The mineral wool insulating panel is encased to prevent the emergence of fine dust. The casing has a higher vapour diffusion resistance on one side which is reached by using a metal foil lining whose shiny side faces the insulating material. The casing can be thin clingy plastics. The volume of the material is reduced by air extraction. The material has the shape of known insulating wedges set in an air-tight casing from which the air is extracted.
