Stop in for a cup of coffee

Whats everyone using for sound deadener/insulation that doesnt cost an arm and a leg. I've seen something about what you can buy at the local home store, but looking for options. I need to get something in my car so my feet dont get so damn hot.
There’s a bubble wrap style foil insulation I’ve seen a lot of guys, particularly in the rat rod genre using. Home Depot sells it as does most other home improvement stores