They say you loose 80% of your heat out your head. But how much of that is your kneck?

Top of your head's got hair on it to keep you warm. your neck? Completely exposed to the elements. 

And where does your neck stop and head start.

For some of us it's less clear, especially in the front. In the back nobody knows. 

Ok I'm going to do some audience participation. 

Tell me when I get to the top of my neck. Say when.

(Use microphone as indicator and slowly slide up the back of the head over the top and down.)