What's your preferred fabric/fiber for long underwear?

It’s winter, and it’s cold! in Northern Europe, and long underwear is very appropriate for the season. To avoid hijacking the “It ain’t the cold, it’s the humidity” thread, I’m taking this question to a new thread
Here’s my opinion on long underwear fibers:

[li]Wool: The warmest, the bestest in really cold weather. Plenty of insulation even when damp or wet. May get clammy if you’re sweating a lot (like when doing sports). May itch if you’ve got sensible skin and have chosen the wrong brand.[/li][li]Polypropylene (PP): Excellent wicking properties. Poor insulation when wet. When used for some times, it starts to stink, and a set which has been used for sports for the time of one (1) season will stink like roadkill after wearing it for half an hour even if it’s straight from the dryer and even if it’s been washed after every use.[/li][li]Polyester: Good wicking properties, bur poorer than PP. Better against the skin than PP. Not as offensive in the olfactory department[/li][li]Cotton: The worst. choice. ever. if wet. Comfortable against the skin for low activity. Less warmth that the other alternatives.[/li][/ul]

What’s your opinion?

If I lived in a climate that actually had winters*, I’d probably go with silk, with cotton as a runner-up. I haven’t found ANY kind of wool that won’t make me itch. I’ve never found any polyester to be any warmer than cotton.

*I live in North Texas, and while we occasionally get snow here, we really don’t have much in the way of winter.

The temperature in Stockholm today is circa -15 celcius and I am very comfy in my silk long johns. I have used polypropylene as well but for me silk wins the day as you can keep them on indoors without becoming insanely sweaty.

Who can wear wool?

Polyester likely.
Polypropylene if I had it.

I have a set of polypropylene underwear I use at work when it drops below -10 C or so and they are absolutely great for that, but I wouldn’t really want to wear them indoors for any prolonged periods of time. And yes, they smell a bit, but it’s not really an issue at work - after I get home, I peel 'em off and take a shower as the first thing every time. Them and my goretex work clothes together with proper hat + balaclava, double gloves and so on keeps me easily warm all the way to -30 C which is as cold as it gets here. I can’t even wear the goretex coat’s inner layer at that temperature yet without getting hot.

My “civilian” long underpants are polyester, and while they aren’t as great in extreme temperatures, they are very comfy.

It’s all about the silk. It’s lightweight for it’s insulating power and I have it in various weights ranging from light for under work clothes to a much thicker version for tramping through the outdoors.

I don’t need long underwear for athletic endeavors, but I can tell you that for office wear silk can’t be beat. Much lighter, so it isn’t too bulky for your regular clothes, and nothing catches or binds on it.

Silk, please. When I lived in Chicago and walked/used public transit (and therefore was outside all the damn time) I had a pair of silk long underwear and they were great. Non-bulky, but very insulating and warm. I will never go back to those huge waffle-weave things again.

There are lots of proprietary fibers, other than polypropelene, many of which address the stink problem. I like CoolMax/Thermax and and the REI brand, but my Duofold Thermastat long undies are the absolute best.

Silk is fine for everyday and for walking but it doesn’t have enough give for sports where you might take an uncontrolled tumble, like skiing. It can feel “hard” and even “sharp” when the fabic gets tensed.

Other. Not sure exactly what it is, but I have “caprilene” IIRC. It is fantastic.

Silk is my fave, although synthetics are fine too (much cheaper). Wool/wool blend makes me itch terribly if it’s against my skin. I have a wool pair but I wear them over a silk pair if I need to stay extra warm.

raises hand

FTR, the itchy wool longjohns I had to use when I was a kid are totally different from the modern, soft, superwash-treated wool underwear we can find in the stores today. Those two things are worlds apart.

I think that if I could afford a good-quality set of silk long underwear, I’d go for that. But since all I have is a pair of too-large bottoms that I wear to sleep in, my vote goes for polyester (which I have several pairs of, and also sometimes sleep in). It’s soft, it’s cheap, it’s machine washable, and most important for me, it doesn’t hold BO like polypro.

I’d like to try silk, but mine are polyester. They’re okay.

“Smartwool” brand 100% Merino Wool long underwear. They have a lightweight and a microweight style that are great if it is cold but you are hiking or staying active. The wool is not itchy at all, it feels like a soft cotton tee shirt to the touch.

Smartwool has a zip up turtleneck that I love for heat regulation and keeping drops of water, pine needles, and crap from going down the back of your neck.

Merino wool is luxurious. Spendy, but totally worth it.