>>7246120Not him, but most people use Extruded polystyrene foam, available at hardware stores like Home depot.
https://www.homedepot.com/p/Owens-Corning-FOAMULAR-150-2-in-x-4-ft-x-8-ft-R-10-Scored-Squared-Edge-Rigid-Foam-Board-Insulation-Sheathing-45W/100320352Not to be confused with Expanded Polystyrene, AKA the white foam thats used for protection when shipping stuff out in the mail or in packages for corners. While you can use Expanded Polystyrene, it's not as dense as the extruded version, and can crumble unless your going to put some protective layers over it.
