Are inexpensive aluminum storm windows a good option?
Exterior storm windows are a good solution, and if they are installed correctly will give a better R-value than double insulated glass. They are also better for historic buildings because they do not require removing historic windows. Exposed metal might not look so good, but a coat of paint can often make them blend in better if anodized aluminum trim is not available. Interior storm windows are not a good idea because they can cause serious moisture problems on the windows.
