Closed-loop Life Cycle Environmental Impacts of Buildings and Building Products

Environmental life cycle assessment (E-LCA) is a widely used and robust method for estimating the environmental impacts of building products over their life cycle. In high-performance buildings, the next opportunity for reducing environmental impacts lies in the embodied impacts: impacts from manufacturing building components and downstream activities and end-of-life. However, there is limited guidance on how to consider the life cycle of building components when they do not coincide with the life cycle of the building.

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During my doctorate, I performed closed-loop E-LCAs for different alternatives of building framing systems (see Figure below). Reusing steel frames has resulted in the lowest environmental impacts, but the reuse benefits depended on aggressive reuse rates (>70%) and multiple reuses. This work has also contributed to the E-LCA body of knowledge by showing that different E-LCA methodologies (i.e., process-based and hybrid E-LCA) generated conflicting results in a closed-loop assessment.

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Another gap in E-LCA when applied to CE strategies is the lack of consideration for material replacements and durability. Environmental impacts from replacing building products are often neglected in most studies of embodied carbon reduction in the built environment. Recently, I have applied E-LCA to compare the impacts of replacing building components with different durability. Not all materials with longer lifespans resulted in lower environmental impacts. For example, two replacements of steel roof resulted in higher embodied carbon than four replacements of a plastic alternative over the building’s lifecycle. The results showed the importance of considering future replacements when comparing different alternatives of building materials. Lastly, I collaborated with other researchers in Dr. Melissa Bilec’s team to conduct an E-LCA for alternative circular scenarios in an existing Living Building. The paper resulting from this effort is currently under production. According to our results, remanufacturing solar panels showed significantly higher potential than any other CE strategy included in the analysis.