USAFoam.com, Menards.com and HomeDepot.com are some good places to buy four-by-eight foam sheets. USAFoam.com offers polystyrene foam sheets in over 30 different thicknesses, ranging from 1 inch to 32 inches. Menards.com offers a range of Owens Cornering Foamular sheets and JM AP foil-covered foam sheets in different thicknesses.
HomeDepot.com offers just the Owens Cornering Formular 150 foam board in a 2-inch thickness, as of August 2015. All three sites offer online purchasing and home delivery. Menards and The Home depot also have a range of stores that a buyer can visit to collect his purchase in person. Each site has a store locator tool to help a buyer find his nearest store.