Polyisocyanurate, commonly called polyiso, is a high-performance, rigid foam insulation widely used in construction for its excellent thermal resistance and fire protection. It's often used in roofs and walls, both in commercial and residential applications. https://www.quora.com/profile/Vofip69168/On-Polyisocyanurate-A-Modern-Solution-for-Smarter-Insulation-In-the-landscape-of-modern-construction-and-energy-effici