Engineering, Alternative Materials, and Sustainability

by Bruce King

exerpted in part from the forthcoming book
Alternative Construction - Contemporary Natural Building Methods
edited by Lynne Elizabeth and Cassandra Adams
John Wiley & Sons, 2000 -- reproduced with permission

The increasing popularity of the so-called alternative materials in the industrialized nations presents an engaging and worthy challenge to the structural engineering community. Schooled to work almost exclusively with the "Big Four" - concrete, masonry, steel, and wood - many engineers are reluctant, or overly cautious, about working with material they never read about in a textbook. This reluctance can reach ironic proportions as when, for example, an engineer freshly trained in America or Europe returns to his home in the Middle East or Africa, but is unwilling to work with the vernacular sun-dried brick (adobe) architecture that has been of his own culture for a millenium, and is still, generally, all that the local population can afford. Upwards of 30% of the world's population is estimated to live in earth (chiefly adobe) housing, yet there is astonishingly little mention, much less study, of earth construction in engineering literature or building codes.

In the 40,000 years or so that human beings have been erecting shelter, it has only been in the last 200 years that we have had anything but anecdotal knowledge; the success or failure of structures depended entirely on the experience, judgement, and intuition of builders. With the refined application of the scientific method and the emergence of professional architects and engineers, we have developed a detailed understanding of building materials, with increasing reliance on laboratory testing over field experience. In many ways that has served us well, making possible the far more creative, and large, buildings necessary to shelter, feed, and transport the exploding population. And the now-hallowed concept of the "independent laboratory test" has done a great deal to separate promotional, distorted, or outright false information from fact.

Engineering design of building structures requires a knowledge of site (soil, topography, and climate), engineering principles in general, and physical properties of the building materials. Applying for and receiving a building permit in a place like California (this author's home) requires that the engineer or architect demonstrate that an alternative method or material will have satisfactory properties of fire and seismic safety, durabilty, ventilation, and sanitation.

However, laboratory tests are expensive, so materials and systems with no financial backing (be it affluent individuals, commercial enterprises, trade associations, or government) tend to be undertested—and therefore dismissed by the modern building community. Because much of what we know about the various alternative materials is empirical or anecdotal knowledge, it seems worth examining the distinction between empirical field knowledge and "lab results". Anecdotal knowledge is simply "something that I heard"; both the quality of the information and reliability of the source can vary enormously. By contrast laboratory testing is (ideally) clearly and thoroughly presented, replicable, and untainted by commercial or promotional intent. This author, as a practicing engineer, has received a wealth of anecdotal information that met all the stated criteria for laboratory testing, and has conversely reviewed lab reports (from well-known, accredited labs) that were so poorly done as to be useless or even misleading. So the distinction blurs, and the building professional must exercise intelligent discretion in reviewing all information encountered. This point is made not to dismiss the huge value of laboratory knowledge, which may or may not come from a laboratory per se, nor to assign validity to many unfounded claims that do get made about alternative materials. Rather, it is to plainly admit that much of what we know about many alternative materials is empirical, but musn't be dismissed solely on that basis.

Almost by definition alternative materials are less known to the industry, less researched and documented, and generally perceived as unproven. However, a closer look reveals many examples that start to build that proof: thousand year old multistory adobes in the Middle East which can hardly be called non-durable, plastered straw-bale walls passing undamaged through intense fire and weather, and high performance concrete that uses radically little portland cement. To be sure, engineering design with relatively little background information can be unnerving to someone used to the mountains of available literature on steel, concrete, masonry, and wood, but neither is it "shooting in the dark"; there now exists a surprisingly large body of research and field evidence on which to draw. Nor is there as much liability exposure as there might appear to be; courts typically hold design professionals to the "standard of care" of the time, and in the late 1990's in the United States, almost any engineer working with these materials (with his or her homework done) is helping to establish that standard of care.

An inexorable trend in construction, as well as other industries, is toward sustainability—conducting business in a way that can be continued through many future generations,. As a practical matter, this already means making increasing use of waste material and energy, more carefully using virgin material and energy, and restraining or eliminating the release of pollutants into the ecosystem. The trend is driven by economics as much as environmental concerns, and the engineering community can and must rise to the challenge of finding ever more creative and efficient ways to utilize the materials and energy readily at hand. With the forests and cheap energy disappearing, the landfills filling, and the world's population swelling, we must very obviously become skilled at doing more with less. The structural engineering community must furthermore commit to supporting those very large and growing numbers of the Earth's population who desperately need any kind of useful shelter, but can afford only the earth, plant fiber, and waste materials near at hand. Otherwise, the many mission statements about protecting public safety and preserving life become hollow rhetoric, for we would then be merely servants of the affluent, blind to the often harmful effects of our sometimes obdurate intractability. It is this engineer's profound hope that his peers will bring their enormous intelligence and creativity to bear in establishing effective use of any and all resources available to shelter human beings in the coming millenium.