A Building Life-Cycle Embodied Performance Index—The Relationship between Embodied Energy, Embodied Carbon and Environmental Impact

Abstract

Knowledge and research tying the environmental impact and embodied energy together is a largely unexplored area in the building industry. The aim of this study is to investigate the practicality of using the ratio between embodied energy and embodied carbon to measure the building’s impact. This study is based on life-cycle assessment and proposes a new measure: life-cycle embodied performance (LCEP), in order to evaluate building performance. In this project, eight buildings located in the same climate zone with similar construction types are studied to test the proposed method. For each case, the embodied energy intensities and embodied carbon coefficients are calculated, and four environmental impact categories are quantified. The following observations can be drawn from the findings: (a) the ozone depletion potential could be used as an indicator to predict the value of LCEP; (b) the use of embodied energy and embodied carbon independently from each other could lead to incomplete assessments; and (c) the exterior wall system is a common significant factor influencing embodied energy and embodied carbon. The results lead to several conclusions: firstly, the proposed LCEP ratio, between embodied energy and embodied carbon, can serve as a genuine indicator of embodied performance. Secondly, environmental impact categories are not dependent on embodied energy, nor embodied carbon. Rather, they are proportional to LCEP. Lastly, among the different building materials studied, metal and concrete express the highest contribution towards embodied energy and embodied carbon.

Life Cycle Assessment (LCA) of Environmental and Energy Systems

“…Hu [12] proposed instead a new metric to describe the embodied environmental performance of buildings. This metric is named life cycle embodied performance (LCEP) and it is defined as the ratio between embodied energy and embodied carbon.…”

Cost and environmental impacts reduction through building compactness

“…The environmental impact of OE use is a well-established area of research and practice, with well-defined metrics, methodologies, building codes and regulations (Hu, 2020). Different authors argue that the better energy performance and efficiencies of the buildings have decreased the role of operating energy in a building's life cycle, compared to the EE, which plays an increasing role (Dixit et al , 2012; Dixit, 2019; Salehian et al , 2020).…”

“…Under Dixit (2019), optimizing operating energy is also easier and more streamlined than EE because of the complexity of EE calculation. For instance, while the percentage of EE varies about 50% in a typical single-family house (about 50% OE), the percentage increases up to 70% for low-energy buildings (energy-efficient buildings) or even more (100%) in net-zero energy buildings (Hu, 2020).…”

“…Dixit et al (2012) consider EE as a genuine indicator of greenhouse gas emissions because of its relationship to carbon emissions. However, although EE is closely related to carbon emission, they are not equal (Hu, 2020).…”

“…Different authors highlight the importance of the exterior wall and the structural system in the total amount of EE and CO 2 emissions (Salehian et al , 2020; Hu, 2020; Sposto and Paulsen, 2012 and Paulsen and Sposto, 2013). In a case study conducted in a Brazilian social housing project constructed with structural ceramic block masonry, it was found that almost 60% of the EE resulted from the materials used to build the walls (Sposto and Paulsen, 2012).…”