Did you know, you can use common bubble wrap as insulation for windows? I had heard of this bubble wrap trick to save energy before, but had never actually gotten around to trying it. Not for every window, but just an idea to consider.
DIY Survival Pantry: Advanced Prepper's Guide on How to Stockpile a 6 Month Supply of Food and Water! With Modern Tips and Hacks! (Canning and Preserving, Prepper Survival, Preppers Pantry) by Simon Charboneau