I'm not sure what conclusions, if any, can be drawn from these observations but I ran across them in my backpack writings from several years ago and thought they might be of interest to others.
While in the tent, in my clothing, in my sleeping bag, in the daytime, in the rain, in the summer, in the mountains, in Washington State I measured the temps as follows:
Inside tent 65F
Inside sleeping bag 80F
Inside clothing 95F
Inside skin (assumed) 98.6F
Looks like tent, sleeping bag and clothing each added 15 -20 degrees F to the equation as I went from the outside temp of 45F to the inside-me temp of 98.6.
The most crucial piece of the equation would be the tent. Without it everything else would get wet and lose heat. I could survive (uncomfortably), on the other hand, with the loss of either sleeping bag or clothing as long as I was in the tent.
Correction.....skin would be the most crucial piece. Without it nothing else would matter.