"Pima County (along with the City of Tucson) has been much more open to permitting the use of alternative materials. This exhibit, arranged by the Pima County Building Department, was planned as an educational event to promote awareness of regionally available and appropriate alternatives to conventional, wood-based building products."

• Introduction
• The seminars
• The exhibit booths
• Conclusions
• Endnotes
• Author information
• Additional web resources

Introduction

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Architecture necessitates building materials and, as interest in sustainability grows, so does experimentation and innovation in the development of alternative building materials. When an email arrived announcing the first-ever Pima County Alternative Building Materials Exhibit in downtown Tucson, Arizona, on 21 April 2000, I was intrigued. The building market throughout the United States is largely dominated by wood construction. This fact is usually reflected in the building codes, either tacitly, by not having appropriate mechanisms in place for reasonable approval of alternative materials; or overtly, by greatly restricting or even banning the use of such materials. In contrast, Pima County (along with the City of Tucson) has been much more open to permitting the use of alternative materials (1). This exhibit, arranged by the Pima County Building Department, was planned as an educational event to promote awareness of regionally available and appropriate alternatives to conventional, wood-based building products. I decided to attend and report back to ALN readers on what I learned.

The exhibit crammed a wealth of information-gathering opportunities into nine hours, by means of seminars and exhibit booths. Some 27 vendors exhibited both traditional and commercially developed building products. Three seminars ran concurrently during every hour of the entire exhibit. In general, the exhibitors were also the seminar-givers. I decided to attend the overview, adobe/rammed earth, and straw bale seminars, then visit the exhibit booths.

The seminars

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The overview talk was given by Mr. David Eisenberg (2), well known for his advocacy of sustainable building techniques. Eisenberg reviewed several widely used building materials:

• Wood: Still the most commonly used building material in the US, accounting for about 90% of all new building construction. This holds true despite wood's many problems (such as its susceptibility to pests and fire, its vulnerability to rotting and warping, and increasing questions about the degree to which it can be sustainably harvested). In recent decades, many "engineered wood products," often made with waste or scrub wood, have been introduced. These in particular raise the issue of how such materials might be reused or recycled after the useful life of the building is over.
• Bamboo: This giant grass can be sustainably harvested and is part of a long-standing construction tradition in many tropical regions, as well as east Asian countries like Japan. However, bamboo is not commonly used for housing construction in the US, so was otherwise little touched on in this exhibit.
• Steel: Energy-intensive to produce, thus has high "embodied energy." Has great structural performance and can be indefinitely recycled with very little degradation or loss of quality. A good conductor of heat, so it can be thermally problematic for construction. It does not stand up well to fires.
• Concrete: Very strong in terms of compression, and durable, but vulnerable to seismic stress. The production of portland cement, a constituent of concrete, is energy-intensive.Also, it is not easy to reuse or recycle at present; recycling it is an energy-intensive proposition (3).
• Adobe: The major advantage here is the wide availability and low cost of the soil to make various types of adobe. However, like concrete, adobe and traditional earth structures are vulnerable to seismic stress.
• Straw bale: Where grain residues are common, the materials for this technique are readily available at low cost. A lot of experimentation is currently going on with straw bale construction in particular. For example, in Ciudad Obregón, Mexico, Bill and Athena Steen (4) have been experimenting with straw-clay block construction. These blocks are easier to work with than traditional bales, a bit more compressible, a bit better thermally, and incorporate more waste materials and less soil than traditional adobe mixtures.

Throughout his talk, Eisenberg stressed the need for the building industry and consumers alike to place more emphasis on the legacy of building materials--that is, their effects on the environment not just during the life of a building, but also during their own manufacture and after the useful life of a building is over. Currently, where building codes exist they typically focus merely on not harming the physical safety of the occupants of a building during its lifetime. This idea that "buildings should do no harm" should be expanded to include what happens before the building is constructed and after it is no longer used.

After Eisenberg's talk, I attended Paul McHenry's presentation on adobe as the quintessential global/local building material (5). McHenry's slides showed a rich diversity of adobe structures from around the world, and his accompanying talk combined both personal reminiscences from his long career and technical observations on the nature of adobe and regional aspects of its use. For example, in the US where building is largely regulated by building codes, those codes that allow adobe construction at all typically restrict its use to two stories at most (6). Yet, several of his slides of multi-story dwellings, typically in the Middle East, belied the need for this restriction. His slides of a 1972 trip to Iran showed that the adobes there are typically smaller than those traditionally used in the southwestern U.S. and Mexico. These smaller bricks lend themselves to the construction of barrel vaults and vaulted arches, a considerable advantage in regions where virtually no wood is available for making roof-supporting beams and lintels.

