It is very common for parents to advise their children to wear a hat or to cover their head when its cold outside, with the reasoning behind this advice often cited as “most of your body heat escapes through your head” or “you lose heat faster through your head.” People often rationalize why this might be the case stating such things as: “It’s because of the large amount of blood combined with the lack of much insulation like fat and the like on your head.” It turns out though, this just isn’t correct.
This misconception seems to have been popularized by a U.S. army survival manual in the 1960s. The U.S. army conducted studies to test the loss of body heat in extremely cold temperatures. The results of these tests ended up giving rise to a section of the manual stating a person “can lose 40 to 45 percent of body heat from an unprotected head”. The problem is that this doesn’t tell the whole story. What needed to be added is that the subjects of the tests wore survival suits designed especially for the cold, but didn’t wear anything on their heads. So it shouldn’t come as a surprise that the subjects lost a large percentage of their body heat through their heads.