Do you lose most heat through your head?
If so then a hat is essential in the chilly winter months to stop you from succumbing to the cold. Some versions even put a number on the proportion of heat lost through the head. Depending on how charitable you are feeling, the rumours are either misleading or downright wrong.
This myth probably stems from misinterpretation of the results of early studies of human heat loss. If you dress someone in good warm clothes, don’t give them a hat and then throw them into the cold — as happened in those studies — most of the escaping heat will go through their head. That is, after all, the only place it can easily escape. Throw the same person out in the cold naked (or, if that makes you blush, in a swimsuit) and now they will lose heat all over their bodies. Since they are losing more heat overall the proportion lost through their head drops. There’s nothing special about the head.
That’s the science, but this myth can easily be debunked from the armchair. If it were true then you would feel colder if you went without a hat than if you went without pants. And divers could do without a wetsuit altogether as long as they wore a hood.
There are some subtleties. The head may be a little more effective at dissipating heat when you are overheating. But by and large the head dissipates heat at the same rate as other comparably sized parts of the body.
This doesn’t mean a hat is useless — just not as essential as you may have thought. You can still lose plenty of heat through your head and you will cool down faster without a hat than with one. If you’re planning to frolic in the snow all day it makes sense to include a hat in your ensemble. But if it’s just a nippy day and you’re worried about hat hair, you’re unlikely to keel over on the way to the corner shop. The cold hard fact is that you don’t lose most of your heat through your head.