For a decade, our team of experts has bought and tested 43+ of the best base layers on the market. For this update, we compare 15 of the most popular options side-by-side. From the ski slopes to alpine climbs to sleeping out under the stars, our in-depth analysis derives from real-world adventures undertaken while wearing each model. We score all base layers across key areas of performance like warmth, breathability, and drying speed. Whether it's for the warm or cold season, a quality base layer is sure to keep you dry and comfortable, no matter where your next outdoor escapade takes you.Related: Best Base Layer for Women
Best Base Layer for Men
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|$59 List||$110.00 at Backcountry||$89 List|
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|Pros||Temperature regulation, ultra-cozy, balance of warmth and breathability||Spectra is the strongest fabric material on the market, lightweight, quick-drying, merino wool-like comfort||Uber soft Tasmanian Merino wool, efficient thermoregulation for weight||Efficiently wicks away moisture, comfortable fit, warmer than the weight suggests||Affordable, fashionable fit, breathable|
|Cons||Expensive, recommend special laundering, slow to air-dry||Easily picks up odor, stiff collar, lack of articulation||European cut is less accommodating, long dry times when soaked, bulky when packed||Heavy for its fabric weight, less abrasion resistant than other Merino-blended options||Finer thread Merino is not quite as warm, slightly itchy, shoulder top seams|
|Bottom Line||This all-around favorite continues to keep us warm, dry, and comfortable in nearly any situation||An ultralight, breathable base layer that incorporates Spectra fiber to make it the most durable on the market||Like the award-winning bottoms, this 100% Merino top is a near ideal midweight option, offering an impressive blend of warmth and breathability for winter athletics||A relaxed fit merino wool and recycled polyester blended top that offers an ideal combination of breathability and warmth to carry you through the shoulder seasons||This top delivers the fine qualities of a merino wool base layer without the extreme cost|
|Rating Categories||SmartWool Merino 25...||NW Alpine Spectra||Ortovox 185 Rock'N'...||Outdoor Research Al...||Meriwool Midweight...|
|Comfort And Fit (20%)|
|Drying Speed (10%)|
|Layering Ability (10%)|
|Specs||SmartWool Merino 25...||NW Alpine Spectra||Ortovox 185 Rock'N'...||Outdoor Research Al...||Meriwool Midweight...|
|Material||100% merino wool||90% polyester, and 10% Spectra||100% Tasmanian merino wool||47% merino wool, 47% recycled polyester (Repreve), 6% elastane jersey||100% merino wool|
|Fabric Weight||250 g/m²||105 g/m²||185 g/m²||150 g/m²||250g/m²|
|Weight (size M)||9.3 oz||4.8 oz||6.9 oz||7.6 oz||9.8 oz|
|Types available||Crew, 1/4 zip, hoody, onesie||Crew, short sleeve||Crew||Crew||Crew|
|Air Dry Test (minutes)||50||40||35||40||45|
|Fit||Slim fit||Slim fit||Slim fit||Semi-fitted||Slim fit|
|Stitching||Flatlock seams||Flatlock and flat seams||Flatlock and overlocked seams||Flatlock seams||Flatlock and flat seams|
|Shoulder top seams?||No||Yes||Yes||No||Yes|
|Drop tail hem?||No||No||No||No||Yes|
Best Overall Base Layer
SmartWool Merino 250 Crew
A top that is likely to earn its place as your go-to for all cold-weather activity, the SmartWool Merino 250 Crew continues to shine in this category. This remarkably versatile mid-layer offers superior comfort next-to-skin, and its 100% merino wool weave provides excellent temperature regulation, moisture-wicking capability, and all-natural antimicrobial qualities. We've worn it for days on end, both at home and out on multi-day backcountry trips. Unlike its synthetic competitors, it somehow manages to be very acceptable — stench-wise — after many days between washes. This layer performs well in a wide range of temperatures, allowing you to quickly transition from static cold to high-exertion, all while staying warm, dry, and comfortable.
