Metal heat insulator

In a generally elongated, thin, metal sheet heat insulator having at least two generally elongated, thin, metal sheets disposed generally one above the other in a spaced apart relationship and a metal separator therebetween contacting both said sheets for maintaining the spaced apart relationship, the improvement comprising:

• non-woven, substantially open, metal separator which is not permanently attached to or part of the sheets and as a substantial Z-direction dimension and has substantially parallel upper and lower contact surfaces spaced apart in a Z-direction;
• said separator being in the form of a twisted expanded metal foil having spaced apart substantially vertically disposed portions and cut twisted portions connecting the vertically disposed portions and the vertically disposed portions extending further from a central plane of the foil than the twisted portions such that the twisted portions do not substantially contact the thin metal sheets and the upper contact surface and a lower contact surface formed by the vertically disposed portions have contact surface areas of less than 5% of a planar area of the separator parallel to X and Y-dimensions of the separator.