Snippet from the article:
When it comes to wrapping up on a cold winter’s day, a cosy hat is obligatory. After all, most of our body heat is lost through our heads – or so we are led to believe.
Closer inspection of heat loss in the hatless, however, reveals the claim to be nonsense, say scientists who have dispelled this and five other modern myths.
They traced the origins of the hat-wearing advice back to a US army survival manual from 1970 which strongly recommended covering the head when it is cold, since “40 to 45 percent of body heat” is lost from the head.
Full article here — Scientists debunk the myth that you lose most heat through your head