I have single pane windows and would like to insulate them. I was thinking I could put some rigid insulation over them as a shutter and then hinge it at the top. I could lift them in the day and hook them to the ceiling and lower them at night. This would provide added value because it would really block out the light at night, provide sound insulation, and will double as a place to pin drawings that the kids make. When I went to buy this rigid insulation, I read a flammability advisory for R Max. Then I checked a piece at home, and yes, it does burn. Owen Corning's Foamular F 150 seems to have a better rating, but the manufacture claims that you need some 15 minute wall covering over it. So I have some questions:
1) Is this a reasonable approach to insulating windows? Am I making a big mistake for reasons that I haven't thought of?
2) Is there an ideal material to use for this? Is the pink F 150 "good enough" for inside use? Are there better products?
3) Any other advice?