Thermal Underwear Explained: Choose the Right Base Layer for Warmth and Comfort

When people hear "thermal underwear," many imagine something extremely warm — like a magic suit that protects you from any cold. But in reality, this type of clothing is more about performance and layering than miracle fabric.

Thermal underwear — also known as a base layer — is the first layer of clothing you wear in cold conditions. It helps regulate your body temperature and manage moisture. This layer plays a key role in both everyday winter wear and intense outdoor activities.

Types of Thermal Underwear

1. For Active Movement (Moisture-Wicking Base Layers)

If you’re skiing, snowboarding, winter hiking, or working outdoors, your body generates sweat. Wearing cotton is risky — it absorbs moisture and keeps it close to the skin, making you cold fast. Instead, look for synthetic thermal underwear with moisture-wicking properties.

This type of base layer pulls sweat away from your skin and dries quickly, keeping you warm and dry. For best results, it should fit snugly without restricting movement.

2. For Everyday Warmth (Insulating Base Layers)

If you’re heading to work, walking in the park, or spending time outside in winter, comfort and warmth are the priority. The best choice here is Merino wool thermal underwear. Merino is breathable, naturally moisture-wicking, and offers excellent insulation without the itch.

The warmth depends on fabric weight: 160 g/m² is ideal for mild cold, while 220 g/m² or more is great for harsher weather.

Final Thoughts: How to Choose the Right Base Layer

Thermal underwear doesn’t generate heat — it helps retain the heat your body produces. So the key question is: Do you need to stay dry during activity, or stay warm during stillness? Answer that, and you’ll know whether you need a moisture-wicking or insulating base layer.

No matter your goal — comfort, warmth, or performance — choosing the right base layer is essential for cold-weather adventures.

Explore our full base layer collection to find the best option for your next adventure.