The HeatSheet blankets and bivys are excellent tools, you just have to understand that they need to be integrated into a system. That system may use natural materials for insulation from the ground. You also have to appreciate that they are ultralight, ultracompact components and it's incorrect to compare them against a wool blanket and down sleeping bag.

These AMK products are far, far better than the old Mylar sheets. Even professional survival curmudgeon Peter Kummerfeldt has become a convert. For years he railed against Mylar blankets, and quite rightly so. But recently he was introduced to the much better AMK versions and he likes them.

The AMK products give you a very light, very compact, and very FAST way to keep wind & water at bay. Combine them with some simple bushcraft and hopefully a fire, and you have a truly useful asset.