When you’re out on a long hike, run, or any adventure, your base layer of clothing can make or break your experience. Even if you’re wearing high-quality mid and top layers, a poorly-performing base layer can lead to a miserable time. There are lots of things to consider when choosing your base layer of clothing, and one of the most important is the material (or materials) from which it is made.
In this guide, we’re going to touch briefly on what the base layer is and its important functions. Then, we’re going to go over each type of material that base layers are commonly made from and share the advantages and disadvantages of each. By the end of this guide, you’ll know exactly what base layer materials you want to wear and when you want to wear them!
What Is The Base Layer?
The base layer consists of the clothes that you wear closest to your skin. Technically, this does include your everyday underwear. Consider this carefully when you’re picking out your undies for a hike– you don’t want to wear something uncomfortable and end up chafing in your most sensitive areas!
Any type of clothing can be part of your base layer, and your base layer will change throughout the seasons. The warm, comfy thermals you wear in winter will not be part of your summer wardrobe, after all!
What Does The Base Layer Do?
The base layer of clothing is one of the most important layers for thermoregulation or control of your body temperature. You can always remove or add mid and top layers, but your base layer stays on. There are three major functions of the base layer: managing moisture, protecting the skin, and maintaining your body’s correct temperature.
If you exert effort, you’re going to sweat. There’s no way around it, and there shouldn’t be a way around it because sweating is how the body maintains its temperature. When you sweat, your body’s temperature is brought down through the evaporative cooling process.
But that process evolved millions of years ago. Today, sweating is still important– but today we also wear clothes that can trap that moisture next to our bodies, and that’s a problem. Water is much better at conducting heat than air is. Water transfers heat almost 25 times faster than water does, which means that you lose heat much faster when you’re wet. If your sweat is trapped by your clothes and has nowhere to go, you can actually get too cold. Hypothermia is a serious threat, and more people actually die from it in summer than in winter because they’re not expecting it.
In addition to the serious threat of hypothermia, wet clothing also is more likely to cause chafing and discomfort. This is why you need a base layer that can properly manage moisture. This property is called moisture-wicking, and it relies on the principle of capillary action to move water away from your skin and to the outside of your clothing, where it can easily evaporate.
During hotter months, it’s likely that you’ll only be wearing one layer of clothing. If that’s the case, it needs to be protective! There are quite a few potential hazards a warm-weather base layer should protect you from. The first is the sun– you can actually get clothing with built-in UV protection. Chafing is another concern, as are trail hazards like vegetation.Your base layer should have sun protection capabilities if it may also be your outer layer, but even with UV protection, you need to make sure you have sunscreen to apply to non covered areas.
Even in hot weather, your base layer needs to help manage your temperature. If your base layer is too insulating, you’ll overheat. In cold weather, though, the base layer needs to reduce the rate of body heat loss. Each season requires a different performance out of your base layer, and that means that you need to have appropriate base layers for all the conditions you may be in. High-quality base layers can handle a wider range of conditions, but even the best base layer may not be perfect in both winter and summer.
Do I Always Need A Base Layer?
Yes, unless you like to hike in the buff… which for many reasons, we absolutely do not recommend! Even though you might not think of a t-shirt and hiking shorts as a base layer, if that’s all you’re wearing on a summer hike… that is your base layer! Base layers aren’t just long johns or thermal gear– it’s any clothing that’s worn directly next to your skin.
Base Layer Materials
There are many materials that your base layer clothing can be made from. These include both natural and synthetic fibers, as well as combinations of different fibers.
Bamboo is a natural fiber that’s been gaining popularity in recent years. Fabric made from bamboo cellulose is prepared in a way similar to rayon, a synthetic fiber that was originally designed to mimic the properties of silk. Bamboo fabric is moisture-wicking and thin enough to dry quickly. It is very breathable and is naturally antibacterial and antifungal, which means that it’s highly odor resistant.
