How To Buy Baselayers

One of the most important pieces of any wilderness adventure and outdoor athletic kit, baselayers dry quickly, transport moisture away from the skin, resist odors, feel great, and last for many years. This all-important layer that is often not changed for days on end and acts like a second skin is no place to skimp. Our guide will help you learn how to choose the best baselayer for your needs.


Material: The choice of baselayer materials really boils down to two options: synthetic and wool. Both have advantages, various styles, and legions of fans. The disadvantages of both are few among top manufacturers.

Wool: Used for centuries in textile manufacturing, wool is proven as a baselayer. Most quality wool baselayers use some blend of merino wool as the main fabric component. This wool is sometimes blended with small amounts of polyester, spandex or other synthetic materials to enhance the properties of the shirt.

Merino Wool is treasured for its ability to dry quickly and resist odors.

Some merino base layers also use activated carbon additives such as Cocona to enhance the wool’s hydrophobic, quick-drying properties. An added bonus of activated carbon treatments is they tend to resist odors even better than merino wool alone.

Synthetic: Synthetic baselayer materials often rely on polyester as the main ingredient.

Many companies have proprietary polyester-based fabrics such as the popular Patagonia Cappeline. Other fabrics used by many companies are made by name-brand fabric suppliers such as Polartec and Scholler.

These fabrics are often similar across brands, so other features in the garment set one brand apart from another. Experienced users trust name-brand fabrics to work well under tough conditions.

Many polyester-based garments blend spandex or other synthetics into the cloth to add stretch.

Some synthetics include antimicrobial treatments to combat body odor.

Nicole Rock, Director of Design and Development at clothing manufacturer Isis, said a few factors help customers make the decision between wool and synthetic.

“Decisions can be made on price point. Merino can be a pretty big investment,” Rock says. “A lot of times depending on knit, construction and weight, synthetics may dry a little faster. If you have wool that gets wet, it still has good insulating properties.”

Eric Larsen, an Arctic Explorer who has been to the summit of Mount Everest and the North and South Poles in the same year, said he dresses in multiple baselayers in extreme cold

“I start with a very light layer of synthetic, then wool because it’s nice and doesn’t smell,” Larsen says. “On top, I will wear a fleece as well. For long, extended trips in extreme cold, I want all synthetic.”

Rock says many people choose wool for less demanding outdoor adventures for its softness and natural feel.


Weight: Baselayers are used in all weather conditions, from frigid ice climbing to blazing hot summer runs. Accordingly, they come in a wide range of weights.

Lightweight: Many people choose a lightweight baselayer, either a tee or long sleeve shirt, as the first layer against the skin regardless of the temperature. Lightweight baselayers wick moisture away from the skin and offer the bonus of versatility. Both synthetic and wool lightweight baselayers can be used in hot temperatures as a tee or under many other layers in the cold heart of winter.

Mid weight: A mid weight base layer can be worn against the skin or over a lightweight base as added insulation. Most mid weight bases are heavy enough to provide some warmth on their own, especially in conjunction with a light shell. These layers are popular as summer mountaineering shirts, around the camp at night, or as part of a winter layering scheme.

Heavy weight: Heavy baselayer garments are usually reserved for winter use. While they can function well in spring and fall as stand-alone shirts, they generally provide too much insulation for warm weather activities. Wearing heavy-weight baselayers close to the skin provides a wicking layer that dries quickly and also insulates against the cold.

Compression: Some base layers should be worn tight. These layers, called compression layers, work by reducing vibrations and lateral movements in working muscles to help reduce fatigue. Compression garments are popular among runners, cross-fit participants, and others who see a benefit from this type of muscle stabilization. Most compression layers are not suitable to be worn as winter base layers for sports like mountaineering, hiking, and downhill skiing where they will be worn for many hours or days on end.


Shirts: From tech tees worn year-round to heavy winter-wear, baselayers are popular shirts for all sorts of activities. They can be worn in a broad range of conditions and often are designed with fashion in mind.

Shirt features to consider are long zippers or buttons under the collar that can be opened to dump heat during aerobic exertion, thumb loops on long sleeve models and hoods, which can significantly add to the warmth of the layer.

Bottoms: Also called long underwear or long johns, modern base layer bottoms are a critical piece of gear during the winter months. A heavy weight bottom worn under a shell is often sufficient insulation for downhill skiing even on moderately cold days.

When choosing bottoms, also consider the weight of your other layers. Will you wear only a shell over the bottoms or do you wear an insulated shell pant? Insulated shell pants require much less additional warmth and a lightweight base will likely work in all but the coldest days.

A final thing to keep in mind when purchasing baselayer bottoms is style. Remember, there’s a pretty fair chance that they will be worn sitting around a fireplace with friends after a long day of skiing or riding.

One-piece: No, onezies aren’t just for babies! While not the most popular option, many companies do offer one-piece baselayers that cover the body from ankle to neck. The advantage of one-piece baselayers it there are no seams at the waist to bunch or bind. There is also no chance of a shirt slipping up and exposing a large area of skin to the elements during a fall or other unplanned tumble.

Antimicrobial properties: Most baselayers address body odor in some way or another. Most commonly, some type of antimicrobial treatment or additive precludes the growth of stink-causing bacteria.

While most companies treat their baselayers in some way, not all are created equal. It’s worth investigating the way the treatment is applied and how long it’s guaranteed to work. Some older treatments were known to wash out of garments over time. Most modern textiles are tested for antimicrobial properties through about 50 washes.

Examples of popular antimicrobial treatments are Gladiodor from Patagonia, Polygiene Active from Outdoor Research made from silver salts, and activated carbon like that made by Cocona and used by various manufacturers.

SPF and UPF: If you’ve worn sunscreen you know about SPF. However UPF is a slightly less seen rating used for garments. It stands for Ultraviolet Protection Factor. Many baselayers apply an additive to increase resistance to ultraviolet radiation. They will frequently list the SPF rating of baselayer shirts in the technical information of the product overview.

For reference, a thin white cotton tee will have a UPF about 4, while a dark blue cotton tee could be as high as 18. Looking for a UPF or SPF rating on outdoor oriented clothing guarantees a quantifiable level of protection.

Seams: Some tight fitting baselayers, and particularly compression layers, take seems into account during the production process to eliminate chafing.