What Is the Warmest Material for Thermal Underwear?

Best thermal underwear is often made from wool or silk, but it's important to get high-quality wool for optimal warmth. Cheaper wool tends to itch, but merino wool has incredible thermal properties. In addition to its natural warmth, merino wool doesn't have a flammable odor.

Cotton

Thermal underwear is made from different types of materials that can help keep the body warm. Cotton is the warmest of these materials, although synthetics can be equally comfortable and durable. Cotton is a breathable, lightweight material that can keep you warm during the coldest months. Microfiber is another option for thermal underwear. Microfiber is more form-fitting than cotton, and both materials are able to keep their shape even after repeated washings. If you decide to wash your thermal underwear, be sure to wash it in cold water to avoid shrinkage. In addition, you should lay it flat to dry faster. Avoid hanging it up to dry, as this can stretch the fabric and lose its shape.

Wool is another natural choice for thermal underwear. It is odor-resistant and hypoallergenic. Compared to cotton, wool is also breathable and doesn't collect moisture. It's another great option for people who have sensitive skin.

Merino Wool Blends

Compared to other fibers, Merino wool offers the most comfort and warmth for thermal underwear. It has a high level of thermal regulation and retains its insulating capacity even when it's wet. It is also softer and less itchy than other types of wool. However, it is not as lightweight as synthetic materials.

Merino wool is an exceptionally soft, breathable, anti-static and naturally warm fiber. It regulates temperature, keeps the wearer dry, and is odor-resistant. It is naturally warm and can be worn in layers, making it ideal for both base layers and midlayers.

Merino wool base layers from thermals should fit snugly next to the skin. Merino wool base layers are for extreme cold and thin enough to wear alone, but still warm enough to keep you warm on 40-degree days. A thicker midlayer should be worn over the base layer. This layer keeps you warm during colder temperatures and is best used for low-impact cross-training days. If you're wondering about buying silk thermals, check out our article to find out is silk thermals the best.