Pros of Bamboo
- Moisture-wicking properties
- Natural UV protection – cuts out up to 98% of harmful UV rays
Cons of Bamboo
- Less readily available
- Can be expensive
- Thicker bamboo fabric does not dry quickly
When you’re looking at base layers, you almost never want 100% cotton. The reason for this is cotton’s water absorption abilities. Cotton is a natural plant fiber that’s composed almost entirely of cellulose, which can absorb up to 2500 times its weight in water. If you’re doing anything strenuous in cotton clothing, it will absorb all of your sweat and just hold it there. Cotton on its own isn’t really that good at wicking away moisture, and while it dries quickly, it doesn’t usually dry quickly enough. There’s a saying among hikers: “Cotton kills.” It’s not without reason. But! That doesn’t mean that all cotton clothing is bad or dangerous! Cotton is a great mid-layer, but more frequently, you’ll find cotton blends for activewear. Cotton blends are awesome because they combine cotton’s lightweight and breathability with other fibers’ moisture-wicking capabilities.
Pros of Cotton
- Blends well with other fibers
- Can be eco-friendly
- Naturally odor resistant
Cons of Cotton
- Absorbs and holds onto moisture
- Doesn’t wick away moisture
Another natural fiber, hemp is a versatile fiber that has a lot of fans in the environmentalist community, since it’s a natural carbon sink. Unlike cotton, hemp is naturally moisture-wicking. It’s also even more lightweight than cotton, so it’s great for summer base layers. Hemp fabric also provides natural protection against UV rays, like bamboo, and is extremely breathable.
However, hemp has its downsides, too. It’s not particularly good at insulating, nor is it entirely water-resistant. If you completely soak hemp, it will take longer to dry than a fiber like cotton. It’s also quite expensive and has a rougher texture than other types of plant fibers. As such, it’s frequently seen in blends.
Pros of Hemp
- Naturally odor-resistant
- Naturally UV protective
Cons of Hemp
- Not very comfortable on its own
- Does not insulate when wet
Merino wool is a special kind of wool that is becoming increasingly popular for outdoor gear. Merino wool offers amazing temperature regulation and is naturally antimicrobial, meaning it’s highly odor resistant. Merino wool isn’t just for cold weather– it helps regulate your body temperature even in warm months. The fibers are extremely thin, less than 24 microns in diameter. For base layer clothing, you want Merino wool that is graded as Ultrafine, Superfine, or Extra Fine, as anything coarser isn’t comfortable to be worn directly against the skin.
The biggest advantage of Merino wool is that it maintains insulation while wet. Only the inner part of the wool fiber absorbs water, which is true of all wool– but Merino is finer, less itchy, and overall higher performing than the other types of wool. It isn’t as light as polyester or other synthetics, but for thermal regulation, it’s the best.
Pros of Merino Wool
- Naturally odor resistant
- Retains heat when wet
- Naturally moisture-wicking
Cons of Merino Wool
- Doesn’t dry quickly
- Not as readily available as synthetics
- Less durable than other fabrics
Nylon is a synthetic material that isn’t frequently used today by itself for base layer clothes. The reason for this is that nylon isn’t particularly breathable. You’re far more likely to see it as an outer layer because it’s tough and durable. For clothing that is exposed to abrasion, you can’t really outperform nylon. Nylon is also frequently woven into waterproof fabric, so you’ll frequently see it in rain jackets.
Aside from breathability, nylon is very similar to another common synthetic material, polyester. Both nylon and polyester are moisture-wicking, quick-drying, and absorb very little water. Typically when nylon is used for base layers, it will be blended with other fibers. You will also frequently see nylon blended with Spandex because nylon is not stretchy on its own. You will also see ventilation panels added by the manufacturer to nylon base garments.
Pros of Nylon
- Easy to find
- Dries quickly
Cons of Nylon
- Not breathable
- Insulates too well sometimes
- Not eco-friendly
Polyester is a very popular choice for base layer garments. It’s a relatively inexpensive synthetic fiber that can be woven into a variety of fabrics with different performance specifications. Polyester is not at all water absorbent; it only absorbs around 0.4% of its weight in water. This means that it dries quickly and can have great moisture-wicking properties.
