Abstract: A composite panel is provided which comprises an organic foam core with layers of inorganic fibers on opposite major surfaces of the core. The fibrous layers are affixed to the core in a manner such that they are functionally integral therewith, thereby providing dimensional stability for the core. In a preferred embodiment, the panel is embodied in roof insulation which consists of a core of organic foam with a mat of inorganic fibers located on an upper surface of the foam core and a layer of inorganic fibers located on a lower surface of the core. The lower surface of the insulation is affixed to an underlying roof structure by a layer of adhesive and specifically asphalt. Alternate layers of asphalt and fibrous mats are applied over the upper mat of the inorganic fibers to complete the roof insulation system.