Exergy-Based Greenhouse Gas Metric of Buildings

To effectively reduce the greenhouse gas emissions in buildings, there is a need for a robust basis for measuring greenhouse gas emissions associated with the built environment. The conventional method to measure greenhouse gas emissions is based on global warming potential. However, global warming potential depends on erratic factors such as timeframe, location, and absorption rate, which, in turn, leads to unreliable metrics for greenhouse gas emissions.This study proposed an exergy-based metric to measure greenhouse gas emissions to eliminate the weakness. The proposed metric was developed using the cumulative exergy demand method based on standard chemical exergy of substances and is applied to a case study building. The major findings indicated that the exergy-based greenhouse gas metric is more robust and consistent than the conventional global warming potential (GWP)-based metric by eliminating the erratic factors, providing absolute values, obtaining a single objective function for environmental impact potential, and enabling indexing of values to assess environmental sustainability. This research explored the development of a metric based on analysis of energy quality for a robust, consistent, and comparative measurement of the environmental impacts of greenhouse gases emitted during an assumed life cycle (75 years) of a building. The results showed that an objective comparative value of the environmental impact of a building and/or its products can be obtained by unit mass/weight value if the energy demand data are unknown and by absolute mass/weight if the energy demand data are known. In any case, the environmental impacts between buildings or building products can objectively be compared. Practitioners can utilize the method or its results in indexing or benchmarking buildings for building environmental sustainability ratings using units such as per life span, area, and occupants. Standardized indices can be developed into a computer-aided tool for policy making and regulation of both existing and new buildings in terms of their environmental sustainability. The current global awareness about climate change and the environmental impact of human activities on the ecosystem makes this study even more relevant.