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How to Choose Ski Base Layers & Long Underwear

What is a base layer and why do you need to wear one?

A base layer is an insulating layer worn next to your skin. Base layers help regulate your body temperature by  moving perspiration away from your skin, which will help keep your dry. Staying dry allows you to stay warm and happy in the winter. Base layers come in many forms, from t-shirts to leggings, tights, briefs and sports bras. Some are designed to contour to your body while others are more loose fitting. Base layers also come in different weights or thicknesses to suit different temperatures and activity levels. Learn more about baselayer "weights," what baselayers are usually made out of, and differenet baselayer styles below!



Baselayers are loosely organized into light, mid and heavy weight categories based on the fabric's weight per square meter (or sometimes ounce per square yard). Every brand has different cut offs for what light, mid and heavy weight actually means, so take this classification with a grain of salt!

Lightweight | <200 grams/M²

This is a thin first layer that goes next to your skin with the ability to easily add layers over it. Lightweight base layers are a crucial step in layering as they must be comfortable on the skin and are designed to fit tighter for the best moisture management. Worn alone, they are best suited for mild to cool conditions with high levels of activity like running, climbing, cross-country skiing, touring etc.

Midweight | <270 grams/m²

A midweight layer can be worn as a warmer first layer or as a second layer over your next-to-skin layer, providing a combination of insulation and moisture wicking. Alone, it is best suited to cool or moderately cool to cold conditions with medium levels of activity where you will be moving some of the time but standing still at others. It can be combined with lightweight layers underneath or heavyweight layers over it to accomplish the desired warmth.

Heavyweight | 250 grams/m² +

This is designed for cold conditions combined with any level of activity and often referred to as "expedition or thermal weight." Almost always worn over a lighter weight layer, heavyweight layers are designed to add insulation and are worn looser with less focus on moisture management. These layers are thicker due to their higher loft for insulation.


The majority of base layers in today’s world are composed of Merino Wool, synthetic fabrics like Polypropylene, or a blend of the two. Rather than absorbing moisture, these fabrics wick (transport) moisture and perspiration away from the skin and disperse it on the outer surface where it evaporates. Both of these fabrics do roughly the same things: efficiently transport moisture away from the skin, dry much faster than conventional cotton and reduce the risk of dramatic swings in body temperature.

Synthetic vs. Wool

SyntheticMerino Wool
  • Soft
  • Easy care
  • Lightest base layer
  • Abrasion-resistant
  • Wrinkle-resistant
  • Very stretchy
  • Excellent moisture management
  • Excellent drying time
  • Soft
  • Stain and wrinkle resistant
  • Natural fiber
  • Excellent moisture management
  • Excellent temperature regulation
  • Excellent odor resistance (it doesn’t stink)
  • Very good stretch
  • Slightly less effective temperature regulation
  • Odor can build up if not consistently washed
  • Petroleum-based synthetic fiber
  • Potentially vulnerable to staining
  • Slower drying time than synthetics
  • Potentially vulnerable to shrinkage if not washed properly
  • More expensive than synthetic base layers



Long sleeved base layers are most commonly used for colder conditions and are often paired with additional layers in order to maximize warmth. Short sleeved base layers tend to be used in hot to warm to cool conditions where moisture wicking is more important than heat retention and wearing just a short sleeve base layer is enough.


Base layer bottoms come in two styles - the more traditional full leg or the increasingly popular 3/4 leg for use speficially with ski or snowboard boots where the bottom ends where your boot begins to avoid clumping.


One piece base layers are the ultimate in base layer protection. They seal out any drafts and cover the majority of your body, making for a perfect base layer in cold conditions. Some one piece base layers even have a hood because 40% of your body heat can “escape” through your head.

Remember, all base layers are designed to perform whether worn alone or with other layers. Although it may take some getting used to, adding or removing layers is the optimal way of regulating your temperature and moisture in cold weather, especially during physical activity!

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