Steel doors with louvers Steel doors can be provided with a variety of louver designs and sizes. Material: 1.5 mm gi frame and 1.5 mm blades. Louver size 600 mm x 250 mm (for door size 1200mm x 2400 mm) Function – louvers permit free air passage, controlling the volume by their size or design. They diffuse or control direction of air flow by blade design. Louver type: split ‘y’ blades Louver construction the louver blades are welded to the frame and the entire assembly is generally fastened to the door with moldings. Generally, one molding will be an integral part of the louver, while the other molding will be detachable.