As expected with natural fibers, this top will begin to slouch and sag a bit through consistent wear. The Merino 250 Crew (and all other merino tops we tested) requires special care when laundering to ensure the garment's longevity. When the fabric becomes completely saturated, this top is comparatively slow to dry. From the crag to the mountain and then back down for a night on the town, the SmartWool Merino 250 is comfortable and stylish enough to wear every day. It excels in practically any cool- or cold-weather activity, from resort skiing to winter alpine ascents to hanging on chilly mornings on desert climbing or rafting trips.
Read review: SmartWool Merino 250 Crew
Best Lightweight Base Layer
NW Alpine Spectra
Though the brand name and material may both be new to the scene, the two are working in conjunction to set a high bar when it comes to lightweight, technical clothing. The NW Alpine Spectra is just one piece in a line that is the first in the world to incorporate Spectra fiber — an innovative material that is engineered to be lighter and stronger than Kevlar. This highly technical, highly breathable, ultra-lightweight layer is able to easily withstand normal abrasion, rips, and tears, yet it is as soft next-to-skin as merino wool. No longer do mountain athletes have to sacrifice durability to save weight, nor do they have to substitute comfort for performance.
Though it is a versatile, lightweight option, the Spectra won't provide you with any of the insulation you may need to make it through the coldest days of winter. Despite all of the advances this top is making in the world of base layers, it still falls victim to some common pitfalls of full-synthetics — even casual efforts leave this top smelling as if you just pushed for an FKT. So while you may find yourself washing this top more than usual, you can rest assured knowing that the Spectra Long Sleeve won't wear out quickly. This ultra-durable lightweight base layer is built for the rigors of rock climbing but performs equally well as a trail running top or for working hard in the skin track when backcountry skiing. If you're looking for a lightweight base layer, this is the best we've tested.
Read review: NW Alpine Spectra
Best Midweight Bang for Your Buck
Meriwool Midweight Thermal
You may be surprised to discover that you actually don't have to pay an arm and a leg for a superb Merino wool top. The Meriwool Midweight Thermal offers near top-quality performance at a fraction of the cost of most of the 100% Merino tops we tested. Even though it is firmly in the midweight category, the extra-fine spun wool used to create this layer is more breathable than other directly comparable models, making it a great option for folks engaged in high-output activities like ski touring. Couple that with a slim, stylish fit, and you have a layer you can take from the mountain straight to après-ski.
With the benefits of increased breathability, you will sacrifice of a bit of warmth — don't expect this layer to be quite as warm as other 250 g/m² options included in this review. Though soft, the Merino wool is slightly itchy at first and takes some breaking in (read: responsible washing and drying) before it is snuggly-comfy. We hope that a future design of this shirt moves the seams off the shoulder top, which can rub when wearing a heavy pack. Beyond these small critiques, the Meriwool Midweight Thermal presents a reasonable entry-point into all-natural base layers. It is the perfect companion for cool-weather camping during the shoulder seasons, works well for both resort and backcountry skiing, and is certainly a stylish top to be worn casually.
Read review: Meriwool Midweight Thermal
Great Value for a Lightweight Top
Outdoor Research Echo L/S
If you're looking for a technical, lightweight base layer that won't break the bank, have a look at the Outdoor Research Echo L/S. This top is incredibly breathable and super lightweight, designed for sweat-inducing activities through the warmest months of the year. It's perfect for climbers, runners, or really anyone who spends much of their summertime out in the sun. The added UPF 15 treatment not only helps protect your skin but also increases the longevity of this already durable crew neck.
With a little extra fabric weight compared to others in its class, when properly layered, this top will continue to keep you dry and comfortable through the winter, only adding to its value and versatility. But don't get us wrong, this is not our go-to for warmth. While we wish that the ActiveFresh odor control did a better job of keeping us smelling fresh, the Echo's small pack size and quick dry time mean we're still going to bring it along on our next expedition trip, no matter the climate. If you plan to push hard uphill — whether it's running, ski touring, biking, or climbing — you will benefit from the performance of the Outdoor Research Echo L/S.
