A rectangular framework for a module for an air handling unit includes eight longitudinally extending structural elements (18) interconnected by eight one-piece corner connectors (16). Each of the longitudinally extending structural elements has a predetermined length, which may be different depending upon the size of the rectangular framework. Each of the elements includes a hollow extrusion formed from a metal material. The metal extrusion (26) defines an outer surface and an interior having open ends, which have a predetermined shape. A hollow extrusion (28) formed from a plastic material defines an interior cross-section having an interior surface which is configured to receive the metal extrusion therein with the outer surface of the metal extrusion in confronting relation with the inner surface of the plastic extrusion. The corner connectors are formed from a non-corrosive structural material.