Perlite Roof Insulation Perlite rigid mineral aggregate insulation board is composed of expanded perlite, cellulose binders, and waterproofing agents. Its tough top surface is treated to retain bitumen for a tight bond with the membrane. Available in 24" x 48" (.61m x 1.22m) and 48" x 48" (1.22m x 1.22m) boards. Koppers also offers tapered roof insulation. Contact your Koppers representative for information. To learn more about Perlite Roof Insulation, select from the following: Uses Benefits Standards & Compliance Limitations Storage Thermal Values Technical Data Maximum Flute Span  Return to Roof Insulation