What types of insulation are recommended for Galvalume roofs? Are there any to be avoided?

By far, fiberglass roll insulation is the most commonly used insulation for Galvalume steel roofs on nonresidential buildings. It can be used in any of the available thicknesses to give the required insulation value. One of the main benefits of retrofitted Galvalume roofs installed over leaking nonmetallic flat roofs is the ability to add insulation under the new Galvalume roof and realize significant energy savings from reduced heating and cooling requirements. In such instances, fiberglass roll insulation can either be placed on top of the old nonmetallic roof or under the new retrofit roof. Wet insulation, which may be rain soaked at the site or wet from condensation or a leak in the roof, should not be in contact with Galvalume roof panels. Insulation should be dry when installed and kept dry after installation. Fiberglass insulation retains water and can cause rapid inside-out corrosion on Galvalume sheet panels. Also, spray-on insulation is sometimes used inside buildings under ...  more