I've been discussing with some friends the idea of your head being a major source of heat loss or not. Somehow I've gained the impression that your first goal for warming up should be to add insulation to your torso (regardless of your current state of dress - i.e. even if you were completely naked or already completely clothed). Others argue that putting on a hat would be the single more effective addition (in this case, assuming you were already wearing clothes).
I'm pretty sure the source of my idea came from some of Mr. Nisley's posts, where he tended to treat the hooded and non-hooded versions of clothing items as the same, except that since the hooded version covered 7% more body area, it was therefore 7% more effective. Was that just a simplification for us, or is it really that simple??? i.e. is the key to heat loss just covering as much body area as possible, or are certain areas significantly more important?