Exergy-Based Life Cycle Assessment of Buildings: Case Studies

Martin Nwodo,Chimay J Anumba

doi:10.3390/su132111682

Abstract

The relevance of exergy to the life cycle assessment (LCA) of buildings has been studied regarding its potential to solve certain challenges in LCA, such as the characterization and valuation, accuracy of resource use, and interpretation and comparison of results. However, this potential has not been properly investigated using case studies. This study develops an exergy-based LCA method and applies it to three case-study buildings to explore its benefits. The results provide evidence that the theoretical benefits of exergy-based LCA as against a conventional LCA can be achieved. These include characterization and valuation benefits, accuracy, and enabling the comparison of environmental impacts. With the results of the exergy-based LCA method in standard metrics, there is now a mechanism for the competitive benchmarking of building sustainability assessments. It is concluded that the exergy-based life cycle assessment method has the potential to solve the characterization and valuation problems in the conventional life-cycle assessment of buildings, with local and global significance.

Highlights

The construction and operation of buildings together contribute to 36% of the world’s energy end-use and close to 40% of energy-related carbon dioxide emissions [1]
A table of values for the material exergy demand of the individual main building materials for the three case study buildings can be found in Appendices A–C
The application of an exergy-based Life cycle assessment (LCA) method to case-study buildings showed that its theoretical benefits compared to a conventional LCA can be achieved, such as enabling an easier comparison of LCA results between buildings through unifying units, more accurate measurement of energy demand by accounting for energy quality, a more in-depth assessment of resource depletion over a building’s life cycle, and solving the problem of characterization in LCA and, thereby, eliminating subjectivity in valuation

Summary

Introduction

The construction and operation of buildings together contribute to 36% of the world’s energy end-use and close to 40% of energy-related carbon dioxide emissions [1]. Life cycle assessment (LCA) ascertains the resource inputs and outputs into and out of a product (in this case, a building) system and the potential environmental impacts thereof. There are challenges when performing a building LCA that limit the realization of its full benefits. The conventional building LCA faces methodological challenges such as the inconsistency in functional units, the difficulty of system boundary definition, choice of allocation method, and accuracy of data sourcing [4]. Major challenges faced in the practical use of the conventional LCA method to assess buildings include, but are not limited to, the difficulty of identifying areas for improvement, subjectivity in results interpretation, and the difficulty when comparing results [5].

Results

Discussion

Conclusion