Moms everywhere have been known to tell their children to keep their heads covered in the cold because that is where most of the heat loss occurs in the body. This advice stems from the long-held belief that 40% to 80% of our heat is lost through our heads. This is a myth, however.
The myth may have come about from military experiments in the 1950s, where subjects were exposed to low temperatures with their heads exposed while their bodies were covered. Researchers found that 40 to 45% of heat loss was from the head being exposed, but they didn’t account for the subjects’ bodies being covered.
A 2008 study in the British Medical Journal may have finally put the question to rest with a more controlled study. They found that about 7% to 10% of heat loss was attributed to the head. They discovered this percentage by testing subjects with and without wetsuits in cold water and with and without their heads submerged.
The researchers concluded that heat loss is largely dependent on the surface area of the body that is exposed, and the head only represents about 7% of the surface area of the body. Heat loss is almost proportional to the amount of skin showing. You would then lose more heat without pants or a shirt than you ever would by leaving your head exposed.
Of course, it’s still a good idea to put on a hat when there are frigid temperatures outside. Why should you be colder than you have to?