Life Cycle Assessment and Service Life Prediction A Case Study of Building Envelope Materials

Models of buildings in life cycle assessment (LCA) often use simple descriptions of operational energy, maintenance, and material replacement. The scope of many building LCAs is often limited and uses assumptions such as building lifetimes of 30 to 50years. In actuality, building lifetimes vary considerably, and scenarios using standard assumptions may have incorrect results. Assumptions concerning material replacement, repair, and maintenance should be deliberate and as realistic as possible. This research was initiated to demonstrate the importance of service life assumptions on building life cycle assessment results. Three roof types (built-up, thermoplastic membrane, and vegetated) and three wall forms (brick, aluminum, and wood siding) were analyzed. These materials were combined and modeled as nine distinct building envelopes. Five service life models were used to determine the service life of materials and systems. The analysis considered impacts related to material manufacturing, construction, operation, and maintenance. The Tool for the Reduction and Assessment of Chemical and other environmental Impacts global warming potential, atmospheric eco-toxicity, and atmospheric acidification impact assessment indicators were used. The analysis of the cumulative life cycle impact and life cycle impact per year found that life cycle impact was primarily dependent on the predicted frequency of major material replacement as well as differences in the frequency and intensity of prescribed maintenance. In some scenarios, the relative differences in the life cycle impact of the alternatives were dependent on the environmental indicator used.