This paper investigates and compares the electromagnetic behavior of different shielding enclosures built with composite panels (dielectric materials with conducting inclusions, carbon-fiber, fiberglass, conductive materials). The numerical model is based on a full wave finite element method taking into account the geometrical details of the walls and avoiding the use of the classical equivalent layer approach. A 2D composite enclosure with two wall structures is modeled: fiber rods shielding and metal screen shielding. Impacts of conductivity and rod diameter on the shielding effect are investigated. Concerning metal screen, the shielding effectiveness is studied for different metals with the same mass, leading to identify the most effective metal. The influence of the angle of incidence and the number of apertures is also studied. Finally, a comparison is performed considering the same mass of the two composite wall structures, each composed of fiberglass and carbon fiber.