A composite insulating material which is comprised of one or more layers of open ended cells formed from flexible thin plastic sheet, and may be fastened to one or more cover sheets. The material is flexible enough to be worn as clothing and derives its insulating properties by reducing thermal conducting paths and areas, by introducing numerous controlled geometry air cells between the heat source and inner layer to further lower conductivity and inhibit convection currents and, by absorbing radiant thermal energy within the cell walls thereby reducing heat transmission by radiation. Metallized reflecting layers are not required to achieve high insulating efficiency.