Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit Vs. Replacement, National Trust for Historic Preservation, 2012:
- Retrofit Measures Can Achieve Performance Results Comparable to New Replacement Windows. When the performance for each upgrade option is taken into account, this study shows that there are readily available retrofit measures that can achieve energy savings close to new, high performance replacement windows.
- Almost Every Retrofit Option Offers a Better Return on Investment than Replacement Windows. Findings from the cost analysis showed that new, high performance windows are by far the most expensive measure, costing at least double that of common retrofit options when considering materials, installation and general construction commonly required for an existing home. In all climate zones analyzed, cellular shades, interior storm panels and various exterior storm window configurations offer a higher average return on investment compared to new, efficient replacement windows.
- The Bottom Line. Retrofitting windows with high performance enhancements can result in substantial energy savings across a variety of climate zones. Selecting options that retain and retrofit existing windows are the most cost effective way to achieve these energy savings and to lower a home’s carbon footprint. Retrofits extend the life of existing windows, avoid production of new materials, reduce waste and preserve a home’s character. READ FULL STUDY