What is Base Layer Clothing?

What is base layer clothing heat ultra family thermal underwear

Before organizing outdoor activities, you need to ensure that you are equipped with the right clothing for the exercise and any possible weather changes. Base layer clothing (thermal underwear/clothing) should always be the foundation of your layering strategy, especially during the colder months. 

You may be wondering, "What are base layers?" If this phrase sounds strange to you, then you likely have been layering all wrong. In this article, we explain thermal underwear and go into detail on related questions you may have.

Thermal Clothing Explained?

A base layer is the clothing layer that is in direct contact with your skin and serves as a consistent "두 번째 피부" during the day. Also called long underwear, they add a layer of insulation while soaking up and releasing moisture, keeping you comfy.

Base layers are adaptable clothing that comes in various materials and designs, each with its own set of advantages that are best suited to the wearer, specific climates, and situations. 

Types of Base Layers

Base layers and thermal clothing are usually divided into two types: tops and bottoms, which can be worn alone, beneath another garment, or as a component of a layering strategy. Here, we go over each piece from top to bottom.


A thermal top is essential in both summer and winter. Regardless of the outdoor activity you engage in, long underwear is an excellent option for the cold. Longer sleeves facilitate blood flow, and this protects you from cold weather.

Before choosing a style, think about what you'll be wearing on top of your base layer. Are arm warmers included in your mid-layer or jacket? This element may influence your decision to wear a base layer with a shorter sleeve length in the winter.


Long underwear bottoms are ideal for conducting extra warmth beneath your pants when you conquer the outdoors or as a solo layer for jogging.

Bottoms, also known as thermal leggings, are versatile pieces of clothing that you can use for everything from skiing and biking to walking and jogging. If you're very cold, you may even wear them beneath your slacks or work clothes.

How to Choose Thermal Wear

When it comes to selecting the best thermal underwear, you need to consider the following:

  • Fabric

The fabric you choose is the most crucial selection you'll make. Whether you choose a synthetic or natural fabric, it must wick properly (move sweat off your skin).

  • Weight

It's basically "lightweight," "midweight," or "heavyweight," with thicker textiles adding a layer of warmth.

  • Fit 

When putting on long underwear, make sure it fits snugly against your skin while allowing you to move about freely. This is because to accomplish its function, wicking fabrics need to be in direct touch with your skin. 

Heat Ultra, Your Choice for Winter Thermal Wear

Heat Ultra presents the latest in innovative fabric design for you and your family. Layer up this winter with our ultra-fine micro acrylic that creates compact, lightweight fabric for unbeatable insulation.