Window insulation question

[Charles in SC]

I left the windows in when I did my bus and for the last 5 years I had some silver insulation stuff velcroed to the inside. It was getting old looking and kept falling off so last fall I had the windows covered with frosted tint. I did not realize how much insulation quality the silver stuff had. Is there something I could maybe paint on or whatever to insulate the windows?
Thanks in advance.

[gus]

I have the same setup. Insulating those old single pane windows is pretty hard to do and make it look decent.

Most stuff you try to tack on inside looks pretty bad.

I have installed night shades which do a fair job but if I had it to do over I would install the cellular insulating shades instead. They cost quite a bit more but now I know it would have been worth the money.

[H3Jim]

I left the window frames in and just replaced the glass with fiberglass.  It was the same thickness as the glass.  paintable, 2" insulation on the inside.