Investigation of exergy-based life cycle assessment of buildings

Life Cycle Assessment (LCA) started in the 1960’s to study environmental impacts of products, especially in comparative context. In the 21 century, LCA is even more relevant because it offers a life cycle thinking to global environmental problems such as global warming, ozone, and resource depletions. A building, as a product, contribute significantly to global environmental problems because of its generally extended life span, resource demands, and emissions during life span. The major challenges that limit the practical usefulness of studies on LCA of buildings are data intensity and availability, variation of units, subjectivity in weighting, and accuracy. Exergetic LCA is conceptually considered to be a more accurate and objective method to account for life cycle resource use. However, the full potential of exergy uses in LCA of buildings have not been explored. This research aims to investigate the extent to which LCA of buildings can be improved through the integration of exergy considerations. The science of cumulative exergy demand method is adapted to describe Exergy-based LCA (Exe-LCA) of buildings. The two basic adaptations of the method to LCA of buildings is energetic quality of life cycle resource use and energetic quality of life cycle emissions. The developed and validated method for Exe-LCA of buildings is applied to three case study on-campus buildings in comparison with their conventional LCAs. To overcome data availability and intensity issue, Autodesk Revit and a plugin, Tally are used as enabling tools to create digital models of the buildings and conduct conventional LCA respectively. The main findings are that the proposed method for Exe-LCA of buildings expresses the varying units of life cycle environmental impacts as a single objective unit to enable comparison of results between same-type buildings; reduces subjectivity by eliminating the need for normalization and weighting; and produces a more accurate and in-depth assessment than does the conventional LCA method. The method is encapsulated in an automated calculation tool, called ExeLCA, to make it more accessible for use by the building industry. It is demonstrated that Exe-LCA can improve the practical usefulness of LCA of buildings for a sustainable design and construction.