Session: Green Buildings I

Hybrid Life Cycle Assessment Model for Construction Processes: Focus on Commercial Buildings
Melissa M. Bilec,^*   University of Pittsburgh
Robert J. Ries,   University of Pittsburgh
H. Scott Matthews,   Carnegie Mellon University
Aurora L. Sharrard,   Carnegie Mellon University

The design and construction industries have an increasing interest in and responsibility for a building’s environmental impacts, which are considerable over a building’s entire life cycle (design, raw material extraction and processing, construction, use, and end-of-life). While some existing research has assumed that the impacts of the construction phase are negligible; others have indicated that life cycle assessment (LCA) tends to underestimate the environmental impacts associated with construction. Part of the reason previous assessment of the construction industry’s environmental impacts has not advanced is the construction industry’s lack of data.

This research qualitatively and quantitatively examined the environmental impacts due to the construction phase of commercial buildings located in the United States. The research, conducted using LCA, also focused on further understanding and developing hybrid LCA modeling. The created process-based hybrid LCA model for construction will be presented, along with life cycle inventory results of PM emissions, GWP, SOx, NOx, CO, Pb, non-methane VOCs, energy usage, and solid and liquid wastes. Life cycle impact assessment results will also be presented for two to three impact assessment methods.

Results indicate that when compared with the entire building life cycle, construction - including service sectors such as design and construction management - is as important as the other life cycle stages of materials and end-of-life scenarios. In terms of hybrid LCA modeling, the process based LCA proved to be effective in modeling the construction phase and allowed for efficiently combining process and input-output inventories. Including input-output results, especially construction service sectors, is critical in construction LCA modeling. One case study’s results demonstrated that services had the highest level of methane emissions and were a significant contributor to CO2 emissions. The results were reviewed to contextualize their significance and relationship to the United States Green Building Council’s Leadership in Energy and Environmental Design rating system and the United States Non-Road diesel regulations with recommendations for improving both items.

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