Changing significance of embodied energy: A comparative study of material specifications and building energy sources

Despite the increasing significance of embodied impacts of buildings, efforts to reduce their environmental footprints have been concentrated on the operational impacts of buildings. This study investigates the changing significance of embodied carbon over the entire life cycle of whole buildings. A case study of an office building was modelled with Revit, and sensitivity analyses of the modelled building were performed by varying the material specification and energy use pattern for seven other typologies. Using Revit, BIMWASTE tool, ATHENA Impact Estimator and Green Building Studio, comparative life-cycle analyses were carried out for the eight building typologies. The study suggests that notwithstanding the enormous impacts of the operational stage on life-cycle carbon of fossil fuel-based buildings, embodied impacts could vary between 8.4% and 22.3%. A key determinant of the proportional impacts of embodied energy is the nature of materials used for building construction. Similarly, embodied impacts of buildings become more significant and could contribute up to 60% of their life cycle impacts as they become more energy-efficient during their operational stage. As the study confirms the varying significance of embodied energy as construction materials and energy use patterns change, it implies the need for policy measures based on a whole life assessment methodology, instead of the usual ways of giving sole importance to the operational impacts of buildings. With buildings becoming more energy-efficient during their operational stage, there is an urgent need for an increased focus on the embodied impacts of buildings, especially as renewable energy resources are becoming widely adopted.