60g Nano Puff pullover as the outer layer, mid winter, 12K feet
That is a common hit list for the aspiring alpinist wanting to get in some altitude.
So it is just as common to answer questions about the gear required to make that dream come true.
I had to walk down to my gear room and count the synthetic and down jackets I own specifically to climb in. The count is split 50/50 between Primaloft One and Down in the 850 fill range.
The reason I mention the 50/50 split and not the numbers (besides embarrassing myself as a clothes hog) is to hopefully show I am not biased one way or the other for insulation. The only thing I care about is "will it work for my own use".
In the last few years the one item of clothing that has impressed me way beyond any other is a 60g weight Primaloft or Coreloft layer. Most easily identified as the Arcteryx Atom Lt or the Patagonia Nano Puff series are 60g. But almost everyone makes one these days.
I first saw full zip and hooded prototype samples from Mtn Hardware (which eventually became the Compressor with 100g layer Primaloft and then changed again). The RAB Xenon is very close at 60g to the original prototype and one of my current lwt. favorites. And then Patagonia Nano Puff pullovers started showing up in places I never thought reasonable. Pictures of one or the other from the top of the Grand Jorasses in winter and summit of Denali early Spring for example. Not as inner layering pieces mind you but as the outer insulated shells. All 60g of that Primaloft One being used to the fullest.
I have Down sweaters that are every bit as capable...as long as you can keep them dry. As mid weight insulation and your outer climbing layer Down doesn't stand a chance if you are working hard unless the sun is out and it is cold and dry. When the moon and stars align Down will work fine. The rest of the time given the chance, Primaloft is what I'll bet on. And more importantly if I'll be working hard and know I'll eventually need the insulation I am wearing, Primaloft is a better bet to still be working at full value when it is required.
But lets face it is you can get by with only 60gs of Primaloft it isn't very cold outside. Even mid winter at 12K feet. OR you must be working pretty hard! Some time back I was laughed at for saying I sweated and got my insulation wet on lead. Work hard enough on technical ground or go fast enough on easy ground and you'll sweat. How you are able to manage that moisture in your insulation is key.
Soak it out and replace it is an option for approaches. But that won't work on the actual climb generally past your gloves. So having clothing that will dry out in use and most importantly keep you dry while moving is always going to be important if you are working hard enough.
Back to the layers? As I continued to pay attention to other climbers kit I started noticing a few guys using two 60g layers. That is 120g plus the 4 layers of nylon in some even colder places. 100g jackets are common enough as light weight belay jackets. How about layering a 60g jacket and a 100g jacket? The Arcteryx Atom SV and Patagonia Micro Puff are 100g jackets. The Patagonia DAS 170g.
With two lessor layers of insulation but more versatile garments you are now bettering a DAS' insulation with the two additional layers of nylon shell.
I find it humorous that people still want to argue which insulation (down or synthetic) is the better one for the outdoors. For many that might be Down. But anyone who really has to rely on the insulation they climb in will generally bring a synthetic jacket and a down bag. I saw plenty of Down jackets on skiers last winter. None on the climbers in the huts or on the lifts fwiw.
Here is a more varied discussion on the same basic topic:
Last winter I had down and synthetic jackets with me. When I skied I too used Down. It was also clear and sunny every time we skied. When I climbed I used synthetics. Much of the time it was with several layers intentionally.
There are some good down jackets available. Some of the better ones I have seen were reviewed here. on the blog.
I have a good many choices in the closet and find myself actually using 2 layers of 60g. a lot. Or a 60g layer and a 100g layer. When it is really cold I'll add two 60g layers and the 100g piece as the third layer.
Remember the idea is to stay dry, to stay warm. Layers allow you to regulate your heat output and just as important how much heat you conserve. And how mobile you are as well. Options in the mountain are always a good thing if you don't have to pay a premium for them. If you gain something..like mobility it is a win!
Layering synthetics (or even a combination of down/down or down/synthetics for that matter) is just another option to think about. And one way to avoid ever buying that heavy weight belay jacket that you likely will never use and just as likely never want to carry.
Layered up for the -30 temps and a bivy
4 layers of Synthetic, top down, 60/100/60 and 60.
Two previous posts that you might find interesting on down/synthetics