Comfort
Skiing takes place during the winter. Typically this
means it is cold outside. It can also be a very physically
intense material so it can result in sweating.
Boots have to create a specific environment to protect the
users foot and ensure comfort, so climate control is an
important issue. Insulation is used to keep the foot warm by
creating a barrier that prevents heat exchange. However, if a
material gets wet this can spell bad news for a skier. Water
transmits heat at 4 times the rate of air (which is oftentimes
the barrier used, done by using light materials to create
space).
The foot doesn't have any major muscles and is warmed primarily
by blood flow. Bad fitting ski boots (as in possibly cutting off
circulation) combined with cold temperatures perform a one-two
punch that could quickly lead to danger.