Life cycle energy and environmental benefits of novel design-for-deconstruction structural systems in steel buildings

Design for Deconstruction (DfD) is a design approach that enables reuse of durable building components, including structural materials, across multiple building projects. An important DfD strategy is the use of pre-fabricated modular building assemblies and reversible connections, in contrast to cast-in-place composite systems that must be demolished at building end-of-life. In this paper we evaluate a novel DfD flooring system consisting of pre-cast concrete planks and clamped connections. Life cycle energy and environmental benefits of using this DfD system are evaluated using life cycle assessment (LCA) across four impact categories of interest to the building and construction sector including fossil fuel use, greenhouse gas emissions, respiratory effects, and photochemical smog formation. Eight different DfD building designs are tested for 0-3 reuses compared with a traditional structural design, with energy and environmental benefits accruing from substitution of avoided structural materials. Designs reflect expected loads and current code requirements, while the additional time required for deconstruction of DfD buildings is accounted for in the construction schedules. Monte Carlo simulation is used to generate 95% confidence intervals for the results. In general, DfD designs result in higher initial (original building) energy use and environmental impacts, but have statistically lower impacts than traditional designs if flooring planks are used at least once. Reusing planks three times as designed decreases impacts by a mean value of of 60-70%, depending on the building configuration and impact category. Energy use and environmental impacts from eventual recycling and/or disposal of the reusable components are significant, and emphasize the relative benefits of reuse over recycling.