Evaluating the temporal representativeness of embodied energy data: A case study of higher education buildings

Abstract

According to the United Nations approximately 40–50% of the annual global energy supply is consumed by the building sector, which underscores the importance of reducing the energy consumption in buildings. A building’s life cycle energy consists of embodied and operating energy. Embodied energy (EE) is utilized in the processes of raw material extraction, manufacturing, transportation, repair, maintenance, and demolition, whereas operating energy in operating the building over its service life. EE calculations are heavily data-dependent and are, therefore, susceptible to issues related to data quality. Studies showed that the temporal representativeness of data is one such data quality that may significantly influence the accuracy of embodied energy calculations. In this study, we evaluated the temporal variations that occur over 5- and 10-year periods in the EE intensities at the material, direct and indirect EE, and building levels. These values were calculated using the input–output based hybrid models developed for the years 2002, 2007, and 2012. Results show a significant change in not just the magnitude but also the type of energy sources embedded in both direct and indirect EE components. Over the 10-year period analysed there is a 36% reduction in the total energy use and fossil fuels contribute to 76% of this reduction. The direct EE component increased from 14% in 2002 to 20% in 2012 for both our case study buildings. Results also indicate that the share of electricity in the total EE may be gradually increasing. The results further highlight the importance of using temporally representative data to ensure the high quality of EE calculations. Energy source specific EE results indicate that using outdated (10-year-old data) may overestimate the total EE for buildings by ca. 85%.