Life cycle assessment of materials and construction in commercial structures : variability and limitations

Life cycle assessment has become an important tool for determining the environmental impact of materials and products. It is also useful in analyzing the impact a structure has over the course of its life cycle. The International Organization of Standardization's 14040 series specifies how to perform a formal life cycle assessment in which the materials, construction, use, and demolition of a building are quantified into embodied energy and carbon dioxide equivalents, along with representation of resource consumption and released emissions. These results are useful to architects, structural engineers, contractors, and owners interested in predicting environmental impacts throughout a structure's life. Although many life cycle assessments have already been performed on various types of structures, most have occurred outside the United States. The life cycles of American buildings must be better understood before their environmental impact can be reduced. Regional variations also must be taken into account. Most existing studies have a variety of focuses, which makes them difficult to compare to one another, and they do not examine a wide enough range of buildings. This thesis quantifies the variability of building life cycle assessments by examining existing studies' differences and comparing them to a new study conducted using GaBi software. The new model assesses the carbon dioxide equivalents of one ton of structural steel, in three different forms, and one ton of reinforced concrete, in three different mixes. Impact assessment is performed using two widely accepted methods. The results from this thesis can be used to standardize and improve the study of typical commercial structures across different regions of the United States. Thesis Supervisor: John Ochsendorf Title: Associate Professor, Civil and Environmental Engineering and Architecture