How to Choose a Base Layer

In any situation, if an issue arises, it's always best to get to the root of the problem. This is certainly true when it comes to layering your cold-weather clothing for hiking, climbing, skiing, snowshoeing, and other wintertime sports, with the proper base layer setting the stage for the rest of your garments.

Layering Theory 101

The best way to protect yourself from the elements is to wear three separate layers—a base layer worn against the skin, a middle layer, and an outer layer. Each has a unique purpose, and if worn properly, all layers work together to wick sweat away from your body, hold in heat, and keep out wind and rain

How should your base layer fit?

In order for a base layer to wick properly, the fabric needs to lay against the skin in order to pick up moisture. To enable this, the fit should be relatively snug. An exception to this is if you are wearing the garment with no additional layers in warm weather. Some runners and hikers prefer a lightweight, loose fitting synthetic tee that allows for better air flow.

What is wicking?

All base layers should be made from wicking materials. These special fabrics draw sweat away from the body, pushing moisture to the middle and outer layers. The surface area of wicking materials is considerably greater than that of fabrics like cotton, making it easier for moisture to evaporate, which in turn makes the wearer, you, feel warmer and more comfortable.

In regards to cotton, avoid the material as a base layer at all cost – at least in colder temperatures. Cotton has virtually zero wicking capabilities, and is prone to absorbing and retaining heavy amounts of moisture. Sweat the slightest amount and you'll spend the duration of your outdoor adventure lugging around the soggy albatross that has become your cotton base layer.

Temperature control Winter activities are exceedingly strenuous. Unfortunately, a side effect of extended cold weather exposure is that your muscles weaken and become more susceptible to injury. Base layers are meant to keep your core muscles warm. However, base layers can also be used to keep you cool. Many loose-fitting, lightweight fabrics are designed to target and evaporate warm sweat from the body, while encouraging air flow to keep you feeling cool in warm temperatures.

Base layer weights

With every season comes a new roster of outdoor activities that demand a certain attire. Base layers come in all shapes, sizes and, most importantly, weights to accommodate the various activity levels and temperatures.

Lightweight: As a rule, the thinner the fabric, the better it wicks and the faster it dries. Most outdoor athletes prefer a light layer against the skin, even though it provides minimal insulation. In winter, a Nordic (cross country) skier may opt to combine base layers by wearing lightweight shirt under a midweight or heavyweight piece. Look for a snug that also feels good against the skin, like EMS's Techwick lightweight crew shirt. While lightweight layers are designed to be part of a layering system, they can still be worn as standalone pieces in mild to cool conditions so long as your partaking in a high-level activity, such as running.

Midweight: These bases will commonly act as a first next-to-skin layer, but may also serve as a second layer over a lighter material. Providing both insulation and moisture wicking, midweight materials, such as Under Armour's Base 2.0, blend well with layered outfits, while also providing protection moderately cold temperatures when combined with medium levels of activity.


The name kind of says it all. Heavyweight materials are designed for cold conditions no matter how sedentary or intense your schedule may be. Not typically worn as a first layer, heavyweight bases tend to accompany lighter materials, adding pure insulation. Their wicking properties are few because moisture management isn't a priority. Heavyweight materials are thick and typically fall loosely on the body.


There are four primary materials that are used to make base layers:


Commonly made from nylon, polyester or a polyester blend, synthetic materials are perfect for snug fit that feels good to the skin. They're almost exclusively wicking capable, and assist in resisting both wrinkling and abrasions.


Traditional wool is still used to fashion base layers, but the older fabric has essentially been replaced by merino wool - used in Smartwool - which features exceptionally soft fibers. Wool is lightweight and soft to the skin. Unlike synthetic materials, however, wool relies more on moisture absorption than wicking. A base layer of merino wool is capable of holding 30 percent of its own weight in water absorption before the wearer is able to feel it on their skin. Even while saturated with sweat, wool's unique fiber construction allows the material to remain breathable, proving wonderful temperature regulation and odor resistance.


