How To Choose A Base Layer

Hiking Base Layer

What’s Are The Most Important Things in a Base Layer?

Material – While all of the base layers we suggest are quick-drying, moisture-wicking, and breathable, each material has a specific advantage. Wool is excellent for controlling odors, breathing, and body temperature. Synthetics don’t get as warm, but they dry out quickly, are usually more affordable, and tend to be a little more long-lasting. Although silk base layers are incredibly comfortable, they will absorb more moisture than other materials and are best worn at night or when you won’t be perspiring much.

Weight – We prefer lightweight base layers for most 3-season excursions because they are more comfortable to wear underneath other clothing. For backpacking trips where you’ll be carrying your layers in your pack for the majority of the day and wearing them at camp at night, lightweight layers also help you pack lighter.

Warmth – What kind of weather you typically go out in is one of the most important things to take into account when selecting the proper base layers. To ensure that we are always dressed appropriately for any weather, we keep a choice from each of the warmth categories in our rotation of clothing.

Price – A great base layer doesn’t have to cost a fortune, but warmer layers and those made of natural fibers do tend to be more expensive. In an ideal world, you’d have several base layer tops to accommodate various weather conditions, so be sure to account for the combined cost when planning your budget.

What to expect from a base layer

Many hikers and mountaineers use a layered clothing system because it allows you to add or remove layers depending on the weather (changes in temperature, precipitation, wind and your activity level). Given that it comes into direct contact with the skin, the base layer is likely the most crucial component of the layered clothing system. Even with the best middle and outer layers, you won’t feel comfortable if your base layer isn’t performing well. Here is a thorough breakdown of base layer components.

A base layer is responsible for:

  1. Managing moisture

Since water has a thermal conductivity that is roughly 25 times greater than that of air, losing heat when wet is much more rapid than when dry. Additionally, wet clothing has a higher coefficient of friction, which can lead to itching and other discomforts. Because of this, in order to keep your skin dry, moisture—whether it comes from your body (perspiration) or the outside (precipitation)—must be wicked to the outside of the garment where it can evaporate or pass to the next layer.

  1. Protecting the skin

If you are only wearing a base layer (in warm weather), it should offer UV protection from the sun, protection from potential chafing from a backpack, and protection from vegetation.

  1. Maintaining the body’s natural temperature

The base layer must slow down the rate at which you lose body heat in cold weather. You will experience thermal discomfort as soon as the body’s thermal balance is disturbed; you may start to perspire in warm weather or become numb in a cold climate. Unfortunately, it is impossible to create a base layer that performs superbly in both extremely cold and extremely warm conditions because this requires different material thickness. High-quality base layers, however, can be worn in a variety of environments.

Base Layers – What characteristics to look for?


As previously mentioned, wet skin or a high moisture content between the skin and the base layer garment results in high thermal conductivity, which speeds up the body’s temperature adjustment to the outside environment. A base layer must wick moisture to the fabric’s exterior so that it can spread out flat and more easily evaporate, keeping your skin dry in the process. The hydrophobicity of the fibers (how much water do they absorb) as well as the thickness and porosity of the fabric have a significant impact on a fabric’s ability to wick moisture away from the body. The ability to wick away moisture is worse when the fabric is thicker and more water-absorbing. In order to produce the best results, manufacturers frequently manipulate the fibers in fabrics.

Quick Drying

In both hiking and mountaineering, there are periods of high intensity activity (moving upward) and then periods of low intensity activity (moving downward) or rest. Sweating increases during high-intensity exercise, which can cause the base layer to become saturated with sweat. When at rest or engaging in low-intensity activity in cold weather, the base layer’s increased thermal conductivity will cause rapid cooling unless it dries quickly or is made of a material that retains body heat even when wet (for example Merino wool and silk). A garment’s drying time is significantly influenced by the fabric’s thickness and water absorption properties. For instance, merino wool, which absorbs about 30% of its own weight in moisture, doesn’t feel clammy against the skin because the outer, hydrophobic portion of each fiber is in direct contact with the skin and doesn’t allow water to pass through it (water repellant). As a result, Merino wool retains heat better than other materials like polyester, despite the fact that the natural fiber takes longer to dry due to the limited increase in thermal conductivity.