From Europe, McHenry showed slides of rammed earth structures both humble and aristocratic. Europe's cold and wet climate has led to such regional adaptations as the use of stone foundations to keep the earthen walls out of snow, and roofs with large overhangs to protect the tops of the walls - their most vulnerable point - from erosion. In South America, the Incas raised carved and decorated adobe walls atop stone foundations that were so intricately and tightly fit together as to withstand centuries of seismic events. Unfortunately, the adobe walls themselves are more susceptible to earthquakes, and this is one of the major problems to be overcome with adobe. Another problem is that, due to its very ubiquity and low cost, adobe has become associated with poverty in many areas, despite its many advantages.

The seminar on straw bale construction was given by Matts Myhrman and Judy Knox of Out On Bale (7), an organization that has been active in promoting the straw bale revival of recent years. Myhrman and Knox illustrated their comments with slides of straw-bale structures, both new and old, from around the world. For example, one current program they focused on is a UNDP project to build straw bale health clinics in Mongolia. Throughout their talk, Myhrman and Knox stressed that straw bale is a building technique that should be explored and promoted in any area where significant amounts of grain crop residues are available. Many types of straw are usable, including wheat, rice, rye, barley, and oats. Among the many environmental benefits of straw bale construction is the possible role of such construction as a viable mechanism for carbon sequestration (8). This is a role that definitely needs further testing and consideration.

Myhrman and Knox emphasized that the basic technology of straw-bale construction is well understood; what's needed now is lots of local experimentation, to make the technology accessible in a wide range of areas and with a wide range of materials. In fact, bales could potentially be made with materials other than spent grain. For example, various construction projects have used shredded paper bales. Elsewhere, straw bales are being used to construct vaulted roofs, sometimes with bamboo ribbing. Ancillary roof products, such as roof skin materials using recycled latex paints and cellulose-based roof insulation, are also being tested. In short, throughout their talk Myhrman and Knox strongly promoted the idea of extensive, grass-roots experimentation to refine and adapt this technique to local circumstances.

The exhibit booths

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Plenty of experimentation has been going on in the arena of commercially developed products too, as demonstrated by the products on exhibit. Unfortunately, I could not review all of the exhibits; so, for sheer lack of time, I left out exhibits of ancillary products like photovoltaics and of steel-based framing systems. The following notes are arranged in alphabetical order by product. The comments are based primarily on what I was told by the representative of each product, in some cases amplified by information from the product literature they gave me. I have made every attempt to be accurate, but these notes should not be taken as an official representation of any product by its manufacturer.

Blue Maxx (9)

• Type: "Insulated concrete form (ICF)," i.e. rigid exterior "sandwich" of expanded polystyrene insulation, with interior "filling" of reinforced, poured concrete grout.
• Comments: Thin plastic spacers are used to hold apart the polystyrene panels. This minimizes "thermal bridging" (that is, the ability of heat or cold to travel easily through the wall). These spacers are made of recycled plastic, but other components of the system are not recycled. This technology originated in Europe in about 1970. Buildings using this construction system are about twice as energy efficient, on average, as buildings constructed with conventional wood framing.

E-Crete (10)

• Type: Precast blocks made of autoclaved aerated concrete (AAC).
• Comments: AAC was developed in Sweden 70 years ago. It is well-known in Europe and in recent decades has become more widely used in Australia and Asia. During manufacture, aluminum powder is added to the concrete slurry, causing it to expand and become filled with tiny air bubbles. Once the slurry has hardened, the resulting slabs are cut and cured in an autoclave for 8-10 hours. This process results in a crystalline structure called "Tobermorite," identical to a naturally occurring mineral.The final product is inert, lightweight, and has high insulative, sound-control, and fire-resistant properties. What makes E-Crete different from other AAC products to date is that its manufacturers have obtained a US license to use high-silica mine tailings as up to 65% of the total mixture. Third-party tests of both mine tailings and AAC supplied by the company have so far shown no evidence of hazardous characteristics or of chemical properties that would pose a health risk. The company plans to continue with this testing. The company is currently building a production plant in Arizona that is expected to be online in summer 2000. This plant is being designed to recycle all materials, resulting in zero-emissions production.

