How to Choose a Base Layer

An appropriate base layer is one of your key layering pieces when dressing for outdoor sports. This layer has one major and important function: to draw moisture away from your body and to the outside of the fabric where it can evaporate, and keep you warm or cool depending on the outside temperature.  Cotton does not do this – so your first move is to ditch your cotton layers for a moisture wicking base layer.

Learn more how to layer clothing, in our recent article.

Why wicking fabric is better than cotton

Helps transport moisture from your skin, dries faster, and reduces the risk of dangerous swings in body temperature.

How wicking works

Moisture wicking works by pulling sweat away from your skin.  It wicks it to the outer part of the fabric where it evaporates. See illustration below.


Wicking illustration


So what are your options? It depends on two things: the season, and your activity level.  In warmer months, you will likely want a short sleeve shirt to help evaporate sweat. However, when it’s hot out, you may want a light base layer that will protect your arms from the sun.

You can either choose between synthetic, wool or treated silk.

1.  Synthetic Fibres

Synthetic fibres are generally polyester or some kind of polyester blend. Some add nylon for improved abrasion resistance, or small amounts of spandex or elastin to give the garment some stretch.

The Patagonia Capilene

The Patagonia Capilene 4

Advantages of synthetic fibres

  • They feel soft against the skin
  • Are the fastest drying of all, they dry faster then both silk and wool
  • Moisture wicking
  • Abrasion and wrinkle resistant
  • Easy to care for
  • Cost: there is an abundance of choice of brands and some are very reasonably priced. They are in general quite a bit less expensive

Disadvantages of synthetic fibres

The main disadvantage of synthetic is the fact that they retain odour, and often can only be worn only once. In the backcountry, hardly anyone wears synthetic anymore for this reason.  Ever been in a backcountry hut with twelve backcountry skiers? You won’t want anyone wearing synthetic!

  • Odour
  • Susceptible to staining
  • Made of petroleum fibre (plastic)

Best Brands

Patagonia Capilene, Under Armour, Marmot, Mountain Hardwear, Polartec Power Dry, REI, The North Face, ExOfficio.


2.  Wool Fibres

Merino wool has virtually replaced all traditional wool thanks to it’s super fine fibres. Unlike traditional wool, superfine merino wool is soft and comfortable against the skin. Another great advantage of these fabrics is they allow you to stay warm when wet – a property unique to wool is that it releases as it absorbs water. Energy, in the form of heat, is produced through the work of moisture absorption of the wool fibre.  Hence it humid or wet conditions, provides the wearer with an additional amount of comfort. This is in addition to the countless warmth-trapping air pockets created by all the crimps inherent in merino wool fibres.

icebreaker copy

Icebreaker Merino wool

Forget everything you remember about itchy wool, it’s lo longer the case.

Advantages of merino wool fibres

  • Lightweight, very soft and natural-feeling on skin, non-itchy
  • Does not retain odour. Can be used for days on end without stinking
  • Stays warm when wet
  • Wrinkle and stain resistant
  • Natural fibre: you feel the difference of natural fibre on your skin versus a polyester layer
  • Machine washable

Disadvantages of merino wool fibres

Aside from a higher price, the main disadvantages of wool is that it doesn’t dry as fast as synthetic, and is vulnerable to shrinkage.

  • Dries slower than synthetic fibre, though even when wet it still feels dry on skin
  • Cost
  • Vulnerable to shrinkage. Do not throw these in the dryer – hang them to dry.

Best Brands

Icebreaker, SmartWool, Patagonia, Ibex.

3. Silk Fibres

Silk base layer from REI

Silk base layer from REI

Advantages of Silk Fibres

Silk, which for performance use is a ‘treated’ silk – chemically modified to perform better moisture wicking, is generally used for cool and cold weather endeavours.

  • Silk has a soft, luxurious texture
  • Thin, non bulky, and great for layering
  • Natural fibre

Disadvantages of Silk Fibres

  • Need delicate care: most require hand washing, as machine washing generally shrinks them
  • Sensitive to abrasion and fade in sunlight
  • Tend to smell, and should be washed after every use.

The Bottom Line

When you weigh all the pros and cons of each fibre, you really can’t beat merino wool. It does everything better, and though it is a little more costly, it lasts longer and doesn’t need to be replaced as often. You don’t need to wash them as often meaning its better for more days out there – your friends will like you on backcountry trips if you don’t smell!

Where to Buy

Base layers are sold everywhere.  Use our outdoor gear finder to find the best price.



Alicja is an economist, enjoys climbing, mountaineering, backcountry skiing, cycling and gets out into the backcountry as much as possible. See all of Alicja's Blog Posts