For arguments sake, lets say the air temperature is 50degrees F with zero air movement (no wind chill factor). A naked person stands still in that environment. Arbitrarily let’s say the person looses 1000 BTUs in an hour. By the “debunk” SBA rule, the head (9%) would account for 90 BTUs while the remaining body would give off 910 BTUs.

Now, if we clothe the body (not he head) with clothing that achieves 70% efficiency. That would mean that 30% or 273 BTUs are still lost from the areas of the body other then the head. 273 + 90 BTUs = 363 BTUs so the loss from the head is now 24.79 % of the total heal loss.

If the body were clothed in clothing that provides 80% efficiency, then 20% would represent 180 BTUs of loss from non-head regions of the body. 180 + 90 BTUs = 270 BTUs. So now the heat loss from the head is 33.33…%.

So you can see, the greater efficiency of heat retention of the clothing worn on the body, there is a greater percent of heat loss from the uncovered head.

Comparing core temperature to BSA heat loss is like comparing apples to oranges. The body will divert blood flow to various parts of the body to maintain a survivable core temperature for as long as possible. If the “study” was not conducted with thermal imaging, then it is flawed.

Pete