Knauf Rockwool is a high-performance stone wool insulation primarily used for thermal, acoustic, and fire protection in buildings. In roofing applications—especially flat roofs—it is typically installed as rigid boards beneath a waterproof membrane (like bitumen or single-ply membranes), while in pitched roofs it is used as slabs or rolls between or over rafters. Although the insulation core itself is unfaced, it can optionally be supplied with facings such as aluminum foil (for vapor control) or glass cloth (for added durability in industrial or HVAC applications), but these are not used as outer weatherproof layers. The final outer covering in roofing is always a separate waterproofing material.