Some polyester can even be woven to mimic the natural hydrophobic properties of wool. With this high-end polyester fabric, the inner core of the yarn absorbs moisture while the outer yarn spreads the moisture to the surface for quick evaporation. This keeps you nice and dry, although garments made of this material can be quite pricey.
Pros of Polyester
- Readily available
- Dries very fast
- Easy to wash
Cons of Polyester
- Not naturally odor-resistant
- Not eco-friendly
- Higher performance polyester is expensive
Silk is still relatively uncommon as a base layer on its own. You’re more likely to see it blended with Merino wool than to see it on its own– but silk is a great material for base layers, especially when you’re wanting to wear something light. Silk is incredibly lightweight. It’s a natural fiber– and technically, it’s an animal fiber, since it’s produced from the cocoons of silk moths. Similar to Merino, silk locks away water in the inner core of the fiber and doesn’t feel wet against the skin. It’s not as efficient at temperature control as Merino, but it is much lighter and faster drying.
Silk also feels great against the skin and makes any fiber it’s added to feel better as well. Silk rates high in comfort and is naturally antimicrobial, so it doesn’t smell and can be worn for a long time before getting gross enough that it needs a wash. And while you might think silk is too delicate to throw in the laundry, that’s not true anymore. Modern silk fabrics are easily cleaned at home. You do need to follow the instructions and use cold water only, but it’s not nearly as delicate as you might think.
Pros of Silk
- Dries quickly
- Naturally odor-resistant
- Wicks away water
- Keeps you cool in summer and warm in winter
Cons of Silk
- Trickier to wash than synthetic material
- Not as readily available
Wool is a natural fiber produced by sheep. (Goats produce wool, too, but the fiber industry is dominated by sheep.) Wool is infamous for being somewhat scratchy and hot, meaning you really don’t want to wear it in the summer. Merino wool is another story– that fiber is lightweight enough to be comfortable in the summer. But regular wool is too coarse and too warm for summer wear.
Wool’s weight and interlocking fibers, however, mean that it’s a great material to wear in winter when you want to stay warm. Wool also is somewhat water-resistant naturally, thanks to the lanolin that coats the fibers. Lanolin is a natural oil produced by sheep, and it helps keep you warm and dry in a wool garment.
Wool also has another major downside, and that’s durability. Wool fibers can felt together with compression or abrasion over time, which you don’t want. This happens because the surface of a wool fiber is actually coated with tiny scales that interlock with the scales on other wool fibers. This helps create wool’s natural water-wicking ability, but it also means that you have to be really careful when you wash 100% wool clothing. You will need to use a special detergent for wool, like Woolite, and you might not be able to put wool clothing in the dryer. Pay attention to the washing instructions so you don’t wreck your wool!
Pros of Wool
- Naturally water-resistant
- Naturally odor-resistant
Cons of Wool
- Sometimes it’s too warm
- More complicated to wash than other fabrics
The Best of Both Worlds: Blended Materials
Blended materials make amazing base layers because they combine the best traits of different fiber types to make high-performance materials that stand up to any conditions. There are dozens of different blended materials out there, each with its own unique traits.
Some common blends you might see include:
- Cotton and Polyester– blending these two combines cotton’s lightweight and comfort with polyester’s water-wicking abilities
- Hemp and Cotton– this blend improves cotton’s ability to wick away moisture and protect against UV rays while still retaining the comfort of cotton
- Merino and Cotton– this blend lightens Merino and makes it more breathable and comfortable
- Merino and Polyester– this blend is stronger than Merino alone but retains its unique characteristic of retaining heat while wet
- Merino and Silk– improves Merino wool’s strength, washability, and comfort
- Nylon and Spandex– this blend combines nylon’s extreme durability and Spandex’s stretch
- Wool and Polyester– this blend makes more wool comfortable and durable while still retaining its ability to insulate and retain heat while wet
Base Layer Characteristics
With all of that information about base layer materials, you should be able to make an easier choice about what kind of base layer clothing to buy. But there are other characteristics that inform this decision, too!