Feeling against the skin

Base layers should be made of a material that is comfortable to the touch because they are worn directly on your bare skin. It all comes down to preference when deciding on the most pleasant/comfortable material for a base layer, similar to how some people prefer crisp cotton bed linen while others prefer silky satin.


Odor-resistant base layers are useful on longer hikes because they can be worn for days without washing, allowing you to bring along fewer items of clothing overall and lessen your load. Merino wool and silk are two materials that naturally resist odors; other materials, like polyester, can be treated to do the same. For synthetic fabrics, treatments with triclosan and triclocarban as well as silver-based compounds are the most widely used anti-odor textile treatments. All of these ingredients keep your clothes smelling fresh even after multiple uses because they are toxic to the bacteria that cause odors. However, over time these ingredients are washed out, which reduces the garment’s ability to resist odor. Depending on the overall quality of the garment, some reports claim that up to 45% of anti-odor compounds based on silver can be flushed away in just one wash.

Most Common Materials in Base Layers

The most typical materials used in base layers for outdoor activities like hiking and mountaineering are: Polyester, Merino Wool, Nylon, Cotton and Silk.

The characteristics of the most popular materials used in base layer clothing are listed below. Please be aware that these properties are also greatly influenced by the fabric’s thickness and porosity; for instance, a very thick and dense fabric will dry much more slowly than a thinner and more porous one of the same material.

 PolyesterMerino WoolNylonCottonSilk
Performance in absorbing waterExcellentDecentExcellentPoorDecent
Drying timeExcellentReasonableExcellentPoorExcellent
Warmth when wetPoorExcellentPoorPoorGood
Performance in wicking moistureExcellentGoodExcellentPoorGood

More about Base Layer Materials


Polyester is the most popular fiber for base-layer clothing because it is reasonably priced, offers great performance in some areas, and can be knitted into incredibly thin, yet sturdy, fabrics. Polyester is very common for Mid-Layers and Pants as well. Because polyester absorbs only 0.4% of its own weight in water, it dries quickly and effectively wicks moisture from the skin. Polyester fibers are frequently modified by manufacturers to improve performance. Arcteryx Phase and Polartec Power Dry are two examples of well-known polyester base layer fabrics made by changing the fibers. Both fabrics have a bi-component construction that combines two distinct types of yarns: an inner yarn that absorbs moisture from the skin and an outer hydrophilic (water-absorbing) yarn that disperses the moisture on the surface for quick evaporation. These sophisticated fabrics keep you dry because the inner yarn absorbs very little water, effectively preventing conductive heat loss. These fabrics are more expensive than base layers made of other types of polyester, though.

For hikes lasting up to a day in warm weather, we advise wearing polyester base layers. Polyester’s poor odor resistance makes it problematic on longer trips, necessitating the need for you to pack more base layer clothing. Merino wool performs better in colder climates because it retains warmth even when wet, reducing conductive heat loss.

Merino Wool

Because it is naturally antimicrobial and provides excellent temperature regulation, merino wool is growing in popularity among hikers. It’s commonly used in Base Layers, Mid- Layers and Socks. Many people still believe that wool is only appropriate for cold climates, but Merino wool actually helps to keep your body temperature around 37C, so it keeps you comfortable in both hot and cold climates. Merino wool fibers are smaller than 24 microns in diameter, setting them apart from regular wool. The softness of the wool increases with decreasing diameter. Merino wool comes in six different grades, including:

  • 17.5 microns – Ultrafine Merino Wool
  • 18.5 microns – Superfine Merino Wool
  • 19.5 microns – Extra Fine Merino Wool
  • 22.5 microns – Medium Merino Wool
  • 24 microns – Strong Merino Wool

Since wool fibers with a larger diameter tend to be too rough to be worn directly against the skin, base layer clothing made of graded ultrafine, superfine, and extra fine Merino wool is ideal. The density of base layers made of Merino wool varies. Typically, the density ranges from 135g/m2 to 400g/m2. While wool base layers are primarily made for use in the winter, spring, and fall, those with a density of 170g/m2 or less are suitable for use in hot climates. Merino wool base layers (and mid-layers) with a density above 250g/m2 have a tendency to be too heavy (especially when drenched in perspiration) to be effectively used for sports. They also perform poorly in terms of drying.

