Clo values for clothing. Additive or not quite?

[Moondog55]

Not such a simple question and I admit to my arithmetic being in need of some refreshing.

I have been fighting my way though a BPL thread where the distinction is made between Clo value of the basic fabric in the intrinsic Clo [iClo] value of a garment
This makes sense as some garments obviously cover more or less of our body
I was trying to work out how effectively warm I would be using the LW layering combination I have would be and whether i could safely leave the belay parka behind if I get to go away this winter

http://www.backpackinglight.com/cgi-bin ... d_id=18950

Extrapolating from Richards tables and guessing the iClo value of the Cap2 T-shirt to have an iClo value about halfway between the silk weight and a cotton T
Cap2 T-shirt ~0.25
Powerstretch top ~0.5 [ only 11% elastane and no nylon]
ALDI fleece hoody ~0.5 [ it's Polartec 100 equal and it has a good hood]
MB LW Thermawrap parka ~0.75
This totals ~2Clo which is what I would think was minimum for an Australian snow trip
I have the windshirt tho and that will make a difference but not so much as the Thermawrap is itself windproof
These 4 layers weigh in at 1585 grams and while not tight are slim and form fitting.
There is not enough room to wear a vest under the insulated MB parka but that combination would fit inside the belay parka easily
I worry too much I know
So what's the iClo value of the inner windproof layer and of the outer shell garment and how much can I assume for the extra beanie ?
Legs are another matter

[stansi]

Talk about overthink a problem.
for *&^%$# sake your in Australia.

[Moondog55]

Yes I admit to thinking very deeply about the problems
But not just Australia stansi; apart from planning to spend next winter camping at Falls Creek the Boss and I will then be headed for a North American winter and I'll be hoping to get some high peaks summited

[slparker]

Surely there are more variables to being warm than the warmth of your garment? Such as individual cold tolerance (i.e. acclimatisation), individual subcutaneous fatty tissue, BMR, hydration, nutrition, outside humidity, wind, altitude etc.
My point being that other variables would outweigh any precision that you might get out of clothing choices.

[Moondog55]

True; but getting the right warmth with minimum weight is the reason for the thinking and while down gives the greatest warmth for weight it does have little warmth when wet and dries very slowly in an Australian winter.
Partly also I am intrigued by the fact that the cheap ALDI thermal layers so well over what I already have in my quiver and that these layers fit under any of my insulated parkas and the 100 weight is a quarter of the weight of my fleece parka and so much less bulky

[Moondog55]

Surely there are more variables to being warm than the warmth of your garment? Such as individual cold tolerance (i.e. acclimatisation), individual subcutaneous fatty tissue, BMR, hydration, nutrition, outside humidity, wind, altitude etc.
My point being that other variables would outweigh any precision that you might get out of clothing choices.

I need to work out what is the MINIMUM I theoretically need for an MET of slightly less than 1 for those occasions when I am cold wet and tired
Not taking either my belay parka or my big down parka saves a kilo and a half and 12 litres of space in the pack and there are many times when you do not want to crawl into the tent and sleeping bag and the extra lightweight layer can fine tune a system for when the underwear and windshirt are not warm enough and the parka is far too much
The combination of the LW fleece and the Thermawrap is less than the single 300 Polartec they replace and less bulky too and because of the windproof shell on the Thermawrap possible warmer. And that is what I am trying to determine
I'm interested in other peoples take on the one very warm layer or two lighter layers as I am slowly changing my gear for slightly less heavy stuff as I find the money