What is the unfaced PIR board (izoGRASS) and how does it differ from termPIR®?

“izoGRASS® are PIR boards cut to size, without facing — BOKKA's own production. They are used in covered/ballasted flat-roof build-ups (under bitumen felt, membrane, ballast). The lack of facing means reaction-to-fire class E and λD of about 0.027 W/(m·K). It is a different product from faced termPIR® — izoGRASS is not intended for ETICS systems or as a finishing layer.”