The main benefit of Merino wool over polyester is that it keeps its warmth even when wet. This is possible because only the fiber’s interior, which is closest to your skin, absorbs water; the exterior, which is not in contact with your skin, remains dry. As a result, base layers made of Merino wool effectively stop conductive heat loss. They also provide significantly better (and long-lasting) odor resistance than polyester. Merino wool takes longer to dry and is lighter than polyester. Ibex, Icebreaker, SmartWool, and Woolx are well-known companies that sell products made of merino wool.

Because of the extraordinary capacity to stop conduction heat loss, merino wool base layers are advised for hiking excursions in moderate to cold weather. No matter the weather, we also advise wearing base layers made of Merino wool for extended hikes where odor-resistant clothing is essential. A lightweight polyester base layer might be preferable for quick hikes in hot weather.


Nylon is rarely used for base layers due to its poor breathability. Nylon is more common when it comes to Backpacks, Pants and Outer-Layers. Besides the breathability point, Nylon performs similarly to polyester in terms of moisture wicking, quick drying, and water absorption. When compared to other base layer fabrics, nylon’s durability is its main advantage. Since nylon is so strong and resilient, it is ideal for clothing that is frequently subjected to abrasion. Manufacturers typically include ventilation panels in the key locations of nylon base layers. These ventilation panels increase the overall breathability of the garment because they are constructed from thinner, more breathable fabrics, like polyester. Since nylon is not stretchy, it is frequently combined with Spandex or other fabrics that are.

Nylon base layers are advised for hiking in warm weather (when worn alone) if the terrain necessitates wearing tough, abrasion-resistant clothing (hiking through woods, shrubbery etc).


Since cotton performs poorly at controlling body temperature, it is rarely used as a base layer material for hiking. Since cotton is so water-absorbent (it can hold up to 2500% of its own weight in water), hikers who wear cotton as a base layer frequently experience rapid conduction of heat loss in cold weather. Cotton also has a reputation for being difficult to dry and having subpar moisture-wicking capabilities (it rather absorbs the moisture than transfers it away from the skin). However, some producers make base layers for hiking out of cotton and polyester blends. Cotton is used in this situation because it is breathable and has a pleasant texture that is incredibly soft to the touch. Cotton has better odor resistance than polyester as well. The drirelease fabric, which is cozy and offers good performance, is an example of a good blend of cotton (15%) and polyester (85%). Numerous base layers made by the renowned company ExOfficio contain this fabric.

Pure cotton base layers are not advised for use while hiking. If you prefer cotton’s softness, base layers made of cotton and polyester blends, which offer the best qualities of both fabrics, are advised. Cotton’s poor ability to regulate temperature, however, should be avoided in cold climates.


Silk base layers are rarely worn by hikers because the material hasn’t yet become widely accepted. However, silk performs exceptionally well because it is remarkably lightweight and warm. Silk absorbs up to 30% of its own weight in moisture, similar to Merino wool, but because the moisture is trapped inside the structure of the fiber, it doesn’t feel clammy against the skin. Additionally, silk dries quickly and has excellent moisture-wicking properties. It has a pleasant feel against the skin and is naturally antimicrobial. The cost of silk is the only drawback.

For those who are not afraid to try new things, we advise silk base layers. Silk base layers are appropriate in all environments.

How thick/heavy should my base layers be?

Base layers are typically broken down into four thickness categories:


If there wasn’t an ultralight category, it wouldn’t be backpacking, right? For warm to moderately cool weather, ultralight base layers work best because they quickly wick away sweat and moisture while still offering some warmth and protection.


