That parka in the picture above looks cozy, along with the pants/mitts/hood.
Looks like fairly even coverage once all zipped up for an extreme condition.
Here is a formula for clothing inches, converted to english units
assuming even coverage and dry feet...
inches of clothing, I = (90-Ta)/50n - Ia
90 = Ts = skin temperature in comfortable state
Ta = air temperature in degF
n = metabolic rate
Ia = air inches (reduced by wind chill)
n = 0.72 sleeping post digestion
n = 0.80 sleeping while digesting
n = 0.80 lying post digestion
n = 0.90 lying while digesting
n = 1.0 sitting = ~100 kcal/hr for 2m^2 surface area
n = 1.2 standing
n = 1.8 slow level walking 2.5 km/hr (light work)
n = 2.6 level walking 5.0 km/hr
n = 3.6 brisk level walking 6.5 km/hr
n = 4.4 walking up 5% grade at 5.5 km/hr
n = 6.8 walking up 10% grade at 5.5 km/hr
Ia = 0.2 inches in still air, 0.1 inches in 2.5 mph wind, 0.05 in 12 mph wind, 0.02 in 50 mph wind
Examples,
-30F, standing in camp, 2.5 mph wind...
I = [90-(-30)]/[50x1.2] - 0.1 inches = 1.9 inches of clothing needed
-40F, level walking at 5.0 km/hr into 15 km/hr wind...
I = [90-(-40)]/[50x2.6] - 0.05 inches = 0.95 inches of clothing needed
0F, light camp work, still air
I = [90-(0)]/[50x1.8] - 0.2 inches = 0.8 inches of clothing needed
18F, brisk level walking 6.5 km/hr
I = [90-(18)]/[50x3.6] - ~0.07 inches = 0.33 inches of clothing needed
references/assumptions:
http://dspace.ncaor.org:8080/dspace/bitstream/123456789/291/3/article31.pdf75% of heat loss is conductive (i.e. non-sweating 33degC skin temperature)
4 clo per inch = 6.2 tog per inch (i.e. good insulation and thin shells)
1 MET = 100kcal/hr sitting for 2 m^2 of surface area
full and consistent thickness coverage, dry feet
neutral thermal radiation
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