2-1/2" - 4X8 THERMAX SHEATHING R-16 | DuPont™ Thermax™ Sheathing is a multipurpose, nonstructural, rigid board insulation that is quick and easy to install in a wide range of exposed and concealed cavity wall applications. It consists of a glass-fiber-infused polyisocyanurate foam core laminated between 1.0-mil smooth, reflective aluminum facers on both sides. The glass fiber reinforcement contributes to improved fire performance and dimensional stability. DuPont™ Thermax™ Brand insulation delivers wall performance you can count on. It’s ready to meet your toughest building challenges – both outside and inside the wall – with a robust ISO insulation product line and an R-value that’s proven consistent over time and a range of temperatures.