March 2014: Are Sustainable Structures Compactible with Common Sense?

The March 2014 Structural Forum column baffled me.  The author has not documented the basis of his assertion that “sustainable” buildings are only one percent better than “standard” buildings, nor did he explain why he “ignored the energy used to run buildings” even though, of the total energy used to construct and maintain a building over its lifetime, operation typically accounts for about half.  We are left with the somewhat self-congratulatory argument that anything an engineer touches is better than prior designs because of increased structural efficiencies;  or perhaps that what some call “sustainable” design really is not sustainable.

It’s been a couple of years since the last semi-credible “climate skeptic” examined the evidence and said that not only was he convinced, but things are worse than originally thought.  While public agencies are preparing for rising sea levels, more frequent droughts, etc., maybe we should examine the definition of “common sense” as well as “sustainable.”  Instead of designing an “efficient” new bridge to widen a highway, we could replace the highway with a mass transit system; instead of state-of-the-art and “efficient” McMansions, we could design multi-family housing with equally efficient structures, preferably using truly renewable materials.

We have enormous challenges ahead of us.  LEED won’t meet them in time; that does not mean we should abandon the goal of sustainability, but rather that we should reset our entire outlook on what we should build, and how.

Thor Matteson, S.E.
Berkeley, CA

Response from the Author

My admittedly outrageous statement that current “sustainable” structures are little different from normal structures is based on the following assumptions:

  • It is essential that engineers lead the way in reducing impact on the environment and depletion of non-renewable resources.  See Building for a Sustainable Future:  An Engineer’s Guide, published in February 2014 by the Institution of Structural Engineers.
  • My comments were limited to what engineers can do once the decision has been made to construct something; i.e., their normal job.
  • The energy used to operate buildings is not part of structural design; also, the end of a structure’s life and potential for recycling are not within the engineer’s control.
  • Structural engineering design codes, augmented by value engineering, generally result in near-minimum-weight and -cost structures.
  • For a typical large building, say 50,000 square feet, the choice is between steel and concrete frame, with similar floor structures.  Stripped to structure only – foundations, cores, columns, beams, floor slabs – there is virtually no difference, in terms of cost, weight and embodied energy, between steel and concrete options; rather, the differences are smaller than those that arise out of project-specific and commercial circumstances – the precise sources of construction materials, their transport to site, required speed of construction, preferences and experience of contractors, etc.  Many studies have demonstrated this.
  • The outcome of whole-life embodied energy calculations depends entirely on the assumed life of the structure, which is generally arbitrary; this always lies in the assumptions given in the small print of such calculations.

Bill Addis, Ph.D., MCIOB

Closure

Thanks to Mr. Addis for clarifying this, and for his other contributions toward sustainable design.  His first point, that engineers should lead the way in reducing environmental impacts, suggests that we need to shift our approach to his other five points by influencing the following:

  • Deciding what we construct – e.g., suburbs, exurbs, and freeways vs. well-planned, high-density housing areas with no need for private automobiles.
  • Using materials that result in lower operating energy – e.g., steel-framed houses with poor thermal performance vs. wood-framed.
  • Measuring on a “per need” basis, not a per square-foot basis – e.g., the couple who asked me to design a 5,000-square-foot retirement home, glowing about how energy-efficient it was, should have been guided toward a much smaller home or apartment.
  • Thinking beyond the structural core – e.g., can the structure be adapted to future uses, or can components be easily reused or recycled?
  • Designing for true resource efficiency, not just to meet artificial goals subject to redefinition for the convenience of the owner or design team.

Every building material sector tells you how theirs is the most sustainable to use.  The truth is, unless some 7 billion other people can build just the same way you are, and never reduce the supply of raw materials, your building is not sustainable.  The last time we practiced truly sustainable construction was before we started mining coal.  We don’t need to regress, but we definitely need to change course swiftly, while we still can.

Thor Matteson, S.E.

Berkeley, CA

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