Of course, not many of us lay out under the stars buck nekkid and those that do are probably beyond help. <img src="/forums/images/graemlins/grin.gif" alt="" />

The things we do to insulate ourselves also shield us from losing heat through radiation. The simple calculation being referenced is the potential heat loss in an "ideal" situation. Real world heat loss is going to depend on many factors- clothing, a tent, and a sleeping bag completely changes the equation. If it didn't, we'd be in trouble.