outer strip 29 can be rolled upon itself one or more turns defining a curl and providing the panel with a pair of strengthened outer rod like or tube like marginal ribs 30 the roll formed edge readily slides on the face of the rafter facilitating inserting the panel between adjacently disposed roof rafters if desired the panel can be anchored to the roof rafters by fasteners such as tacks staples or the like passing through adjacent and or straddling the rolled edge 30 the outer strip 29 can for example be disposed at an angle of approximately 45 degrees to the major portion of the sheet located between the according like pleated marginal portions 23 24 the pleating permits compressing the panel in a direction transverse to its length an amount sufficient to fit into the spacing between adjacently disposed trusses which as indicated above maybe about 1 inch less than the initial width of the panel before being inserted into position panel 20 has major transverse ribs 32 33 spaced inwardly a selected distance from respective opposite ends thereof and a plurality of secondary spaced apart ribs 35 disposed there between ribs 32 33 project upwardly toward the lower face of the roof sheeting and ribs 35 project downwardly the ribs stiffen the central major portion of the panel.