Tales of the green — sustainable lessons

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    In the silos of our projects, firms, and locales, surely there are moments of questioning the implications of the sustainability movement. Like Rostand’s Cyrano, sometimes the very methods used in pursuing a goal seem to prevent its attainment. In an effort to highlight similar situations of one step forward, two steps back, SEI’s Sustainability Committee shares some vignettes toward lessons learned and promoting sustainable practices.

    Ironic:

    • Concrete mix designs on projects that meet the minimum specified recycled cementitious material content can unintentionally increase the amount of Portland cement, even on a USGBC LEED Platinum project. The lesson? Identify maximum allowed cement content too!
    • An owner asked to have so-called alternative materials specified on a small medical building. Two significant items were autoclaved aerated concrete blocks for wall sills to reduce building energy consumption and recycled concrete aggregate for structural fills to increase material reuse. A lifecycle assessment (LCA) was also requested. In the excitement, the design advanced quickly, unfortunately, ahead of the LCA. In this particular case, the transportation phase weight in the LCA exceeded the gains in reductions from the materials. Lesson: Don’t delay the assessment, as it is similar to cost comparisons between different framing schemes.

    Shifted:

    • Adding the ISO 14001 environmental management system requirement was a recommended "best practice" to steel specifications, only to find out that the steel mills went away from this tagging after changes in the EPA program emphasis. While not exactly front page news, the reminder was that staying up-to-date is a constant process.
    • Used industry guidelines on recycled material contents, only to find out during construction procurement that products and materials with those specific recycled content levels are produced at a distance well over LEED’s 500 miles to the site, which obviates the local sourcing credit. The lesson was to consider the LEED checklist during the design of the project.

    "Engineers have a leading role in planning, designing, building and ensuring a sustainable future…"
    – ASCE Policy Statement 418, Adopted July 10, 2010


    Figure 1: Thermal break connection in progress.

    Discovered:

    • After conducting the structural design of an "innovative" mid-rise office building with many continuous, vertical, natural, open ventilation shafts running through the waffle slab floors, the project was followed by the renovation of a century old building that had basically the same shaft system in the masonry walls. However, the old shafts were being deconstructed to accommodate new ductwork. Lesson: Though sustainable changes come interspersed, we can still learn from the old.
    • On a $12 million mid-rise hotel, the use of discontinuous stainless steel fin plates to support brick shelf angles was announced by the construction manager in a Value Engineering meeting to be a staggering 50 percent more expensive. However, when asked, the CM offered that the amount was only $3,000. The stainless fins remained without discussion. Lesson: The project team should ask for specifics on cost-related items during the VE phase – it could save sustainable attributes and the owners’ dollars down the line.

    Confessed:

    • For a school cafeteria with ICF bearing walls supporting steel trusses, the Architect wanted exposed steel roof overhangs along the sides. To deal with thermal bridging, a design for an exterior steel column at each truss to carry the thermally isolated overhang framing was developed with the architect. The column was tied back to the wall at the top with stainless steel anchors. Problem solved! But the contractor proposed a "simpler detail" on the shop drawings that made the overhangs continuous with the main trusses. This more traditional arrangement was allowed by the reviewing engineer, who was not up-to-speed with the real design intent. Lesson: Explicitly identify thermal bridging mitigation concepts, and similar sustainable intentions, on the structural drawings.

    Collaborated:

    • On a humidity controlled exhibit space, roof overhangs were designed with thermally broken connections having fabric reinforced resin (FRR) plate inserts and stainless steel bolts. From observations in the field, it was clear that standard carbon steel bolts were used. Although stainless bolts had been submitted, they had not been shipped. The meeting over the issue was short. After merely indicating the difference in conductivity, the steel erector called the fabricator to demand immediate stainless bolt delivery. Lesson: Sharing intent can enlist a vigilant partner.

    Hopefully, your role in the advancement of sustainable practices will be enhanced through the commonality of experiences and lessons offered here. There are now projects committed to green, sustainable designs without a commitment to any accreditation program, suggesting that there may be a basic shift occurring in the practice. For further sustainable support, to do more with less, visit www.seisustainability.org


    "…We need to be really bothered once in a while. How long is it since you were really bothered? About something important, about something real?"
    – Ray Bradbury


    Russ Miller-Johnson, P.E., is with Engineering Ventures, PC in Burlington, VT. He serves on the SEI Sustainability Committee and is a member of the Vermont Green Building Network. He can be reached at russmj@engineeringventures.com.