PIR / Rigid Board Insulation
Polyisocyanurate (PIR) rigid foam boards are high-performance insulation products (thermal conductivity λ ~0.022 W/mK) used in roofs, floors, and cavity walls. Common brands include Celotex, Kingspan, and Recticel. The high performance means thinner boards are needed to achieve required U-values compared with mineral wool, making PIR popular where space is limited.