Never buy a base layer garment that doesn’t have some kind of moisture-wicking properties. A fabric’s ability to wick moisture away depends on how much water the fibers absorb, the thickness and porosity of the fabric, and any post-manufacturing treatment (like you’ll often see on high-quality synthetics). The more water-absorbing the fabric, the worse it is at wicking away moisture. Even when you’re buying winter gear, you should choose a thinner garment with better moisture-wicking abilities. You can always add more layers if you’re cold, but if you’re wet from sweat that hasn’t been wicked away, you’re in danger.
Any intense activity that leads to sweating, even in winter. If your base layer isn’t quick-drying, you will find that your temperature drops too quickly because the fabric stays wet if you sweat. There are two good ways this can go to keep you safe and dry. The first is a quick-drying fabric. The second is a fabric that insulates when wet, like wool or silk.
Fabric drying times are greatly impacted by the thickness of the fabric and how much water the fibers absorb. Some fabrics, like wool, are highly absorbent, but wool is a special case. Wool absorbs moisture in the inner part of the fiber, but not the outer part that touches your skin. This is one of the big advantages of wool and Merino wool.
It doesn’t matter if a garment is made of the most high-tech material in the world– if it’s not comfortable, you’re not going to wear it! Don’t pick a base layer that feels bad against your skin.
Another element of comfort is how the base layer smells. Natural fibers are naturally odor-resistant, but many synthetics have anti-odor treatments. A high-quality odor-resistant base layer can be worn for days without needing to be washed, which is important for longer hiking trips where you want to keep weight to a minimum.
Base Layer Recommendations By Season
So with all this in mind, here’s our advice on choosing base layers according to typical seasonal weather patterns.
In cool, breezy Spring months, you want to wear base layers that aren’t too heavy and wick away water. High-performance polyester, Merino wool, hemp, and hemp blends, and Merino blends are all great options for this kind of weather.
On rainy days in Spring, the temperature can drop quickly. Merino and Merino blends, as well as good polyester, are excellent choices for rainy spring hikes.
During the heat of Summer, something cool and lightweight is a great option. Polyester, Merino and Merino blends, cotton/hemp blends, bamboo, and silk and silk blends are all lightweight and breathable. These choices will also wick away water and sweat and will dry quickly if they get drenched. Bamboo, silk, and hemp also get bonus marks for their natural UV protection. You can also find polyester that offers UV protection, too.
Fall temperatures can be unexpectedly cold, especially if you’re hiking at high elevations. As always, a high-performance polyester is a good option, as are Merino wool and wool blends. By the time Fall rolls around, you probably don’t want a cotton blend, unless it’s a particularly warm day. The odds are good you’ll want something with better insulation than what even cotton blends can offer.
If you’re hiking in winter, you definitely want something warm and insulating next to your skin. Polyester, Merino wool, wool, and blends of those are all great choices to keep you warm and dry. Merino/silk blend socks are particularly good for winter since they can keep your feet toasty warm and not sweaty… and those fibers’ natural anti-bacterial properties mean that your socks won’t be stinky at the end of the hike.
Max DesMarais is the founder of hikingandfishing.com. He has a passion for the outdoors and making outdoor education and adventure more accessible. Max is a published author for various outdoor adventure, travel, and marketing websites. He is an experienced hiker, backpacker, fly fisherman, trail runner, and spends his free time in the outdoors. These adventures allow him to test gear, learn new skills, and experience new places so that he can educate others. Max grew up hiking all around New Hampshire and New England. He became obsessed with the New Hampshire mountains, and the NH 48, where he guided hikes and trail runs in the White Mountains. Since moving out west, Max has continued his frequent adventures in the mountains, always testing gear, learning skills, gaining experience, and building his endurance for outdoor sports. You can read more about his experience here: hikingandfishing/about