ECO-Block (11)

• Type: ICF wall system.
• Comments: ECO-block is widely available throughout the United States. Like other ICF systems, it provides insulation and sound-proofing far superior to conventional wood-framed walls. In this case, its insulation values are typically about R-50, and its use can result in up to 50% savings on typical heating and cooling costs. ECO-Block uses high-plastic webs and connectors for spacing of the polystyrene panels; a large percentage of this plastic is made from recycled material.

Fi-Dobe (12)

• Type: Fi-Dobe stands for "Fibrous Adobe;" in this case, it means adobe blocks incorporating recycled paper.
• Comments: As the manufacturer indicates, fibrous adobe is not a new technique by any means; the "added value" here comes from its recycled paper content. Since up to 70% of the "waste" in US landfills is unrecycled newspaper, Fi-dobe clearly has the potential to provide a significant ecological benefit in terms of waste stream reduction. Furthermore, fibrous adobe has much better insulative qualities than traditional adobe. The Fi-Dobe company is located in Columbus, New Mexico and currently distributes its products largely on a local basis.

Intégra Wall System (13)

• Type: Post-tensioned, concrete block system with injected polyurethane foam insulation.
• Comments: Because of the tensioning system used, no grouting is required. The blocks, called "Superlite Blocks," are manufactured with less internal structure than conventional cinder blocks, thus reducing thermal transmission and allowing for injection of more insulation. The polyurethane insulating foam does not contain ozone-depleting chemicals. According to the exhibitor, the product, invented in Arizona, has been on the market for about 20 years.

KC Panels (14)

• Type: Structural Insulated Panels (SIPs) made of Oriented Strand Board (OSB) panels with injected polyurethane foam insulation.
• Comments: The general technology for producing SIPs was developed in the US about 50 years ago. All SIPs consist of an inner core of insulation material sandwiched between two skins of load carrying material; this technology is currently widely used throughout the US, Europe and Japan. Unlike many other SIPs, KC panels incorporate polyurethane foam insulation, which is more expensive to produce but provides better insulation, chemical resistance and fire resistance than other commonly used core materials. The KC Panel Company, located in Tucson, has been manufacturing its panels since 1994.

Omni Block (15)

• Type: Insulated masonry system consisting of stacked concrete blocks with rigid insulation inserts, sealed and waterproofed by proprietary surface bond which is the third component of the system.
• Comments: Omni Block, Inc. is marketed throughout the US. The inserts are non-toxic, as is the surface bond component of the three-part system. Currently, the company is conducting tests to evaluate the possibility of using recycled glass as a component of the block. They are also testing the use of fly ash instead of some of the portland cement in the concrete mixture. If successful, these modifications will further decrease the product's environmental impact and lower its embodied energy.

Rastra Block (16)

• Type: Variant of ICF wall system
• Comments: In the Rastra Block system, the rigid insulation forms are made of a material called "Thastyron," consisting of cement, water, and approximately 85% polystyrene (by volume). The polystyrene comes from recycled post-consumer waste. The openings in the forms are relatively small, so less concrete grout may be necessary than with other ICF systems. During manufacture of the Rastra blocks, all residues are immediately recycled into new blocks.

Tech Block (17)

• Type: Variant of ICF wall system.
• Comments: Tech Blocks are patented wall construction units made from water, cement, recycled polystyrene foam beads, and Oriented Strand Board (OSB).The polystyrene is reclaimed from other manufacturing processes. The OSB forms the inside wall surface of the house once construction is completed. Once grouted, the blocks are immediately ready for interior drywalling and exterior stuccoing, requiring no additional materials such as furring strips or wire mesh. This product is currently manufactured in Phoenix, Arizona, but the company is exploring the possibilities of licensing the technology for production elsewhere.

Conclusions

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By this time, my head was whirling. All of these materials provide an alternative to conventional wood construction and typically confer significant energy efficiency benefits during the life of a building. But how could I best compare them to each other, or to the traditional techniques I'd learned about in the seminars? Also, what about Eisenberg's plea to consider the legacy of building materials both during manufacture and after a building's useful life? I wanted a tool for comparison that would encompass all of these factors.

