Ideal thermal underwear for hiking, winter climbing Elbrus and Kazbek?

Very often our clients ask us the question: what kind of thermal underwear is better to take on a hike in the Caucasus in the summer or what kind of underwear is needed for climbing Elbrus in the winter and how many sets should you take with you.

First, let's figure out what thermal underwear is and its purpose and concepts.
What is thermal underwear?

It is correct to say “functional underwear”, since the main task of “thermal underwear” is to carry out the function of removing excess moisture from the body during intense exercise. Although, there are sets of underwear that are specifically designed to retain heat, but they have a different functional purpose.
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How it works?

Functional underwear/thermal underwear (hereinafter referred to as thermal underwear) has a certain fabric structure and its fibers, which are designed in such a way that when moisture appears on the human body, it comes out freely. The key word is “unobstructed”... Ideally, of course, this happens, and most of the moisture is transferred out of your clothes. But the percentage of final moisture removal from your body depends on several parameters: the structure of the fabric, the intensity of the load, the temperature and humidity of the environment, and an important point - the natural circulation of air around your body.

Let's look at each point separately.
Fabric, fiber structure

I will not list numerous manufacturers. The first thing to note is that thermal underwear with maximum removal of moisture and excess heat from the body is always made of synthetic fibers and the addition of a small percentage of wool or cotton fibers produces a fabric that is pleasant to the touch and for the body. And here, of course, it is worth noting that thermal underwear with a large amount of wool or warming synthetic fibers is intended more for active types of recreation - such as fishing, hunting, or for winter mountaineering, ice climbing and conditions close to winter mountaineering, where the load is variable (there is periods when you stand at belay points and wait for a partner, etc.). That is, when choosing thermal underwear, it is worth determining its functional purpose.
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Definitely, I cannot recommend completely woolen underwear and a combined option (synthetics with added wool is ideal) for skiing and mountaineering in winter, hiking in the mountains. For confident skiers who ski quickly, it is better to have two sets of thermal underwear - woolen and synthetic, and wear them based on the air temperature. For summer ascents and hikes in valleys and approaches, I recommend exclusively synthetic thermal underwear. During the period of climbing passes and peaks, you can wear a thermal underwear top with wool additives or a completely wool top. For everyday wear - underwear with the addition of natural cotton or silk.

Among the manufacturers of wool-based thermal underwear, we can note: Icebreaker wool thermal underwear, as well as Craft and Montane thermal underwear with the addition of wool.

An important point is that inexpensive domestic manufacturers work just as well as imported ones. But the fabric in them is cheaper, the cut is not always ergonomic and not so pleasant to the touch, and it quickly acquires an unpleasant odor. Of course, it’s hard to compare them with top manufacturers, but the price of X-bionic is 5-7 times higher than domestic ones. It’s good when thermal underwear has silver inserts, which allows you to maintain a fresh smell for several weeks and there is no need to wash your clothes every day while camping.
Load intensity

The intensity of the load on fishing and ice climbing, and on a mountain hike in the Caucasus, and on climbing Elbrus and Kazbek in winter or climbing the Matterhorn are completely different. Since the fisherman stands most of the time, you can safely take completely fleeced underwear, which is not permissible on a mountain hike, where your back under a backpack constantly sweats while moving and if you have warm wool underwear, it simply will not have time to remove moisture and dry at rest stops. What cannot be said about mountaineering, where there is a part called approaches and a part with variable load - climbing, when the athlete passes difficult sections and then waits for a long time for a partner or group, or vice versa, a partner waits at the station while his friend passes a difficult section. And here, of course, the best option is underwear with wool inserts or expensive wool-based underwear. Synthetics can be used on the approaches. To climb Elbrus and Kazbek in winter, be sure to take woolen thermal underwear, the rate of ascent is low most of the time, and you don’t have time to sweat...
Environment and outer layer of clothing

You need to understand that no one can guarantee 100% moisture removal if the air temperature is more than +25 C and you sweat simply because you have to sweat at this temperature, even without performing certain loads. The only question is that the fabric that begins to absorb moisture must dry instantly so that discomfort does not arise. And here, of course, synthetics are ahead of natural fabrics.

The next point worth paying attention to is the outer layers of clothing. In the 21st century, outdoor clothing technology is actively developing. Main pr

The principle of functional clothing is layering. The number of layers is determined by the ambient temperature, air movement speed, humidity, and the presence of precipitation.

Let's consider an example of clothing for temperatures of +0 C....+15 C. The principle of operation of the multi-layer structure of clothing in this case is the bottom layer, the layer that is closer to the body (“thermal underwear”), removes excess heat and moisture outward, the intermediate layer (“fleece” or “Polartec”) acts as a conductor of excess moisture, as well as an intermediate heating layer that allows you to retain heat. The outer layer is a membrane fabric, which, again, removes excess moisture and heat, but does not allow moisture and wind to pass inside (Windstoper only protects from wind, but at the same time breathes like a membrane).
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Depending on the temperature and air speed, a combination of additional layers is possible.

Therefore, it is important that your thermal underwear is worn together with other layers of functional clothing, and not under your grandmother’s knitted sweater, and on top of a canvas jacket or rubberized raincoat. Well, again, thermal underwear cannot be all-season and universal.