A panel assembly that includes a first panel having an inner surface and an outer surface, and a second panel having an inner surface and an outer surface. The second panel includes a plurality of rib members formed therein that extend inwardly. The rib members include an inner surface and an outer surface. A plurality of panel portions are defined between the plurality of rib members. The panel portions include an inner surface and an outer surface. The inner surface of the rib members are secured to the inner surface of the first panel, and the inner surface of the panel portions is spaced apart from the inner surface of the first panel to define at least first and second cavities.