New windows are rated based on their energy performance during the use phase. This rating neglects the overall environmental impact caused by raw material extraction, manufacturing, maintenance and disposal. Due to the number of residential window replacements occurring today in the United States, there is a growing need to quantify the sustainability of window preservation as an alternative to window replacement. This study assessed the environmental impact of historic wood window restoration versus window replacement for the entire "cradle to grave" life cycle of the window assembly. This study focused on a typical, mid-twentieth century housing development in the Northeast United States using four window configurations as follows: 1. Restored original wood window with a new exterior aluminum storm window; 2. PVC replacement window; 3. Aluminum-clad wood replacement window; 4. Wood replacement window. The dissertation assessed the life cycle of window configurations using GaBi Software. The life cycle inventories were analyzed using the TRACI 2.1 impact method which translated the environmental consequences of the life cycle assessment processes into quantifiable environmental impacts. The dissertation also considered window thermal performance and life cycle costs. When considering life cycle environmental impacts, thermal performance, energy savings and material costs, the results indicated that wood window restoration was the best option when compared to replacement windows considered in this study; however, the results indicated that building service life and window service life assumptions could impact results. Thermal performance testing of windows revealed that window restoration techniques undertaken in this study improved the window's overall thermal performance. The testing also indicated that the effects of air infiltration had minimal influence on the performance of the restored window assembly when compared to a high performance replacement window. The results of the energy model exhibited only a small annual energy savings between the restored window assembly and a high performance replacement window. The payback cost analysis revealed that, while there was an immediate financial benefit of window replacement with the PVC option, window replacement frequency and overall life cycle environmental impacts would favor the restored window option. / Civil Engineering