Read review: Outdoor Research Echo L/S
Best for Backcountry Skiing
Black Diamond Solution 150 Merino
The Black Diamond Solution is our recommendation for anyone who spends their winter days seeking out fresh tracks. This 150 g/m² option strikes a nice balance between mid- and lightweight, offering more versatility to wear as the season transitions from frigid winter temps to sunny spring riding. NuYarn is an innovative technology that specifically layers merino wool over synthetic fibers to best replicate the natural loft and breathability that makes the all-natural fiber so special. That means that even at a lower fabric weight, you are able to benefit from additional insulation created by an increased percentage of air pockets — without losing out on any of the breathability of this blended top.
This superior performance does come at a cost. Though the Solution may be the only base layer you need to get you through the winter, it's nearly twice the price of many other tops we tested. So it is particularly unfortunate that this prized piece is also susceptible to damage by abrasion. Fortunately, it is really intended to be worn at the base of a winter kit rather than as a standalone top for summer activities. Despite being pricey, its value will be apparent to guides and ski bums alike — particularly because you can actually get away with wearing this layer for multiple days, as our testers proved. While it excels as a backcountry skiing base layer, this is a great choice for any cold-weather alpine endeavor.
Read review: Black Diamond Solution 150 Merino
Why You Should Trust Us
Our expert for all things comfortable and cozy is Aaron Rice. Growing up on the Atlantic coastline and living up and down the Rocky Mountains for more than a decade, he knows all about making the most out of cold-weather playtime. A passion for winter weather led him to a bachelor's degree in snow and climate science. As a ski patroller and avalanche educator, you can often find him huddled in a snow pit, happily freezing his butt off to discuss the finer details of stellar dendrites. Outdoor educator and guide Roland Mott also adds experience and expertise to this review. Roland holds a degree in Outdoor Recreation Leadership and has guided rivers, backpacking, and climbing for 12 years throughout the US and Central America. He has also taught land stewardship and environmental ethics as a Master Educator for the Leave No Trace Center for Outdoor Ethics.
For our review, we identify six key metrics as essential to effectively grade a base layer top: Warmth, Breathability, Comfort/Fit, Drying Speed, Durability, and Layering Ability. Then we develop appropriate tests to carry out in the field and lab to test each metric individually. For metrics such as warmth, testing is as straightforward as wearing the garments in cold weather often and noting the relative differences. Other metrics, like durability, call for a combination of field use (i.e. chimney climbing and bushwhacking) and lab testing (repeated dry and wash cycles and an abrasion test.) From the high desert of the US Southwest to the craggy peaks of the Pacific Northwest, we wore these tops through a variety of activities — mountain biking, climbing, uphill and downhill skiing, trail running, backpacking, and more — testing and assessing their relative strengths and weaknesses along the way.
Related: How We Tested Base Layers
Analysis and Test Results
As a workhorse for thermoregulation, we understand the importance of having a base layer that will serve you well through all of your outdoor pursuits. That's why we start with only the best tops on the market and then proceed to field test the heck out of them. By submitting them to the wear-and-tear of everyday use and a variety of outdoor activities across a spectrum of temperatures and environments, we are best able to dial in which types of layers work best in what situations. We target the most important qualities to analyze and test these layers side-by-side according to these metrics. We offer this comprehensive review to help you land on the best base layer for your own needs.
Related: Buying Advice for Base Layers
It is important to note that the scores we assign are determined relative to the other products in the review. We purposefully choose to test the best layers on the market, so a low score in our testing does not mean a product is not worth its mettle. It simply means that it performed poorly in relation to the competition. We understand that the individual metrics that are important to some folks may not be as important to others. By testing and rating each of these layers relative to one another, we can highlight which score highest in the metrics that are significant for how you intend to use it.
The balance between price and value is a fine line to walk when researching a product. The argument of synthetic vs. all-natural fibers is a perpetual battle in the recreational apparel world, and we like to think of ourselves as conscientious objectors in this fight. But for the sake of producing quality reviews, alas, we must decide from time to time what materials are the best for certain situations. There are certainly pros and cons to each material type.
