Abstract: A composite panel for use in the construction industry includes a core of foamed plastic material and a skin on at least one of its faces comprised of a two-ply material consisting of aluminum foil bonded to a mat of randomly oriented glass fibers into which the foam core has been expanded.The core material comprises the rection product of isocyanurate and polyester/polyether polyol with the isocyanurate in sufficient excess to form trimmer rings and to react with the polyol to form urethane linkages.Panels formed of the core material and the two-ply skins have excellent thermal insulation and fire retardant properties and the skins have excellent mechanical strength.