Analyzing embodied energy and embodied water for university buildings using input-output-based hybrid method

Abstract

Buildings present a unique opportunity to not just effectively decrease global energy use but also drastically reduce nearly 40% of global carbon emissions to help mitigate the ongoing climate change. Although most of the building energy use is attributed to building operations as operational energy (OE), a portion of it is termed embodied energy (EE) that is consumed in building construction, transportation, and material production activities. EE of a building, therefore, includes energy consumed directly in onsite and offsite construction and transportation and indirectly through material consumption since each construction material consumes energy in its production and transportation. Like EE, buildings also consume significant amounts of fresh water directly and indirectly as embodied water (EW) in their construction, which is becoming a major concern globally. As fresh water is also depleted in producing and refining energy sources used as EE, a portion of this EW is attributed to energy-related water use (EREW). Most research so far has been focusing on the energy and carbon emission dimensions of buildings overlooking the equally important aspect of water use, which is also crucial for delivering a truly environmentally sustainable building. In this study, an input-output-based hybrid (IOH) model is created to compute and compare EE and EW of 10 higher education buildings and examine the correlation of the calculated EE and EW values. The results demonstrate that the total EE and electricity EE of the study buildings share a very strong positive correlation (r2 = 0.93-0.99) with the buildings’ total EW at the building level. This correlation, however, weakens at the material level. The share of EREW in the total EW ranges from 9-13%, which indicates that reducing just EE may not help decrease EW, and additional efforts may be needed to address EW and reduce fresh water use in building construction.