Insulation material

The insulation material has an upper side (2), a lower side (3), a thickness (4), a zone of high density (5) and a zone of low density (6). The zone of high density of the insulation material has an indentation hardness which amounts twice the indentation hardness of the zone of low density. The zone of low density occupies 60 percent of the thickness of the insulation material. The surface weight of the zone of high density engages up to 50 percent of the total surface weight.