It is a stone wool board faced with aluminium foil on one side used for external thermal insulation, internal sound insulation of air conditioning and ventilation ducts.
Before the boards are applied, duct surfaces to be used are cleaned to make sure the surface is free from dust and grease. If cold air insulation is going to be applied for the external thermal insulation, definitely the boards faced with aluminium foil should be used against condensation risk. The boards are installed into the pins (5- 6 pins per m2) fastened to the outside of the duct with foiled side facing the exterior. Board joints are sealed with self adhesive aluminium foil tape with great care to ensure that joints are water impermeable.