How to Choose the Right Winter Base Layer

With winter just around the corner, choosing the right base layer can be key to enjoying the cold weather. A good base layer offers the right combination of insulation and moisture wicking and, despite a relatively hefty price tag, makes a worthwhile addition to any outdoor wardrobe.

The right materials

Forget about cotton; only wool or technical synthetic fibers make a good base layer. Merino is undoubtedly the king of all wool with the softest, finest fibers making the best performing fabrics (as seen in this classic cold weather merino long-sleeve from Icebreaker. It is also extremely moisture wicking and naturally antibacterial, meaning it won’t smell even after long hours of sweating. On the other hand, it takes a long time to dry and it is not as durable as some synthetic or hybrid materials.

Because of wool’s thermal properties, most winter base layers will be at least in part made of this natural fiber, usually enhanced with the addition of polyester (like in this lofted Patagonia base layer top). Hybrid materials dry faster than pure wool, are more stretchy and usually also cheaper; however, the more wool, the warmer the base layer. (When choosing a merino product, make sure to review the manufacturer’s policy on animal welfare.)

Synthetic base layers are a great choice for vegans or for high-intensity activities which don’t require as much thermal protection. The highly technical fabrics are designed to perform much better than their more commonplace counterparts. For example, this Columbia long sleeve with dots of real silver woven into the fabric is an expert at reflecting the body heat inwards. 

The right thickness 

Although it may seem like the warmest base layer out there is the right choice for winter, that isn’t always the case. In fact, many winter activities such as ski touring or ice climbing will leave you hot and sweaty. In these scenarios, moisture wicking is more important than thermal insulation, making a hybrid or synthetic base layer a good option.

As many manufacturers offer various thicknesses (or “weights”) of their base layers, choosing the right one also depends on the rest of your layering system. Primarily, the most thermal insulation comes from a lofty mid-layer, such as a sweater or a fleece. The warmer your mid layer, the less important it is that your base layer alone can keep you toasty. 

However, in cold conditions or for lower-intensity sports such as alpine skiing (just think of the time spent on the ski lift), a thick base layer is a must. Pure wool products are often rated from around 100 to over 300 indicating how many grams of yarn are used to make a square meter of fabric. Summer base layers are usually under the 150 mark, while extreme cold weather options start at 250 and above.

The right layering system

Base layer garments include a variety of tops as well as shorts and full-length tights. With fewer layers on your legs compared to the rest of the body, keeping them warm is often dependent on a base layer. Choosing the right fit will ensure that the garment does its job: for both upper and lower body, opt for a base layer that is as tight as possible, without restricting your movement so it can effectively wick moisture so sweat doesn’t drip down your back.

A base layer has to stay in direct contact with your skin—and that means all of your skin. In moderate conditions, it may not matter too much, but in extremely cold weather or for high-intensity activities, sweat-saturated boxer shorts or a wet bra can feel extremely unpleasant, compromise your performance or even your safety. Investing in woolen or technical synthetic thermal underwear will pay off in comfort, so if you don’t wear your base layer on bare skin, pair it with moisture wicking briefs and/or a bra top.

Once you’ve covered your basics, get to know more on how to create the perfect winter layering system by reading this post.