What's a really good pair of thermals?
You're questions a bit ambiguous, and I’m sorry that I don’t know more about you to give accurate advice, so I’ll have to stick with my own experience.
I only wear wool. This comes after years (I’m 46 and one half) of going back and forth between wool and synthetics. I cannot wear the synthetics because I perspire a lot whenever I exert myself. Hence, I quickly overwhelm the manmade fibers. I don’t
mind synthetics and fleece while I’m just sitting still,
but when I sweat, they get quite itchy on me. They feel warm as soon as I put them on, but if I do anything at all, I’m quickly overheated, I get soppy wet, and the cold sets in.
Odd how synthetics itch me, but I’m ok with most wool.
Since going back to wool about six or seven years ago, I was
quickly reminded why I used to wear it. It deals with my perspiration well. Please note, I’m quite new to this bushcraft stuff. I still call it by something other than bushcraft. At any rate, I am primarily a cyclist in the bush. I cycle in the Appalachians of Pennsylvania on old railroad beds through all four seasons. I sometimes stop and sit for hours halfway through the ride, so this is what I’m basing my experience on. In other words, I do what every survivalist says is a no no. I go out, get super sweaty by exercising, and then I rest in below freezing weather. So far, with treatment like this, wool’s been the only fabric that’s able to perform well, so I’d recommend some merino wool long johns.
Unfortunately, it’s more expensive. I just bought some of the cheap stuff, and it was 40 – 45 dollars. It’s also a bit delicate. It’s got to be gingerly put on similar to a pair of women’s panty hose. I buy the stuff skintight because I want it to wick. For now, I’m using the Terramar woolskins base layer. My Terramar’s have developed a few rips here and there, but nothing unusual considering I get stuck by nasty thorn bushes quite a lot when I’m dressed lightly. Terramar’s always hold their repairs for me when I stitch them up. They’re made in China.
After the base layer of lightweight merino wool, I wear “Wool Power” thermals in the 200-gram weight. That right there keeps me comfy well into the low 30s while cycling or sitting. They also make 400-gram as well as higher weight fabrics. Wool Power’s thermals have a terrycloth weave, they’re made in Sweden, and it’s quite expensive.
I’ve cycled and trekked about in the woods with temperatures down to –20 on occasion and 0 Fahrenheit quite often. I always stop along the way and poke around in the woods or sometimes I just sit and watch stuff happen in the bush after getting very sweaty.
I also wear merino wool boxer briefs year round, and in the summertime, I wear kaki 100% merino wool tee shirts. They keep me cool when it’s hot. For me, wool’s the only material that I’ve found that maintains homeostasis just like it was my own natural hair, which I have little of... Thin wool shirts keep me comfy in 60-degree weather up into the 90s. For me, wool seems to have a 30 – 50 degree comfort range. With the thin base layer and an outer wind breaking shell, I’m comfy in the heat of home and also outside in lower 40-degree weather.
I’m sorry that I’m so verbose, but I like to explain what gear I use, how I use it, and what my level of experience is.