It is often believed that keeping your head warm in the cold may literally mean the difference between life and death. I certainly subscribe to this philosophy. While it makes sense to keep as warm as possible and to cover exposed skin in cold weather, I do wonder how important it truly is to keep you head warm?
First, as you likely know, body heat is lost through the skin. Your body uses sweat to cool you down and hair and clothing to keep you warm. Often the one exposed part of the body is your head and face. It would naturally follow that you’re going to lose more heat through your head more so than other parts of the body simply because your head is exposed to the elements and the rest of your body is not.
Second, you should understand that the body loses heat much faster when exposed to windy conditions (at several times the normal rate) and astonishingly fast when wet (at dozens of times the normal rate). Thus, when cold and in either windy or wet conditions, your body—specifically your head because it is exposed—will lose heat VERY fast. That’s why it is critical to avoid getting wet or being in the wind when it’s cold out.
Now, if you do a bit of surfing on the Net or read a few books on the subject, you’ll see varying statements that say you can lose between 7 and 80 percent or more of your body heat through the head. Not only is that a huge discrepancy in range, let’s also be realistic for a moment. Considering that body heat is lost through the skin and that the skin on your head represents less than 10 percent of your total skin area, I would find it hard to believe that 80% of body heat could be lost through the head. That makes little sense.
On the other hand, it is far more probable that you could lose around 7% of your body heat through your head since that is roughly the amount of exposed skin on the head.
Most claims I can find indicate that the number should be more like 20 to 30 percent of body heat is lost through the head. While significantly less than 80 percent, these numbers would still represent a large amount of heat lost relative to exposed skin.
Could this 20 to 30 percent claim be more accurate?
As I mentioned earlier, when the body is subjected to windy or wet conditions, the body will lose heat much faster than it otherwise would. This could act to support the 20 to 30 percent claims assuming your head and face are the only exposed parts of your body.
Also, it is likely that you’ll be working more strenuously in cold weather conditions simply to survive and, as such, you will lose more body heat through the head in these conditions because more blood will be flowing to the head. The reason for this is because the forehead is filled with many blood vessels that help to regulate our body temperature. When this area is exposes to cold, windy, or wet conditions (especially under strenuous conditions) it follows that more heat would then be lost. Precisely how much would depend on the individual, weather conditions, and so on. Again, this could also support the 20 to 30 percent range claims.
I think it would be safe to say that the head loses little more heat than the rest of the body under normal conditions, but could lose significantly more heat under extreme conditions.
Therefore, it would make sense to keep your head warm—especially your forehead—in order to retain as much heat as possible in cold weather conditions. It would also make sense that whatever you use to keep your head warm should be breathable as you wouldn’t want to work up a sweat only to have a wet and cold condition after you later cool down.
So, the obvious advice would be to limit your exposed skin as much as possible including your head and face with something relatively breathable and to do so BEFORE you’re already freezing and sweaty!