Abstract: An insulating sheet material is made of a plurality of air tight chambers, each having a partial vacuum therein, held together in closely spaced side-by-side relationship so as to form a sheet of such compartments. The insulating sheet may be formed of sheets of material bonded together so as to form the side-by-side compartments, or the compartments may be individually formed and secured in side-by-side relationship by a film of material to which the compartments are adhered. The insulation sheet is preferrably perforated between compartments so that the sheet can be easily torn to any desired size.