Ten tenets of structural sustainability


    So, you’ve come to the point where you want to incorporate sustainability into your structural engineering design practice, because you believe it is the right thing to do. Excellent; structural engineers can make a big difference in the sustainable features of a project. But where do you start? An alternative approach to focusing too much on rating systems such as the U.S. Green Building Council (USGBC) Leadership in Energy and Environmental Design (LEED) is to address the underlying sustainability issues.

    The following simple principles—or tenets—can help improve the sustainability of your structural practice. They are not rigid rules, but rather, a framework for developing your sense of sustainability for your projects, your workplace, and yourself.

    1. Develop an awareness of the environmental costs of construction materials and systems. All materials have positive and negative sustainability aspects:

    Concrete has great durability and strength, and lends itself well to crushing and reuse as sub-base material upon demolition. But, the worldwide production of Portland cement generates about 8 percent of the carbon dioxide that is emitted into the atmosphere.

    Steel has a high recycled content, and it is industry practice to reclaim structural steel during building demolition for recycling. However, steel requires significant energy for milling and rolling, and the market for scrap metal is strong, which increases the demand for virgin iron ore. Also, steel has high thermal conductivity, which should be considered when detailing building envelopes.

    Wood has low embodied energy, and is a renewable resource. But, some forests are unsustainably managed, and the use of recycled lumber is relatively rare, at present.

    2. Minimize the use of materials with high environmental impact. The challenge is to avoid compromising performance. For example, if the goal is to reduce the Portland cement in a project, fly ash can substitute for 20 percent or more for most applications, pound-for-pound, with minimal adverse affects and significant performance benefits.

    3. Consider the demolition, or deconstruction, of what you design. Bolted steel connections increase the likelihood of future deconstruction and reuse. Slabs on grade which are specified to be higher strength than required by performance require greater energy to break apart and crush.

    4. Strive for synergy of sustainability ideas with the rest of the team. Play the role of consultant! Increase your value by facilitating and working with other team members’ ideas. If the architect is looking for an exposed concrete soffit in lieu of ceilings, make sure the concrete finish is specified appropriately. Likewise, colored concrete slabs can be attractive, but crack control is critical. An even more proactive approach is to familiarize your self with the basic principles of sustainable design and understand how these mesh with the architectural design intent.

    5. Understand building envelope insulation requirements and coordinate with the team. Since the building envelope is usually part of the structure—or literally tied to it—structural engineers should understand the insulation system intended. For instance, a critical condition that requires careful structural detailing occurs at the slab on grade edge condition. In many climate zones, a certain R-value of insulation is required between the edge of the slab and the exterior, in order to prevent the large thermal mass of slab from equalizing heat with the outside.

    6. Understand resource-efficient M/E/P systems and coordinate with the team.
    Gaining advanced knowledge of the basics of geothermal heat pump systems, rooftop photovoltaic cells, greywater recycling systems, and the like can make the overall design process run smoothly, with fewer surprises down the road for everyone.

    7. Design buildings for adaptability and durability. Creating good buildings that will be used for decades is arguably the most sustainable thing that we can do. Make sure materials and systems are durable. If we can create flexibility for future use, we may be able to avoid premature obsolescence.

    8. Consider non-traditional structural systems. Some proven high-performance and low-impact structural systems have not yet been well accepted into mainstream construction, including the following:

    structural insulated panels (SIPs),
    insulated concrete forms (ICFs),
    shallow frost-protected foundations (SFPFs), and
    autoclave aerated concrete (AAC).

    9. Share the knowledge that you acquire of sustainable materials and systems with others. The Structural Engineering Institute’s Sustainability Committee will continue publishing articles of interest in the coming months. Many area groups, such as your local USGBC Chapter, have regular programs on topics of interest to design professionals. Discern the real benefits of products and systems from the claims of manufacturers and trade groups.

    10. Adopt sustainable practices in your business and personal life. We have many opportunities to make a difference, and lead by example. Consider more than simply the initial costs: Become an advocate for sustainable practices. In our own ways we can act as champions for a more sustainable world.

    James A. D’Aloisio, P.E., SECB, LEED-AP is a principal with Klepper, Hahn & Hyatt, located in Syracuse, N.Y. He is a member of the Board of the Upstate Chapter of the U.S. Green Building Council and a member of the ASCE Structural Engineering Institute’s Sustainability Committee. The committee website is www.seinstitute.org/committees/sustainable.cfm.