subject: Study Shows Replacement Windows Are Best to Improve Home Energy Performance [print this page] Study Shows Replacement Windows Are Best to Improve Home Energy Performance
A study conducted by Ann Edminster used energy models of a single-family home to analyze how she could achieve the greatest impact on home energy efficiency at the most competitive cost. Ms. Edminster is a an architect and LEED Accredited Professional (AP). To determine how she could get the biggest bang for her buck, Ms. Edminster compared three possible energy efficiency improvements she could make to a home: the installation of high R-value replacement windows, improving overall insulation and installing a solar photovoltaic array. Based on this analysis she concluded that high R-value replacement windows generate the most cost-effective energy savings. The ModelMs. Edminster developed models for a suburban, detached, single-family home. She posed the question, "if I have a budget of $15,000 to spend on retrofitting a home to improve energy performance, what gives the biggest bang for the buck?" To answer this question she studied the outcomes attached investments of $15,000 into each of the following areas: 1. Increase overall efficiency: improve attic and under-floor insulation, carefully air-seal the enclosure, and exchange lighting and appliances to models that meet the ENERGY STAR requirements. 2. Replacement windows: replace all existing windows with R-5 windows. 3. Onsite solar power generation: install a 2-kW photovoltaic array on the roofA 1,900 square-foot home located in the San Francisco Bay Area was used as the baseline home. In order to ensure conservative results, she chose this mild climate where the benefits of energy efficiency improvements may be less drastic. For example solar panels would produce less energy in a location with fewer hours of sun. Edminster included two baseline scenarios for window replacement, one with single-pane, R-a windows and the second with double-pane, R-2 windows.ResultsIn both baseline scenarios one and two, the R-5 replacement windows yield the highest return on investment in terms of energy savings. In the baseline scenario with R-1 windows, the window replacement yields a 38.4% energy savings, and in the baseline scenario with R-2 windows, the window replacement yields 17.3% energy savings. Improving overall energy efficiency yielded between 12.4% and 15.8% savings, and solar panel installation generated between 12.1% and 16.2% savings. ConclusionEdminster summarizes her key findings saying that, "R-5-and-above windows represent a game-changing entry into the residential replacement window market and into the broader realm of energy efficiency retrofit options. While in the past, window replacement was not typically viewed as offering a good return on investment from an energy perspective (though often attractive for reasons of improved comfort), it should now be considered routinely for home energy retrofit projects."
