It’s an often-repeated, slightly wonky story. Cover your head on a cold day, because 40 percent of your body heat exits through your cranium. Or 60 percent. Or 80 percent. Sure, the explanations are a bit dubious—the skin on your scalp is extremely thin, heat rises, and if you’re wearing clothes the heat has nowhere else to go—but who can question such an enduring yarn?
Serious-minded scientists have pointed out that if the 60 percent figure were true, you’d be more comfortable on an Alaskan cruise with nothing on but a ski hat than if you were fully dressed but bare-headed. So perhaps it’s no surprise to find that the true figure is somewhat less than 10 percent. In fact, you lose little more heat out of your head than you lose from any similarly sized part of your body, although your face, head, and chest are more sensitive to temperature changes, which may give you the impression that you’re colder.
This confusion might have resulted from a flawed interpretation of a military study that examined heat loss in fully dressed soldiers. The soldiers were bundled up in survival suits, but hatless, so their heads did account for about half of the heat they lost. (If they war-gamed naked, the equation would change.) In any case, a hat remains a sensible addition to any cold-weather ensemble.
Source of Information : Oreilly - Your Body Missing Manual