Separation layer Protective and separating layers are made using fiberglass or geotextile. As a separation layer between the PVC membrane and thermal insulation based on extrusion foam polystyrene, it is recommended to use TechnoNICOL fiberglass weighing ≥100 g/m². TechnoNICOL separation layer: fiberglass mat of 100 g/m2 Fiberglass a material made of randomly positioned monofibers, bonded together using a synthetic binder.