such subsidies and create livable, affordable and energy-efficient homes, developers are experimenting with a variety of alternative building methods, including straw bale construction.
This issue of Community Dividendprofiles a project in Missoula, Mont., that used alternative construction technologies to build affordable housing. The project was the result of partnerships between not-for-profit developers, builders, banks, and community organizations.
This article discusses the partnerships that made this project possible, as well as the cost-saving construction and design techniques used. Since no project can succeed without funding, we also look at how the project was financed and review some of the valuable lessons learned by the developers.
In Missoula, Mont., the Northside Project
used straw bale construction and other energy-efficient techniques
to enhance the affordability of two new single family homes.
(Photo courtesy of the Center for Resourceful Building Technology,
The Northside Project
The Northside Project in Missoula used straw bale construction and other energy-efficient techniques to enhance the affordability of two new single-family homes.
Women's Opportunity and Resource Development (WORD), a non-profit affordable housing and economic development organization that targets low-income, single-income, and female-headed households, was the primary developer and project manager for the homes. WORD sought to demonstrate that straw bale construction can provide attractive and affordable homes that use energy-efficient design and construction techniques, meet building code standards, fit into historic neighborhoods, encourage home ownership by low- and single-income families, and can be financed through conventional means.
Ren Essene, housing director at WORD, said she hopes that "...when developers and others see how reasonable straw bale building is, they will raise the standard for housing production, resulting in quality, comfortable, affordable homes with reduced toxicity and lower environmental costs."
The Center for Resourceful Building Technology (CRBT), located in Missoula, provided technical assistance for the Northside Project. CRBT's mission is "to serve as both catalyst and facilitator in encouraging building technologies that realize a sustainable and efficient use of resources."
CRBT staff consulted with WORD regarding energy-efficient materials and technologies that could be incorporated into the design and construction of the homes, and provided information about suppliers of alternative building materials.
The first-floor walls of these two-story houses contain a combined total of 509 straw bales as insulation between a post and beam frame. The bale walls were finished with low-maintenance cement and fiber-cement stucco panels. Traditional fiberglass batts insulate the wood framed second-story of each home, and blown-in fiberglass insulates the roof.
These homes have traditional designs befitting the historic Northside neighborhood. Each includes 1,170 square feet of space with two bedrooms, one and a half baths, laundry facilities, a kitchen with a work island, and a combined living and dining area. The designs include window seats and built-in bookshelves, custom features typically not cost-effective for an affordable housing project. Since straw bale design creates wide wall expanses and deep windowsills that lend themselves to these amenities, value is added at no additional cost.
Other features of the homes include low windows that provide lots of light and vaulted ceilings on the second floor. These homes were built with natural gas space heaters on the main floor capable of heating the entire home, even in a Montana winter.
Despite several unanticipated factors, final construction costs came in on budget at approximately $63-65 per square foot. WORD and CRBT estimated that affordable houses in the Missoula market cost an average of $70 or more per square foot. According to Tracy Mumma of CRBT, "The use of straw bale construction did not make the project affordable, but instead added value to the homes without adding cost."
Adding value while maintaining affordability
In Missoula, designers and builders strove to balance construction costs with the goal of building low-maintenance homes that provide long-term affordability.
The houses were built with shallow frost-protected foundations, rather than basements, to save excavation costs. This method is substantially less expensive than slab-on-grade construction and has proven effective in northern climates.
The energy-efficient design and construction of the houses will also contribute to their long-term affordability.
Exterior materials, such as vinyl window frames, cement stucco walls, and front porches built from a recycled plastic and sawdust composite contribute to low maintenance costs and long-term affordability.
Finally, the houses are located close to downtown business districts, accessible to public transportation, and within established neighborhoods that minimized the costs of infrastructure development and will keep living costs, including the cost of transportation, low for the homeowner.
As is usually true of demonstration projects, the participants learned a number of valuable lessons.
WORD and CRBT would improve a few design elements to further enhance the affordability of future homes. These changes would include stacking the two bathrooms to decrease plumbing costs, using a lower-pitched roof to reduce costs for roofing materials and labor, and increasing the flexibility of the living space to meet the changing needs of a growing family.
Plenty of complications arise when using alternative building methods for the first time without adding too many untried, unique features that can add substantial expense and delay project completion. Instead of trying every new method on one project, the developer can always make improvements on subsequent projects but will not have that opportunity if all of the available money and resources are exhausted on the first house.
Labor is another crucial issue.
The developers emphasized the value of dependable labor as one of the most important lessons learned during construction of these homes.
A more detailed discussion of labor and job-training issues impacting these projects can be found in the sidebar "Labor lessons learned in straw bale projects."
The most noteworthy lesson illustrated by the project is that alternative construction methods can help reduce both construction and ongoing housing costs.
When asked if it was worth the extra effort to build the Northside homes using straw bale construction, Mumma of CRBT responded with a confident "yes." Mumma said the ongoing partnership between CRBT and WORD has led to other affordable construction projects in Missoula, not necessarily using straw bale construction but incorporating other affordable and energy-efficient aspects of the Northside Project.
Essene at WORD summed up the challenges that face affordable housing developers. "As non-profit developers, we need to think holistically about how to address all aspects of affordable housing construction," she said. "What kinds of sites are we selecting? What kind of labor are we using? What is the long-term affordability of the project? What is the long-term benefit to the community?" Through projects such as these, those questions are receiving thoughtful answers.
For more information
For more information on the two Missoula homes, please contact Ren Essene of WORD at (406) 543-3550 or Tracy Mumma of CRBT at (406) 549-7678 or access the CRBT website at www.crbt.org.