Reducing Environmental Impact of Buildings Based on Actual Building Analyses: A Multi-Criteria Study of Frame and Finish Materials

The building sector has a significant environmental impact throughout the life cycle of a building. Reducing the environmental load of the building sector is essential for creating a sustainable society. Many current reports focus on carbon emission, while other environmental impacts remain insufficiently evaluated. Furthermore, buildings serve different functions depending on the region, and the types and quantities of primary materials used vary accordingly. Under these circumstances, little research has focused specifically on Japan. This study conducted a life cycle assessment (LCA) covering the life cycle of material inputs (structural and finishing materials) for 95 buildings in Japan. In addition to greenhouse gas emissions, multi-criteria analysis, including characterization and integration (characterization such as acidification, ozone layer destruction, and photochemical ozone; damage assessment; and integration using LIME2 and LIME3), was conducted. Based on analyses of numerous buildings, the objectives were to clarify trends in environmental impact emissions by building use, conduct an environmental impact analysis that could serve as a future benchmark, and discuss for reducing these environmental impacts. First, the analysis of trends such as maximum, median, and minimum values across six building types revealed that the environmental impact per square meter tended to be lower for production and logistics facilities and higher for offices, government buildings, schools, hospitals, hotels, and condominiums across many indicators. However, significant variations were observed between individual buildings within each category. These results can serve as a benchmark for the environmental impact of future buildings in Japan. Next, GHG emissions and integration (LIME2, LIME3) were quantitatively identified for materials with high emissions, and the factors were considered. Furthermore, processes with high environmental impacts associated with the material were analyzed and identified. Ready-mixed concrete, reinforcing bars, and steel frames showed high values across quantitative indicators, whereas wood and other materials varied by indicator. Finally, based on these findings, perspectives for reducing the environmental impact of key materials are proposed for each stakeholder group.