I found this when i Googled it.
Let me start by saying that every square
inch of skin on the human body is
capable of allowing heat to escape. That
is to say, if you wear a jacket with no
pants, your legs will lose more heat than
your torso -- but if you wear pants with
no jacket, your torso will lose more heat
than your legs. Both areas are capable of
losing heat -- and will do so more quickly
when exposed. Therefore, any part of
your body that's more exposed to the
cold than another part has the potential
to lose more heat than other than parts
that are less exposed.
This is fairly obvious, but I mention it
for completeness' sake. This generally
means that you should try to cover
yourself as much as possible, especially
larger skin surfaces like the torso.
However, the point that I think the OP is
trying to get at is that -- all else being
equal -- every square inch of exposed
human skin does NOT lose heat at
the same rate . That is to say, some
areas of skin lose heat faster than
others. If you were to stand in the cold
totally naked, some parts of you would
lose heat more quickly than others. This
is an indisputable, biological fact. Allow
me to explain:
Human blood serves many functions --
one of which is thermoregulation. As an
evolutionary adaption, humans have
areas on their body that are especially
suited for releasing heat, in order to cool
us off when we get too hot. In these
areas, there is a high volume of blood
flow, and that blood passes very close to
the skin. These areas are:
The skull
The groin
The armpits
Some might also say the
extremities, like fingers and toes.
In these areas, there is a lot of blood
flowing around, and the skin is fairly
thin, allowing heat to escape from the
blood more quickly than in other areas.
Therefore, if you are in a desperate
survival situation where you risk
hypothermia, these are the areas of the
body you should focus on keeping the
warmest.
Armpits are fairly easy to keep warm,
just keep your elbows down and they'll
be insulated by your torso and upper
arm.
It's important to keep warm, dry
underwear in order to keep your groin
warm as well.
And yes, YOU SHOULD WEAR A HAT.
While you might not lose the "majority"
of body heat through your head, it is
one of the areas of skin that loses heat
most quickly and it should be one of the
main things you focus on keeping warm.
The extremities are also important to
keep warm. I have friends that go out
jogging in the winter wearing shorts and
a t-shirt. They don a warm beanie and
gloves right before they go out, and
those are all it takes to keep them warm
in freezing temperatures.
In summary: If you have clothes or
ways to protect every inch of skin on
your body, you should do that. I thought
this was basic common sense, but people
were squabbling so I'll reiterate.
However, if you only have limited means
of protection and you need to focus on
warming only a small area of your body,
you're best off focusing on the four
areas listed above.
