I can remember a short 15 years ago, nearly at the start of my career as a structural engineer, when “sustainability” and “green design” were just becoming household terms in the building industry. Although it seems a bit laughable now, to many at the time, the idea that the environmental impact of a building’s design and construction would be a mandated consideration for future projects was truly a foreign concept.

Today, my perspective is that we are really only at the end of the beginning when it comes to building sustainably. Sustainable building design, or at least its most commonly used metric, the LEED Credit System, is still in its nascent stages; it is a growing, changing organism that has yet to reach a real state of maturation and begin to attain its aim of making a measurable impact in reducing, and even turning back, the building industry’s detrimental environmental effects at the global scale.

For those unfamiliar, the LEED system assigns “credits” to a building that contribute to an overall score representing the building project’s environmental impact with the goal of calling attention to and rewarding sustainable design decisions. The portion of the current LEED credit system score that structural engineers have the most direct ability to influence is under the Materials and Resources Credit Category. Current metrics for those resource credits are generally limited to specifying recycled content in structural materials and determining whether they were sourced locally and responsibly. These are good steps—steps which have caused the industry to react and change, but in practice, they tend to be prescriptive. They encourage very little engagement and innovation on the part of the structural engineer to shape more dynamic change.

On the horizon, however, and possibly as soon as the next version of LEED is released this year, a more sophisticated and powerful tool, lifecycle accounting, will begin to be at the disposal of designers and engineers within the LEED system, allowing us to directly measure and compare the environmental impact of common building materials through analysis of their production, usage and disposal.

Coca-Cola is credited as the first company to formulate a business decision about its product based on lifecycle accounting. In 1969, they were confronted with the decision to continue using glass bottles or change to plastic. Instead of using the simple metric of material “first-cost” – the cost of the materials in manufacturing – they pioneered a holistic study of the complete lifecycle cost of their soda containers. Even though plastic bottles were a more expensive petroleum-based material, they were the favored choice because they were made at the same plant as the soda; lighter weight, reducing overall transportation costs; less breakable; and at the time, easier to recycle.

Today, when you walk into a Tesco supermarket in London, you will find that labels on many of the products include a summary statement of their embodied carbon (the universal metric for measuring global warming potential), determined via lifecycle accounting methods. This is not a measure of the carbon contained within the product but rather, the total equivalent carbon released into the atmosphere during the extraction of the product’s raw materials and then through manufacturing, packaging and transporting it to store shelves. Tesco’s intent in labeling products this way is to encourage manufacturers to work toward reducing the environmental impacts of their products by giving the consumer the power of information and the choice to make the most environmentally responsible purchase.

Similarly, and unbeknownst to many, nearly two decades of global academic research has been occurring to collect an accurate inventory of data and develop the standards by which we can measure and declare a building product’s environmental impact. Locally here in Seattle, it is encouraging to note that groups such as the Carbon Leadership Forum, Consortium on Research for Renewable Industrial Materials (CORRIM), Architecture 2030, Preservation Green Lab and The International Living Future Institute have all been playing a part in the research, advocacy and application of carbon accounting in designing the built environment. The complexity and magnitude of the task can’t be underestimated. Thankfully, there are many dedicated hands laying the groundwork.

Embodied carbon

A breakdown of the embodied carbon for typical building elements shows that the superstructure accounts for up to 45% of the total. Sources: “Embodied CO2 of Structural Frames,” The Structural Engineer, May 2012; S.C. Kaethner BSc, CEng, MIStructE, Arup; J.A. Burridge MA, CEng, MIStructE, MICE, The Concrete Centre.

Studies show that the lion’s share of a typical, new commercial building’s embodied carbon is contained within its superstructure. With lifecycle accounting tools made available, it is the structural engineer who should be prepared to find him or herself thrust into the sustainability limelight. Structural engineers will be invaluable players at the design table, well-suited to play the role of carbon accountants. As the field advances in the coming years, on a project specific basis, engineers will be able to utilize in their work the structural materials (wood, steel, concrete, etc.) and systems (truss, moment frame, arch, etc.) which play the best roles in minimizing the building’s total embodied carbon and other environmental impacts.

Environmental impact and economic activity diagram

Figure 2. The objective of forthcoming sustainability requirements for building materials is to decouple resource use from economic growth while reducing the overall environmental impact. Source: CEN/TC 350—Sustainability of Construction Works

The highest-level aim of developing carbon accounting standards is to achieve resource efficiency in the built environment at a national scale. Structural engineers need to invest in and embrace the possibility of their important role. By use of their skills, imagination and influence at the design table, engineers can play an essential part in society’s future by ensuring that our resource use doesn’t continue to increase with our economic growth, while also decreasing the overall environmental impact of building. Isn’t it fantastic to imagine what sustainable design will look like in another 15 years?