Winter thermal underwear
Which is the best thermal underwear?
Simple, not quite.
When dealing with life in the open air with temperatures below zero, we must keep in mind several factors, the first internal ones, therefore due to ourselves and to our physical composition and habit of the cold, in a nutshell “how cold are we?” The other factors are due to the choice of the layers we will use to cover ourselves.
The first layer called “skin” or “base” has to do the bulk of the work. In fact, the winter thermal underwear must keep the heat, letting the water vapor produced in activity evaporate, but also keep the heat when wet to avoid cooling.
At this point we go by exclusion, the cotton transpires is comfortable and warm if combed, as long as it is dry and here is the problem, which makes it absolutely not recommended, when the cotton is wet it disperses the heat, so it becomes cold! In cold and humid conditions, it leads you to hypothermia. So cotton is not recommended.
The synthetic thermal underwear (polyester, polyamide, polypropylene and their mix) removes water vapor, keeps part of the heat, so far so good, not being natural it could irritate the skin (it is basically plastic), it stinks quickly, it melts in case of fire.
Thermal or better thermoregulating merino wool underwear is comfortable for a long time, even weeks, thanks to its natural composition (it is keratin like our skin), it transpires and thermoregulates even when completely wet, it does not irritate and works (depending on the weight) at all temperatures, plus it is fire resistant. So the best winter thermal underwear and not only is merino wool.
Wool is also an excellent insulating layer (second layer) both pure and mixed with a low percentage of synthetic fibers. Helps convey water vapor and traps heat.
The third layer or shell is the one that protects from wind, rain and snow, but to work well it must also allow the water vapor carried by the previous layers to escape, so whether it is synthetic (membranes) or natural (Arctic cotton, Ventile, wool), it must be breathable!