I know cars at metal and metal gets cold so its not full proof if you're just insulating the windows. I have a 2006 Honda CRV that I camp in regularly thats converted for long term living if needed. I have cut window covers made out of poster board and reflectix, but it doesn't seem to do much to keep warm if camping in cold nights. I was wondering if something like wool or the R board from Home Depot / Lowes would actually help keep warm inside.