Framework for Environmental Analysis of Commercial Building Structures

To get a systematic assessment of a commercial building's environmental performance, the impacts that occur throughout the different stages of a product's life-cycle (raw materials acquisition and processing, manufacturing, use, operation, maintenance, and end-of-life) need to be identified and quantified. The environmental impacts that occur during the construction, maintenance, and end-of-life phases are not well known. Once those impacts are known along with the impacts from all building life-cycle stages, commercial building designs could be evaluated for their environmental impacts, areas or processes of significant impact could be targeted for improvements, and alternate building designs could be compared. This analysis is best performed using life-cycle assessment (LCA) which identifies each component of a system (all resource input streams and potential emission or waste sources), and applies mass-balance calculations (where inputs equal outputs) to them. This paper focuses on the construction processes for two of the most common building structure types for commercial construction: cast-in-place concrete (with steel reinforcement) and structural steel. A systems model of the critical processes involved with creating cast-in-place concrete and structural steel buildings is presented. For each activity within the process, necessary labor, material, equipment, and energy inputs as well as the ensuing wastes and environmental emissions are identified. The choice of study boundary, activity selection and detail, and direct vs. supply chain impacts are addressed. Process diagrams showing environmental impacts for cast-in-place concrete and structural steel are presented.