I found one such tool in the notion of "Life Cycle Analysis," a "cradle-to-grave" analysis that can lead to a better understanding of a material's true long-term costs (18). This concept is still very much being refined and developed as a practical tool, and is most often used to consider buildings as a whole system. However, I also found some documents on applying LCA to building materials in particular. In one such schema from the University of Michigan, building materials can be analyzed in terms of the following three phases:

• Pre-building (or "Manufacture") Phase which includes:
  • acquisition of raw materials
  • Production of final material
  • Packaging
  • Transportation to building site
• Features that can increase a material's sustainability during this phase include:
  • Steps taken to reduce pollution caused by manufacture of the product
  • Waste reduction measures used during production
  • Reduction of energy required to make the product
  • Use of natural materials (which generally are less polluting and contain less embodied energy)

• Building (or "Use") Phase, which includes:
  • Construction/installation of materials
  • Operation and maintenance costs during building's life
• Features that can increase sustainability during this phase include:
  • High energy efficiency of material (e.g. R-value or fuel efficiency)
  • Use of non-toxic materials
  • Use of materials with long life expectancy

• Post-building (or "Disposal") Phase, which covers what can be done with the building materials once the useful life of a building is over
• Features that can increase sustainability during this phase include:
  • Use of durable materials that can readily be reused in other buildings
  • Use of materials that can easily be separated from other building components and recycled into new products
  • Use of materials that readily biodegrade without producing any hazardous substances as they decompose

In the long run, evaluative tools such as LCA will probably be most useful to product manufacturers, as they work to design more sustainable products. However, in the meantime, such tools can help architects, builders and consumers begin to evaluate a product's sustainability and incorporate that information into their product decisions.

In order to compare products at all, however, they must first know what products are available - and that's where events like the Pima County Alternative Building Materials Exhibit come in. As an educational event, this exhibit was a complete success, and the organizers and participants alike deserve thanks for their efforts. I'm hoping for another email from the Pima County Building Department soon - this time announcing that the Pima County Alternative Materials Exhibit will become a yearly event.

