Abstract: A secondary roof system for application over existing metal roofs of the cleat panel or structural panel type. Elongated expanded polystyrene insulation panels are inserted in the roof pans of the existing metal panel roof. A plurality of interlocked secondary metal roof panels having the same width as the original roof panels is disposed over the insulation panels and the interlocking edges attached to the upwardly projecting joints of the existing metal roof panels. A small dead airspace may be provided between the secondary panel faces and the upper faces of the insulation panels.