How to choose a base layer


Base layers are essential for keeping warm during the colder months. But what are they and why do you need them?

What is a thermal base layer?

A thermal base layer is a thin layer of clothing that insulates your body in cold and freezing conditions. It’s usually worn underneath other items of clothing as the layer that sits closest to your body, allowing air to be trapped between the clothing and your skin. This helps to maintain body heat, while wicking and evaporating your sweat to ensure you stay warm, dry and comfortable.

Base layers are an essential piece of kit on winter trail runs, when mountaineering or hitting the ski slopes. Deciding what base layer to get can be a tricky business, though, with so many different options on the market. We’ll take a look at the different options available to help you decide what the right one is for your activity.

When to wear a base layer

Although you might typically think of base layers as being for winter, they can actually be beneficial all year round. A layer of sweat-wicking fabric next to your skin can help to keep you cool and dry when it’s warm outside and many athletes - cyclists in particular - choose to wear a base layer in the summer months.


They really come into their own in winter, though, helping your body to maintain heat when the temperature drops. Whether summer or winter, layering your clothes is crucial. You can remove layers if you get too warm, and add layers if you get cold.

Base layers can be worn for any sort of activity, including skiing and snowboarding, cycling, running, hiking and mountaineering.


Base layer fabrics

When it comes to thermal base layers, there are three different kinds of fabrics; each has its advantages. Let’s take a look at the main materials used.


Merino wool


Merino is a soft, fine knit that can be used alone or blended with other fabrics to make it stretchier and more durable. Unlike traditional wool which, when wet, retains water and becomes really heavy, merino wool wicks moisture away, an essential feature for any piece of clothing that you’re going to be getting hot and sweaty in.

Another great benefit of merino is that it’s naturally odour-free. Even if you wear the same top for days on end during a big hiking expedition, it won’t retain odours like synthetic sportswear can. 

It’s also the warmest type of fabrics, making it a good choice for activities like skiing and snowboarding where you’ll be outdoors in cold temperatures for a long period.


Synthetic fabrics


When it comes to synthetic base layers, it’ll usually be polyester or a mixture of polyester and other fabrics. Although merino is fairly efficient at wicking away sweat and moisture, synthetic fabrics are even better and dry extremely fast. 

This type of base layer tends to be more durable than merino as well - perfect for climbing and mountaineering where constant movement means more friction. The downside of synthetic base layers, though, is that they’re not as odour-resistant as merino, so if you’re looking to wear them multiple times between washes, you may have to build up a bit of a stink tolerance. 




Silk is super soft and feels comfortable against your skin. However, unlike either synthetics or merino, it doesn’t wick moisture well, and it’s not particularly odour-resistant. Silk is best kept for low-impact activities like yoga where your heart rate is kept relatively low and you’re not working up much of a sweat.


What’s the importance of sweat-wicking fibres?


One of the key things we’ve mentioned for each of these types of base layers is how effective they are at wicking sweat away. But what does that really mean, and why is it so important for a base layer?

If a fabric is moisture-wicking, it means that it moves moisture away from your skin from the inside of the material to the surface, by drawing it through narrow spaces in the fabric. This is important when you’re doing any sort of physical activity as it ensures sweat is quickly moved to the top layer of fabric, drying quickly so it doesn’t soak through the clothes. This is particularly important during the winter months when you need to stay dry to stay warm. If a fabric is left wet against your skin, you’ll quickly start to cool down, which could eventually lead to hypothermia.

That’s why it’s so important to look for a fabric that’s sweat-wicking when choosing a base layer. You need to stay warm and dry so you can focus on the task at hand, whether that’s careening downhill on skis, or heading up the mountain on foot.

What type of base layer should you go for?

Through research and development, The North Face®’s choice in thermal base layers are made of materials such as synthetic fabric that is a blend of polyester, spandex, nylon, and lycra that provides just the right amount of warmth with heat retention and moisture-wicking properties.


What are the different types of base layers?

From short-sleeved vests to long-sleeved tops and from shorts style to long leggings, there are multiple different types of base layers, all of which have their own benefits.


What is a base layer top?

A base layer top is ideal for maintaining body temperature, helping wick away moisture caused by sweat from the skin, so you stay warm and dry in all weather. Base layer tops are mostly worn in the winter for keeping warm and in the summer for staying cool and dry.

