Window of opportunity: Save energy AND money with this upgrade


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There is a world full of energy-saving options out there, and our job is to choose as many as possible that we can apply to our daily lives. Upgrading existing windows with retrofit options is a great way to save energy and money, according to a new study.

The report, "Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit and Replacement," found that upgrading windows — specifically older, single-pane models — with exterior storm windows and insulating shades can result in substantial energy savings across a variety of climate zones.

The study was commissioned by the Preservation Green Lab and funded by the National Park Service's National Center for Preservation Technology and Training.

Analyzing decades of research about the performance of double-hung windows, the study compared the relative energy, carbon and cost savings of various choices in multiple cities across the United States.

"A number of existing window retrofit strategies come very close to delivering the energy benefits of high-performance replacement windows — at a fraction of the cost," said Mark Huppert, technical director of the Preservation Green Lab. "From weather stripping and sealing to installing exterior storm windows or interior cellular shades, almost every retrofit option offers a better return on investment than outright replacement."

The key findings are:

  • Retrofit measures can achieve results that compare with new replacement windows. The study found that retrofitting can offer energy savings close to new, high-performance replacement windows.
  • Almost every retrofit option offers a better return on investment than replacement windows. New, high-performance windows are the most expensive option, costing at least double that of retrofit options when considering materials, installation and general construction. Cellular shades, interior storm panels and exterior storm window configurations offer a higher average return on investment compared with new, efficient replacement windows.
  • Retrofitting windows with high-performance enhancements can offer energy savings across a number of climate zones. Choosing options that retain and retrofit existing windows are the most cost-effective way 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.


"Homeowners and designers who want to upgrade existing windows have many choices: from simple, low-cost, do-it-yourself solutions to complete replacement, which can cost tens of thousands of dollars," said David Brown, EVP and chief preservation officer of the National Trust for Historic Preservation. "This report provides the context and data to help budget conscious consumers make sound decisions."

Click here for the full report.