Abstract: An industrial oven for heating products therein of the type having four insulated side walls, an insulated top, and also a bottom which together define an interior heating chamber. Each of the walls has an inner skin and an outer skin spaced apart from one another, and further has insulation material between those skins. A structural steel framework supports and is located between the skins, and the inner skin is of a generally vertically corrugated sheet metal. Means are provided between the skins for holding the insulation material against the inner skin and spaced from the outer skin to thereby provide an air space between the insulating material and the interior surface of the outer skin.