Influence of climate on the environmental and economic life cycle assessments of window options in the United States

• Life cycle impact assessment and costing were used to analyze windows.
• Extreme climates saw significantly larger energy savings from retrofitting windows.
• Low-solar gain windows were best environmentally due to electricity reductions.
• Each climate had a window choice which had a payback period of 10 years or less.
• Retrofitting Atlanta's windows would reduce CO2 emissions by 0.5 MMT a year.

Life cycle assessments (LCA) of building materials often exclude the use phase due to variability in buildings and difficulties in isolating energy use for specific components of a building. For this study, a basic single-pane window was selected as a baseline to compare to two basic double-pane windows and four energy-efficient windows in a single-family home. Seventeen United States cities were investigated to represent 17 climate regions. Using energy simulations, along with life cycle inventory and economic data for windows, a cradle-to-grave LCA and life cycle cost (LCC) analysis were conducted. Environmental and economic impacts are normalized and weighted to identify the best overall performing windows. Environmentally, the low-solar gain windows always performed best due to the reduction in electricity needs, whereas economically they performed best in warmer climates but high-solar gain windows performed best in cooler climates. Thirteen of the seventeen cities had window options with a payback period less than five years when all retrofitting option were compared. When projecting the impacts of retrofitting a large number of homes, it was found that metro Atlanta could reduce CO2 emissions by about a half a million metric tons of CO2 annually with any of the energy efficient window choices.

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