Summer base layer tops are often in the style of vests and t-shirts, although you also get long-sleeved summer tops that are thinner than their winter counterparts.

Winter base layers tend to be long-sleeved and thicker fabric than summer versions - but of course, the style you choose comes down to your own preferences. What will you be wearing with your base layer top, and what activity will you be doing.


How to wear your base layer top


Base layer tops are particularly popular with sports enthusiasts, especially skiers, hikers, climbers and snowboarders You can wear a base layer top and stay warm or cool and dry without the heat or the cold affecting your performance. Something like the Women’s Dotknit Baselayer is perfect for layering under your outerwear to keep you warm. Designed for skiing and snowboarding, it’ll also work well for any other activities where you’ll be spending prolonged periods in cold weather.


What are base layer pants?

Base layer pants are thin, comfortable leggings worn by both men and women. They usually come in a long-length leggings style, but you can also get shorter pairs. They are designed to manage moisture effectively while adding a layer of warmth under trousers. 


How to wear your base layer trousers


Bottom base layer pants like the Men’s Active Tights should feel snug but not too tight. Just like top base layers, a snugger fit will offer more warmth. They should reach the bottom of your lower leg and rest around the ankle area unless they are a three-quarter length. Going with the same size as your standard size will be adequate when sizing baselayer bottoms. 


What are compression base layers?

Compression base layers are designed to be tighter fitting than ordinary base layers, and they provide more than just warmth. Compression clothing is designed to support fatigued muscles by promoting blood flow and oxygenation to your muscle tissues.

Base layers made with compression in mind often feature compression panels throughout the garment. These panels are usually found furthest away from your heart, for instance around the ankles in a pair of leggings. This is because the panels squeeze your muscles, helping to push blood back up your legs and towards your heart.

Compression can also help your muscles to recover after a big session and can help reduce your experience of delayed onset muscle soreness (DOMS).


How to wear your compression base layer


Compression wear is perfect for sports, such as trail running, and is often worn on its own in the warmer months rather than as a base layer for winter sports.

A compression layer like the Men’s Pro Tights can be worn alone, layered with a pair of shorts, or under another pair of trousers with the compressive fit keeping your muscles active at all times. Not just to be worn for running, hiking or snowboarding, compression tights can also help your muscles to recover in the hours and days after a training session. 


What to look for in a base layer

When shopping for base layers, there are a few different things you should look out for to ensure you choose the perfect layer for your activity.


Check the fit


Base layers should be snug fitting but not so restrictive that you can’t move when exercising. Warm air needs to be trapped between fabric layers without the possibility of feeling a draft if you are to stay warm. 

Don’t be fooled into thinking the tighter it is, the better it will perform. It must fit your body properly; compression that is too tight can prevent circulation. It’s generally best to go for your regular size when buying a base layer, as they’re deliberately designed to be slightly smaller for a closer fit.


Dress for comfort


Thermal base layers should be made of fabric that is stretchy, moisture-wicking, quick-drying, and, of course, they should be warm. They should be soft and comfortable to wear as they are going to be your first layer of clothing next to the skin. A good thermal base layer should provide all-around comfort and protection during colder months.


Are base layers breathable?


For intensive exercise, look out for base layers that are breathable and offer ventilation. One great way of getting more airflow to your body is with a neck zip, as in the Men’s Sport Long Sleeve Zip Top. You can also look for perforated material in key areas of the garment, particularly under your arms and on your back.


Will there be any friction?


Base layers sit right beside your skin so you want to ensure that there’s no rubbing, which could cause uncomfortable chafing. Look for flat-lock seams or seamless garments to avoid friction under your arms. If you’ll be wearing a rucksack, you might want to check whether there are any seams on the shoulders too.


How thick should it be?


It’s down to personal preference and chosen activity whether you go for lightweight, midweight or heavyweight base layers. The colder the temperature, in general, the warmer you’ll want your base layer to be - but it also depends on your normal body temperature and the level of activity you’ll be doing. For moderately cool temperatures, you can generally get away with a lightweight layer. If it’s cold, then choose midweight, and if it’s below freezing, heavyweight is the one to go for.

Remember, though, that the key to staying warm outside - no matter what activity you’re doing - is layering. Now you’ve got your base layers sorted, check out our guide to layering to keep you warm all winter long.