Comparative review of assessment methodologies of building embodied energy

According to a report of UNEP, the building sector accounts for 40 percent of the total energy consumption in the world and is related with 33 percent of global greenhouse gas (GHG) emissions. During the whole life cycle of a building, the total energy consumption can be classified in two categories: embodied energy and operational energy. Operational energy means the energy consumed by a building to support its operation and maintenance; while the embodied energy is defined as the energy consumed in producing of a building, including the building material production, on-site delivery, and construction. Plenty of efforts have been devoted into the reduction of the energy consumption through the operational phase, however, there is a controversial about the evaluation methodology of embodied energy due to the lack of regulation or uniform standard. Currently, there are three prevailing methodologies to assess the building embodied energy: Process analysis, Output-Input analysis, and Hybrid analysis. The measurement procedure, requirement of database, system boundary, labour and time input as well as the evaluation result are all different. The evaluators need to select the suitable methodology to achieve their evaluation objectives. With the aim to give out a reference for the selection of methodology, a comparative review is conducted to compare the advantages, disadvantages, and feasibilities of the three methodologies; and the appropriate methods for different regions in the world are also pointed out.