The Main Misunderstanding

Thermal underwear does not warm you by itself. Its task is to remove moisture from the skin and create a thin layer of air close to the body. The warmth is retained by the following layers of clothing. That is, it is not a replacement for a sweater, but a base underneath it. Because of this, a person who puts on thermal underwear under a thin jacket and goes out into the cold will freeze just as they would without it, and sometimes even faster, because this fabric itself is very thin. The working system consists of three layers. The first removes moisture, that is, thermal underwear. The second retains warmth, that is, fleece or wool. The third protects against wind and precipitation, that is, a jacket.

Removing any layer from this system means completely breaking it.

The Second Misunderstanding, That Is, Activity Instead of Temperature

Most people choose thermal underwear based on the frost, whereas it should be chosen based on the level of activity. The logic here is as follows. During movement, the body produces heat and sweat, and the main task becomes removing moisture, because wet fabric against the skin takes heat away faster than any frost. When at rest, almost no sweat is produced, and the main task becomes retaining heat. From this follows the rule. For high activity, that is, for running, skiing and work that makes you sweat, synthetic fabric is needed, because it removes moisture best and dries quickly. For low activity, that is, for walks, waiting for transport, working in a cold room or staying at home without heating, wool works better, primarily merino wool, because it is warmer. For medium activity, combined models that combine both materials are suitable. This is exactly where most disappointments arise. A person buys thin sports synthetic underwear to stand in it at a bus stop, and freezes. Or buys dense merino wool for a run, sweats and also freezes.

What This Means for Our Conditions

It is worth separately mentioning a scenario that does not appear in foreign advice. Thermal underwear at home with the heating turned off is one of the most effective ways to retain heat, and I wrote about this in the material about a cold apartment. But this is exactly low activity, that is, you are sitting, working at a computer or reading. Therefore, for this scenario, you need not sports synthetic fabric, but wool or a combined option, and preferably a denser one. This is the detail because of which people buy the wrong thing and then believe that thermal underwear does not work.

Types by Material

Synthetic thermal underwear is made from polyester, polypropylene, polyamide with the addition of elastane. It is the most common on the market, removes moisture well, dries quickly, is resistant to abrasion, does not deform after washing, does not attract moths and costs less. Its main disadvantage is that it accumulates odor, so it has to be washed after every wear. Woolen, primarily made from merino wool, is considered a premium option. Wool fibers retain heat better due to their structure, breathe well and hardly acquire odor, so it can be worn for several days in a row. Its disadvantages are the price, slower drying and the need for delicate care. Combined thermal underwear combines both materials, with the inner layer usually being synthetic and responsible for removing moisture, while the outer layer is natural and responsible for warmth. This is a universal option for everyday wear. It is also worth mentioning cotton separately. It absorbs moisture well and dries very slowly, so as a first layer in the cold it works against you. Products with a predominance of cotton are not thermal underwear in the functional sense, even if that is written on the label.

Density

This parameter is indicated in grams per square meter, and it determines warmth. For merino wool, the guideline for cold conditions is approximately from two hundred to two hundred and sixty grams per square meter. Lighter options are suitable for activity and the off-season, denser ones for frost and for prolonged periods without movement. If the manufacturer does not indicate the density, this is already a certain signal about the level of the product.

Fit and Seams

Thermal underwear should fit closely to the body, but not press or interfere with movement. If it hangs like it is on a hanger, there will be no effect at all, because an unnecessary volume of air forms between the fabric and the skin, and the fabric stops contacting the skin and removing moisture from it. Because of this, the common habit of taking a larger size for freedom destroys the very function of the garment. The seams should be flat, preferably external, without protruding threads, because during movement rough seams rub against the skin. Seamless models are a separate category, and for prolonged wear they are more comfortable.

How to Wear It Correctly

It should be put on bare skin, and this is not a stylistic recommendation, but a condition for it to work. There is an important nuance here. If you leave underwear underneath it, it should also be synthetic, not cotton. Cotton under thermal underwear will absorb moisture, will not dry, and you will spend the day in wet clothing. Do not wear thermal underwear as a separate item of clothing without outer layers, because it is not designed for this. Do not put non-breathable clothing over it, because the moisture removed from the skin has to go somewhere. If the next layer does not let it through, it will accumulate inside the system, and the effect will be the opposite. Do not put several sets of thermal underwear on top of each other, because this does not double the warmth, but only increases the thickness of the first layer.

Care That Extends Its Service Life

The rules differ depending on the material, but several are common. The washing temperature should not exceed thirty degrees for synthetics and forty for the rest. A tumble dryer should not be used. Ironing is also not recommended. Fabric softener and products with bleaching agents should not be used, because they clog the structure of the fibers, and this is exactly why a new-looking garment stops removing moisture. Synthetic fabric can be washed in a machine on a delicate cycle or on a sportswear program. Merino wool is better washed by hand in cool water without aggressive detergents, because machine washing damages it.

It should be dried in a spread-out position, not on a radiator and not under direct sunlight.

What Not to Do When Buying

Do not rely only on the word thermal underwear on the label, because it is not protected and is written on any close-fitting underwear. Do not buy cotton sets for cold weather. Do not take a size larger. Do not choose based on the temperature range on the package, because it is conditional and does not take your activity into account. Do not save on children's sets by choosing cotton, because children move unevenly, meaning they sometimes run and sometimes stand still, and wet cotton cools them down the fastest.

How to Check It After Buying

The simplest test is to put on the set and spend an hour in it under conditions that are normal for you. If you immediately feel cold or, on the contrary, hot and damp, the material removes moisture poorly or does not breathe well. The correct feeling is an even, comfortable warmth without a greenhouse effect.


Sources

Publications by ZAXID.NET based on materials from Hotline, Ukrainky.com.ua, Shambala, Alp.com.ua, Issa Plus, materials on thermal underwear care