At what temp do you leave your Thermawrap (or similar) at home?

I should admit that I haven't camped in the middle of winter and never at temps like that. But I have snowshoed in the mountains a lot. Twice last winter I went out when the temp at the trailhead might have been -10 F, and there was a cool breeze blowing up the mountain. And I got cold, very cold, coming down and a bit scared (the first time I have ever been afraid of the cold).

What I came to realize was that my layering system, much like yours, was fine for temps from -5 to 30 or so, particularly moving, but that it started breaking down at -15 with a wind chill. I couldn't get my hands warm, my feet in my insulated boots were getting cold, etc. I thought if I moved fast I would warm up, which was wrong, and so I made the mistake of not stopping and putting on everything I was carrying. But that was just a dayhike. I couldn't imagine stopping to camp in those temps with the wind and snow swirling around. Hiking at -20 is just as far from +10 F as 60 is from 90, and so I don't think we can think of them as similar.

So the point of all that was if you are really going to facing sub 0 temps, you are going to want all the warmth you can carry, and that means the Nuptse. The thermawrap alone, even with everything else on, is not going to be adequate once you stop even for a short time.

The Thermawrap/Micropuff would be not even close to enough insulation. I wore a Micropuff over a baselayer top and fleece pants over a baselayer bottom around camp last December. It was about 15-degrees and I was only sitting around camp for an hour before heading into my sleeping bag but that was one of the coldest hours of my life. Definitely not recommended. I would say that a Micropuff would only be warm down to maybe 35-degrees. Check out some of Richard's excellent posts about the clo values of various insulation pieces for scientific backup to my experience.

Richard's posts:

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/15085/index.html?skip_to_post=112653#112653

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/13697/index.html?skip_to_post=101439#101439

That's what I thought. Thanks for the input, and I plan on putting the jacket to the test this winter. At some point, I'm going to determine my failing point for the jacket.

I would replace the Power Shield jacket with something like a Patagonia R2 fleece, warmer for almost the same weight. Use the Rab shell when the wind blows.

I don't have an Event jacket to compare breathability but it is in those kind of conditions that a Houdini or Ready Mix shell would excel.

Insulated pants and sitting on a pad in tent or out helps staying warm, especially your extremities. I have used my Nunatak Skaha Plus with 2 oz overfill down to -5 with comfort, if that compares to the Montbell.

My upper body for cold is:
Patagonia Capilene 1
R1 Hoody or R2 jacket
Ready Mix or Houdini
Nunatak Skaha Plus or DAS Parka

I'm taking Thermawrap pants and two closed-cell foam pads, all of which will be accessible during stops.

What weight of Polartec fleece would say the R2 compares to? Like most folks, I've got a variety of fleeces to choose from.

I would say the R2 is closest to the Polartec 200 fleece.

I think its the same as the Mountain Hardwear Monkey Man fleece.

I've camped outside during temps of -10 to -20 quite a bit, and in my experience no clothing item short of a down suit will keep you warm. You'll either need a fire, or be in your sleeping bag.