Bill's 0F Backpack Requirement Analysis
Walk around camp----------2.341
UL Back Pack Min----------1.756
UL Back Pack Max----------1.003
Assuming no wind penetration and no body movements to pump air around, conventional clothing insulation (cotton, silk, wool, rayon, etc) = 0.15 x weight of clothes in lbs. (i.e., 0.15 clo per lb of clothes). So 10 lbs. clothes = 1.5 clo.
Using the average for synthetic high-loft insulations, they provide about 4.7 clo /inch in a lab and about 4 clo / inch when worn. So using the conservative 4 clo number it would take 1.756 / 4 = .439" while UL backing at 0F.
My off-the-shelf high tech approach would be to wear, a thin long underwear base layer for moisture management and my Patagonia Puffball jacket and pants for insulation while UL backpacking at 0F. At .6" loft they are about 27% loft overkill for this application. They would have to be partially unzipped to vent the excess heat while UL backpacking. My L hooded jacket weighs 17oz and my L pants weigh 16oz for a total of 33 oz. .6" loft * 4 clo effective = 2.4 clo. 2.4 clo / 2.06 lb = 1.17 clo per lb of clothes. In other words, a representative off-the-shelf high tech solution, to this problem, is about 7.8 times more weight efficient than conventional clothing.
For sitting around camp I would add a 800 fill 3/4" loft down vest under my Puffball jacket. This would provide 1.77 clo of incremental whole body insulation if it wasn't layered under my jacket. Do to the compression of the jacket the insulation would change from abut 1.77 to 1.51 for a total of 3.9 clo. I would have to only very slightly vent my ensemble from overheating because it is greater than the 3.5 clo I would require for sitting around.
For sleeping, I would augment my day time insulation with my quilt or bag and pad insulation. I would try and layer my synthetic insulation at the top of my sleeping ensemble so that the dew point would fall there or above. This is where the optimal solution becomes more complicated and I discussed only one option of many in the forum topic dealing with torso blankets.
Note that I used a value of 4 MET for min hiking and 7 MET for max hiking heat generation. 7 MET is about the maximum that the average person can sustain for a full day. You could have short MET burst rates more than double that amount. You just unzip your jacket, if necessary, after a short MET burst.