Think of base layers—aka long underwear or long johns—as the foundation for your cold-weather layering system. Choose them wisely, and you’ll stay warm and dry whether you’re cross-country skiing, winter camping, or skiing and riding in a resort. Choose poorly, and you might be drenched in sweat or shivering (or both!), no matter what else you’re wearing. Base layer tops can be worn alone or under a shell or insulated jacket, while bottoms are almost always meant to go under soft-shell or hard-shell winter pants (though some can double as standalone leggings).
Base layers come in a variety of different materials and weights, each best suited to a particular kind of winter recreation. Here’s how to choose the best base layers for all your activities.
In this article, you’ll learn:
- The pros and cons of different base layer materials
- How to choose the best base layer thickness
- What base layer features to consider
One of the biggest base layer shopping decisions goes right down to the fibers used. Generally, base layers can be sorted into two camps: natural materials (primarily merino wool, but also plant-based rayon and hemp) and synthetic materials (polyester, nylon, spandex).
Wool & other natural materials
Let’s get one thing straight: Today’s wool is not itchy. Made from ultrafine fibers sourced from Merino sheep, merino wool is soft and comfortable against the skin, never abrasive. And some of the plant-based natural materials, like bamboo-derived rayon or wood-based lyocell or modal, feel even cushier. Other reasons to love these fabrics: They’re breathable and great at moisture management, wicking sweat away fairly quickly. Though wool retains moisture within its fibers, it still feels dry against the skin. And merino wool is naturally antimicrobial, preventing the growth of odor-causing bacteria for an impressively long time.
On the con side, merino wool isn’t as durable as synthetic fabrics, and often pills with abrasion (like under pack straps). It’s slow to fully dry and tends to be the most expensive option.
Worth noting: Some wool production has been associated with mistreatment of the sheep that grow it. In response, some brands have developed standards for their suppliers to ensure the humane treatment of the sheep and systems to trace their wool back to the ranches for accountability.
The typical synthetic fabric is made from polyester or nylon, often with a bit of spandex added for stretch. These fibers excel at wicking and drying quickly. They’re more durable than natural fibers, and usually cost less. But they’re notorious for getting stinky fast (some have anti-odor treatments, which help). Synthetic fabrics are also derived from petroleum, but more brands are using recycled fibers to reduce the environmental impact of their layers.
Blends & combinations
Some base layers use both natural and synthetic fibers to take advantage of the best qualities of each. One common construction sandwiches a synthetic layer to a wool layer—one on the inside, one on the outside—to deliver fast wicking with odor control. Another wraps a wool fiber around a nylon core for added durability.