Storm window
A second pane mounted over an existing window that adds insulation and cuts drafts for about a third the cost of replacement.
A storm window is an extra glass or acrylic panel installed on the inside or outside of your existing window. Modern low-e storm windows are permanently mounted, operable, and blend with the architecture — not the old seasonal panels you swapped out by hand. The Department of Energy notes they deliver energy savings similar to a full window replacement at about one-third the cost, can cut a home's overall air leakage by 10% or more, and reduce both drafts and outside noise. For homeowners with sound original or single-pane windows, storms are often the smarter spend than tearing the windows out. Compare the options in [are replacement windows worth it](/guides/are-replacement-windows-worth-it).