Product life cycle--Environmental aspects
Civil Engineering | Environmental Engineering
Purpose: Many life cycle assessment (LCA) studies do not adequately address the actual lifetime of buildings and building products, but rather assume a typical value. The goal of this study was to determine the impact of lifetime on residential building LCA results. Including accurate lifetime data into LCA allows a better understanding of a product’s environmental impact that would ultimately enhance the accuracy of LCA results.
Methods This study focuses on refining the U.S. residential building lifetime, as well as lifetime of interior renovation products that are commonly used as interior finishes in homes, to improve LCA results. Residential building lifetime data that presents existing trends in the U.S. was analyzed as part of the study. Existing data on product emissions were synthesized to form statistical distributions that were used instead of deterministic values. Product emissions data were used to calculate life cycle impacts of a residential model that was based on median U.S. residential home size. Results were compared to existing residential building LCA literature to determine the impact of using updated, statistical lifetime data. A Monte Carlo analysis was performed for uncertainty analysis. Sensitivity analysis results were used to identify hotspots within the LCA results.
Results and discussion Statistical analysis of U.S. residential building lifetime data indicate that average building lifetime is 61 years and has a linearly increasing trend. Interior renovation energy consumption of the residential model that was developed by using average U.S. conditions was found to have a mean of 220 GJ over the life cycle of the model. Ratio of interior renovation energy consumption to pre-use energy consumption, which includes embodied energy of materials, construction activities, and associated transportation was calculated to have a mean of 34% for regular homes and 22% for low-energy homes. Ratio of interior renovation to life cycle energy consumption of residential buildings was calculated to have a mean of 3.9% for regular homes and 7.6% for low-energy homes.
Conclusions Choosing an arbitrary lifetime for buildings and interior finishes, or excluding interior renovation impacts introduces a noteworthy amount of error into residential building LCA, especially as the relative importance of materials use increases due to growing number of low-energy buildings that have lower use phase impacts.
Aktas, Can B. and Bilec, M. M., "Impact of Lifetime on U.S. Residential Building LCA Results" (2012). Civil Engineering Faculty Publications. 4.
Aktas, C.B., Bilec, M.M. (2012). Impact of lifetime on U.S. residential building LCA results.” The International Journal of Life Cycle Assessment. 17(3): 337-349. doi: 10.1007/s11367-011-0363-x