Abstract: Apparatus for molding rigid foam components of semicircular cross section suitable for insulating pipes and the like. A female molding component is formed of sheet metal material supported by a plurality of spaced, rigid crossmembers. This female component supports a top panel, the underside of which, in turn, supports a male mold component the semicylindrical surface of which is formed of sheet metal material which is supported by a plurality of spaced, semicircular rigid support members. When the mold is charged with an expansible foam, the pressure thereof serves to maintain the integrity of the mold profile. The design of the mold permits its fabrication utilizing relatively inexpensive material thus permitting the formation of rigid insulative foam segments at desirable unit cost levels.