Lightweight base layers are slightly thicker but still offer excellent moisture wicking and warmth for cool to moderately cold temperatures. These base layers are also the most appropriate for high-intensity activities, though you might want to wear them with an additional midlayer if temperatures are predicted to drop.


Midweight base layers will provide warmth and light wind protection once the temperatures start to fall. They still have good wicking properties, but because of their thicker insulation, you will probably start perspiring quickly if you engage in any activity that is more strenuous than moderate.


These base layers are the thickest and are designed to trap and maintain heat. The amount of material in these layers makes it more difficult for water to permeate them quickly, even though they still wick moisture away more efficiently than, say, blue jeans or a down jacket. Heavyweight base layers should therefore generally be saved for leisurely or low-intensity activities. These should be your go-to layers for camp if you will be in extremely cold weather, strong winds, or both.

Midweight and heavyweight base layers are best suited for low-intensity activities and/or cold temperatures.

As stated in the descriptions above, be sure the base layer weight you select is suitable for the upcoming activity and the weather. Many hikers don a midweight base layer before starting out on the trail, only to change out of their perspiration-soaked pullover a mile later. A good rule of thumb is that you are probably wearing the right base layer if you are still at ease after fifteen minutes of hiking.

Should I carry extra base layers?

While some ultralight hikers may disagree, it’s always a good idea to pack an extra set of base layers because it allows you to separate one set for the trail and another set for camp.

Even though many base layers have antimicrobial and/or odor-resistant properties, it’s still a good idea to keep a fresh, dry set of base layers in your camping gear.

The trail’s conditions should be taken into consideration when selecting your base layers. These layers should be more resilient and thinner to handle intense physical activity. Additionally, they will accumulate all of the sweat and dirt from your hiking excursions, resulting in a buildup of stench that will last until your next trip to the laundromat. After a long, sweaty day of mountain climbing, there isn’t much that is more uplifting than changing into a clean set of base layers.

The ability to quickly change out of wet clothes when your activity level declines and the temperature drops, however, is extremely important. Even quick-drying base layers will hold onto moisture for a while. It doesn’t have to be rainy to end up drenched by the end of the day. A sweat-soaked shirt can be just as dangerous in freezing temperatures, as moisture can quickly cool to levels that will, at best, make you uncomfortable, and at worst, result in hypothermia.

As a result, it’s usually a good idea to save your thicker base layers for camp. Maintaining them in a waterproof bag will ensure their usefulness. 

Underwear Fit

Your next-to-skin layer must be directly on your skin in order to effectively wick sweat. Therefore, your objective should be to fit snugly everywhere. But don’t just rely on marketing jargon like “athletic fit”; try it on first to be sure.

In a base layer for warm weather, some individuals prefer a loose fit. They reason that doing this will result in better cooling and air circulation. However, a loose fit reduces the effectiveness of wicking. Additionally, some base layers for warm weather disperse sweat over a sizable surface area, which, when evaporation occurs, cools a sizable area.

Caring For Technical Fabrics

To maintain their peak performance, technical fabrics need a little extra maintenance. Always carefully follow the washing instructions on the tags, but in general, remember the following:

  • Use a front-loading washing machine – A top loading washer’s agitator can damage seams and snag drawstrings or zippers. Before washing, make sure to close all the zippers and tie the drawstrings to prevent tearing.
  • Make use of a technical fabric wash – For washing any technical fabrics, we advise using Woolite or Nikwax Tech Wash as these products won’t leave scents or residue on your clothes.
  • Only wash when absolutely necessary – Many technical fabrics have antimicrobial properties and aren’t meant to retain odors. After each use, hiking clothing doesn’t necessarily need to be washed.
  • Avoid using dryer sheets or fabric softener – Dryer sheets and fabric softener can leave residue on the fabric and have a negative impact on its performance.
  • Hang dry whenever you can – It is best to lay technical fabrics flat or hang them on a line to dry naturally because heat and agitation in the dryer can harm them.