Hello, what have we here? I think these must be the original storm windows from the Little Blue House. We must try them out. My husband discovered them in the falling-down cabin on our property, along with a couple more in the other cabin (now woodshed).
They say that a vintage window combined with a storm window is at least equivalent to a double-paned window, in terms of energy efficiency. Plus , these windows have loads of character. Here's yet another project!