Polyisocyanurate insulation is a rigid, closed cell, continuous foam board insulation. Closed cell foam is made of uniform cells that are “closed.” The “closed” cells are pressed together, so air and moisture are unable to get in between the cells or inside the foam. Rigid polyiso insulation board is sandwiched between two facers that can offer unique performance characteristics (see question 11 below) and provides top-of-class insulative properties. Among its other properties, polyiso has:

• The highest R-Value per inch of commonly used insulations.
• A moisture-resistant foam core.
• Compatibility with most solvents used in construction.
• Excellent dimensional stability.
• Excellent performance in fire tests for both roof and wall applications; polyiso meets the strict standard of both FM Class 1 Approvals (FM 4450/4470), UL 1256, CAN/ULC S126M and NFPA 285 testing.
• A CFC- and HCFC-free product with zero ozone depletion potential and negligible global warming potential.
• Recycled content in most products (see manufacturer for details).