Usually treated with chemicals to enhance wicking properties, silk is a specialty fabric designed for use in colder temperatures. It's notoriously soft thread makes for an unbeatably smooth texture, which feels great on skin.



Comfortable on skin Lightest materials Wicks moisture Resists abrasions and wrinkling Easy to care for Elastic Quick drying time Affordable


Offers little odor protection (unless treated) May hold stains Slower temperature regulation than wool Petroleum-based fiber


Pros: Lightweight Comfortable on skin Resists stains and wrinkles Resists odors Made from natural fibers Elastic Exceptional moisture management Exceptional temperature regulation


Slow to dry Can shrink if not properly washed Prone to moth damage if not properly stored Typically more expensive than other materials



Soft texture Comfortable on skin Made from natural fibers Thin and very lightweight Wicks moisture


Hand washing often required Can shrink if not properly washed Vulnerable to abrasions Vulnerable to sunlight Not as durable as synthetic materials

Layer for Your Activity

Extreme Adventures:

Odor resistance matters, especially on long trips. Hiking, climbing, snowshoeing for hours at a time is going generate sweat and synthetic materials will begin to sweat as your trip goes on. Try to stick with wool as your go-to base layer during intense outdoor excursions. The material has a natural odor resistance, as well as a unique ability to hide dirt and grime. Wool's combination of thick insulation and breathable absorption make it the perfect option for keeping dry while you're staying warm.

Recreational Snow Sports (Skiing or Snowshoeing):

As mentioned earlier, activities that require you to trudge through snow banks and harsh landscapes are going to burn more calories, so it's imperative that when you're out on the slopes or snowshoeing over a snowy ridge you remember to layer thoroughly. Begin with at least two layers and add or subtract according to your activity. Of course, always keep at least a single base layer on, preferably something thick and warm like wool – just make sure it's a snug fit. Your second layer can be looser wool or, perhaps, a synthetic material. It's never a bad idea to bring along a day pack for storing and shedding layers as needed.

Upper Body Activities (Climbing or Kayaking):

Using your upper torso, especially when climbing, will lead to lactic acid build up in your muscles which cause swelling. For you base layer, choose a thicker fabric with a looser fit, like some wool, especially in the armpit and chest areas. If you'd prefer a synthetic material, which would also acceptable protection, look for manufacturers who have altered seams to curb chaffing – typically referred as flatlock seams.


Finding a base layer for back packing means identifying a material that will match the versatility of your own adventure. If you expect to be in a wide range of climates, choose a material that is similarly suited - both synthetic and wool bases are preferred. Disregard your material's breathability, as the backpack is likely to trap in sweat regardless, but consider comfort and weight for the long treks. Wool's ability to absorb large amounts of moisture without become noticeably moist makes it the most welcoming option on extended trips.

Casual hiking:

Assuming the temperatures are cool to moderate, your base layer for a light hike should be form-fitting and warm. Nearly all of traditional base materials, with the exclusion of cotton - unless it's warmer weather – offer viable options. Bamboo offers moderate protection and extreme comfort. Silk is smooth to the skin and has exceptional wicking abilities. And both synthetic and wool bases offer maximum warmth and comfort.

Fabric Care

As with any fabric, base layers need to be maintained properly. Silk, because of its fine, delicate construction, makes care particularly challenging. Many garments will require hand washing, Like wool, machine washing silk runs the risk of shrinking the material.

Synthetic fabrics have little odor resistance, making regular washing a requirement. Unfortunately, special treatments and coating, which are common on synthetic fibers, make the material susceptible to damage from harsh detergents. The material requires most garments be hang-dried, but overall maintenance is fairly simple.

Keeping wool clean is a task in and of itself, but its versatility makes it worth the extra effort. The material must be washed cold water to avoid shrinking. Some manufacturers will claim their products are capable of withstanding a warm wash without being distorted, but it's a safe bet to use cold water any way. Wool doesn't respond well to either bleach or fabric softeners, and their reaction to a warm dryer is similar to that of warm water. Hang-drying wool is the only way to ensure the continued integrity of their shape and size.