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What Material is Thermal Underwear?

What Material is Thermal Underwear?

If you are new to thermal underwear, you probably don’t have a lot of information about the differences between different aspects. One of the most critical things to consider when purchasing thermals is the fabric that comprises it. After all, the fabric plays a major role in your thermals performance. The reality is that while most thermals are either wool, synthetic, or a blend of both, there are also options that involve cotton or silk. In other words, when it comes to fabric, there is great diversity. Let’s take a look at each material.


Sheep often live in cold climates and can weather fairly significant weather. Thus, it is not surprising that their coating is used for thermal underwear. Wool thermals are excellent for protecting your warmth. They also tend to be comfortable and are fast drying if exposed to moisture. There is a possibility that wool can be scratchy, but this is typically only if you purchase thermal underwear made from low quality wool.


Synthetic thermal wear is made from manmade fabrics such as polyester, nylon, spandex, and other fibers. These fabrics are often employed for active wear due to their moisture wicking abilities. They also tend to be quite comfortable and excel in heat retention. Another benefit of these are that they are easy to care for, typically being able to be both machine washed and dried.


Cotton has many benefits for clothing; however, these do not all translate well to the world of thermal underwear. The primary benefit of cotton is that it is relatively inexpensive. However, it also stands up less to cold weather than other options. Cotton particularly tends to retain moisture, which can lead to temperature loss. It also tends to shrink if you accidentally throw it in the dryer. Cotton is great for people spending short amounts of time outdoors.


Silk thermal underwear is probably the type you are least likely to find. However, it does have some benefits. Namely, it is good for light activity snow sports as well as lounging inside. Silk is very comfortable. However, silk also tends to be among the most expensive and it will not have any moisture-wicking properties.


Blends tend to primarily be a combination of wool and synthetic materials. This can be beneficial as it helps incorporate the best properties from each material. These options can be great for virtually any outdoor activity.

Final Thoughts

Ultimately, thermal underwear consists of many different materials. Typically, wool is thought of as the best while synthetic fibers are a very close second. Understanding how thermals protect your core is important when choosing the right material.

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