"I would think that since a considerable percentage of body heat escapes through the head"
Don't agree. I will use Wills own words:
"First, let’s deal with the myth: “If your feet are cold, cover your head because you can lose up to 75% of your body heat through your head alone.” Yes, it’s a myth, and we believed it ourselves for many years. The head is only about 10% of the body’s surface area, and it would have to lose about 40 times more heat per unit area compared to the rest of the body for this statement to be true.
The folks at the Wilderness Medicine Institute ran an experiment on student volunteers and found the rate of heat loss is relatively the same for any exposed part of the body. A person does not lose heat significantly faster through the scalp than any other portion of the body with the same surface area. The idea that we lose heat 4000% faster through our head, because of the constant blood supply to the brain, is simply a myth."
Still I like the hood on the Flash and also combined with a BPL Beartooth top I don't need a warm hat outside of winter. The flash keeps my head warm in camp and the Beartooth on the trail with its hood.