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They actually came knocking...
Just in case you decide to do this again, put the foil on the outside to avoid stressing the seals around your glass with the extra reflected heat and light. Depending on how old your windows are, you could either end up losing the gas between panes or cracking the glass if there are extreme temperature differentials.
Had to do this when I was dirt poor in 2009, was a lot hotter when the window seals failed....