Multilayered sheet insulating material for heat insulation and sound proofing having at least two separation layers made of flexible material, such as sheets, non-woven fabric, paper or the like, and spacer elements between the separation layers. The spacer elements are formed by spacer fibers which are oriented perpendicular to the separation layers, and at least one end of the spacer fibers is linked, e.g., by adhesive, to a separation layer. The sheet insulating material also includes supporting fibers arranged between the separation layers and proximate the spacer fibers for supporting the spacer fibers. The sheet insulating material has very good insulating properties, a particularly low weight and high flexibility.