Endnotes

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(1) Pima County and the City of Tucson have adopted joint building codes specifically for straw bale and for adobe and other earthen structures. An annotated copy of the Pima County/Tucson straw bale code is available at (http://www.azstarnet.com/~dcat/Pimacode.htm). A copy of the City of Tucson, Town of Marana and Pima County, Arizona Earthen Building Code is available at (http://www.naturalbuilder.com/cobcode.html).
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(2) David Eisenberg is the Director of the non-profit Development Center for Appropriate Technology (DCAT). DCAT supports the development and use of sustainable approaches to meeting human needs through the appropriate use of technology. A major DCAT focus is addressing the institutional and technical barriers to sustainable and restorative development and construction. DCAT's web site (http://azstarnet.com/~dcat/) houses a wealth of materials on straw bale construction in particular.
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(3) A 1993 article from the Environmental Building News, "Cement and Concrete: Environmental Considerations" (http://www.buildinggreen.com/features/cem/cementconc.html) looks at how these materials are made and reviews environmental considerations concerning their production, use and eventual disposal.
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(4) Athena and Bill Steen are co-authors of The Straw Bale House, a well-known sourcebook for straw bale building. Through their books and other publications, and through workshops held at their homestead in Canelo, Arizona, they promote the creation of simple, comfortable shelter using local and natural materials. The Canelo Project web site (http://www.caneloproject.com/) has a good article on their straw bale work in Ciudad Obregón, Mexico (http://www.caneloproject.com/pages/articles.html#officebldg). as well as photos of the work done there on the "Casas que Cantan" (http://www.caneloproject.com/pages/cqc.html) and the Sonoran Save the Children Federation office building (http://www.caneloproject.com/pages/stc.html).
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(5) Paul McHenry is the Managing Director of the Earth Building Foundation, Inc. (http://www.earthbuilding.com/), formerly the Earth Architecture Center International. He has more than 30 years of experience with adobe around the world. Please see Mr. McHenry's article in this issue of ALN for more adobe stories.
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(6) According to material from The Natural Builder (http://www.naturalbuilder.com), the New Mexico State Adobe Building Code of 1991 (http://www.naturalbuilder.com/nm%20adobe%20code.html) restricts buildings using "masonry of unburned clay units" to a two-story maximum. The City of Tucson, Town of Marana and Pima County, Arizona Earthen Building Code (http://www.naturalbuilder.com/cobcode.html) restricts earthen buildings to one story or 16 feet in height, unless the structure is designed by an engineer or architect and approved by building officials. The City of Boulder, Colorado, Adobe Code (http://www.naturalbuilder.com/Boulder%20adobe%20Code.html) imposes the same general restrictions as does the Tucson/Marana/Pima code.
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(7) Matts Myhrman and Judy Knox have been involved in experimenting with and promoting use of straw bale construction since 1989. More information on their activities, and a series of online articles about straw bale, are available from the Out on Bale web site (http://www.azstarnet.com/~dcat/outbale.htm). A closely related site, DAWN/Out on Bale by Mail, (http://www.greenbuilder.com/dawn/default.html), acts as an information resource center and mail order business.
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(8) Carbon sequestration is a strategy aimed at helping mitigate the effects of global climate change. It refers to the removal of carbon dioxide (CO2) from the atmosphere. This CO2 is then stored in 'carbon pools' such as forests (in temperate climates), soils (in arid climates) and, in this case, in buildings. David Eisenberg's "Comments in response to the White House Climate Change Conference Local Meeting [Tucson, Arizona, October 6, 1997]" (http://www.azstarnet.com/~dcat/climate.htm) provide more information on the possible usefulness of straw bale construction as a carbon sequestration technique and gives practical suggestions as to how such potential could be further researched and exploited.
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(9) For more information on Blue Maxx, contact:
AAB Building System Inc
840 Division Street
Cobourg, Ontario, Canada K9A 4J9
http://www.bluemaxxaab.com/client/aab/AAB_UW_MainEngine.nsf/web/Home+Page?OpenDocument.
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(10) The E-Crete Company does not currently have a web site. For more information on E-
Crete, contact:
E-Crete, LLC
6617 N. Scottsdale Rd., Ste. 203
Scottsdale, AZ 85250
USA
Tel.: 480-596-3819
Fax: 480-596-3952
Two other companies in the US (Hebel USA and Ytong Florida USA) manufacture autoclaved aerated concrete, but unlike E-Crete LLC, neither holds a license to incorporate mine tailings into their AAC mix.
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(11) For more information on ECO-Block, contact:
ECO-Block, LLC
P.O. Box 14814,
Ft. Lauderdale, Florida 33302
USA
Web: http://www.eco-block.com/.
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(12) Fi-dobe does not currently have a web site. For more information, contact:
Fi-Dobe
c/o David Pennington
P.O. Box 370
Columbus, New Mexico 88029
USA
Email (please use subject line "message for David Pennington"): klee@vtc.net
A similar product is called Papercrete. In fact, Papercrete representatives were scheduled to attend the Pima County Alternative Building Materials Exhibit but were unable to attend at the last minute. More information on their product is available from the Papercrete web site (http://www.papercretenews.com/).
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(13) The Buckley Rumford Company's web site for Rumford Stoves has more information on Intégra wall systems (http://www.rumford.com/Superlite.html).
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(14) For more information on KC Panels, contact:
KC PANELS, INC.
2110 E. 14th Street
Tucson, Arizona 85719
USA
kcp@kcpanels.com
Web: http://www.kcpanels.com/.
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(15) For more information on Omni Blocks, contact:
Omni Block
11259 East Via Linda #992
Scottsdale, AZ 85259
USA
Web: http://www.omniblock.com/.
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(16) Rastra Blocks are manufactured and marketed by several licensees world-wide, so no one contact address can be given. The easiest way to obtain further information is electronically:
Email: info@rastra.com
Web: http://www.rastra.com/.
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(17) For more information on Tech Blocks, contact:
Tech Block International, LLC
1315 East Gibson Lane, B-2
Phoenix, AZ 85034
USA
Web: http://www.techblock.com/.
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(18) I found several good documents on sustainable design and sustainable materials at the University of Michigan's Sustainable Architecture web page (http://www.umich.edu/~nppcpub/resources/compendia/architecture.html#sdes). The documents are available either as PDF files for free, or as paper documents for a small fee. The documents in the "Sustainable Building Materials Module" were particularly useful for their application of the principles of Life Cycle Analysis to building materials alone, as opposed to a built structure in its entirety. Another interesting online document I found is "Building Materials: What Makes a Product Green?" (http://www.buildinggreen.com/features/gp/green_products.html). This January 2000 online report from the Environmental Building News describes how EBN editors developed criteria for judging the appropriateness of building materials for inclusion in their "GreenSpec" Directory.
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