Synthetic fabrics tend to be less expensive, a touch more durable, and pack down smaller. They also tend to hold onto moisture, retain odors over time, and often don't provide the same warmth-to-weight when compared to their natural-fiber companions. Merino wool tops are typically more expensive and bulkier but offer benefits like superior body-temperature regulation, moisture-wicking ability, and odor resistance. Silk, while incredibly valuable in terms of warmth-to-weight-to-thickness, is a hard sell based on durability alone.
The Outdoor Research Echo L/S is one of the most valuable synthetic layers on the market today. This top is not only versatile as a standalone shirt for activities like running, but it performs impressively well as a technical base layer. If you're value-minded but tend to run colder, add a little warmth with an all-natural option like the Meriwool Thermal Midweight, a 100% merino wool layer that is very reasonably priced compared to its direct competition. It is a standout for 3-season recreation and works quite well as an athletic base for the coldest months.
One of the best ways we believe to determine value is to start with the following questions:
- How do I intend to use this particular layer?
- Do I want a layer that will keep me warm during the coldest months of winter?
- Or do I want a more versatile layer for the shoulder seasons?
These types of questions will help guide you in the direction of what holds more importance for you as a buyer. Decide which metrics are most important for your sport or activity — whether it's ice-climbing or shoveling snow in your driveway — and base your decisions on those factors first.
As the foundation of your layering system, warmth is one of the most important qualities to consider in your decision. It is not just about simple heat retention but rather the complex system of thermoregulation. A good base layer should trap heat to keep you warm in cold temperatures and also allow excess heat to escape when your heart rate climbs and body temperatures rise. It also involves wicking away sweat to keep you dry and protected from evaporative cooling. All of these ingredients are essential to a layer's ability to keep you warm and dry through a range of temperatures. An intensely warm top that doesn't breathe well may work for ice fishing, but it will likely leave you dangerously wet and cold during high-output activities like backcountry skiing.
We wore these layers through the varying temperatures of fall and winter to test every quality that results in you successfully staying warm and dry. We wore them as we skinned up windblown ridges in the Northwest, rowed through desolate canyons in the Southwest, slept on the frozen dirt after climbing sunny sandstone cracks, and explored trails by bike and foot in Colorado and New Mexico. The standout tops for well-balanced warmth are the SmartWool Merino 250, the Patagonia Capilene Air, and the Ortovox 185 Rock'N'Wool. These tops consist of thicker, cushy fabrics that seal in heat while maintaining excellent breathability and moisture-wicking abilities.
For those who work in extremely cold conditions — or who normally run on the chilly side — you may want to seek out those tops that favor pure warmth over breathability. The REI Silk Crew is an impressively warm, surprisingly thin layer that can supplement winter-wear without adding much bulk. For the deep cold of winter, we recommend the Smartwool Merino 250. As the heaviest 100% merino layer top we tested, this top is designed specifically with snow sports in mind. As an intriguing option to split the difference between light- and mid-weight, the Black Diamond Solution is as equally suited to working hard in the skin track as it is working all day in the snow. The Ortovox 185 Rock'N'Wool is similarly weighted to the Solution and is very similar in terms of offering a nice middle ground to split the seasons.
If you are looking for a layer that better suits highly aerobic activities or you want versatility across seasons, you will likely benefit from choosing a lighter-weight layer that is designed to breathe a bit better. Our testers' favorite aerobic layers are the Patagonia Capilene Cool Lightweight and Outdoor Research Echo L/S — these tops are perfect for 3-season activities like backpacking or trail running. For cross-country and backcountry skiing, we would opt for the lightweight layers that still offer a bit of warmth, like the NW Alpine Spectra, or the Outdoor Research Alpine Onset Merino Crew. If you're a rock-climber anticipating long-belay stances and short bursts of energy, check out the Patagonia Air Crew, Icebreaker 200, or SmartWool Merino 250, which all provide a solid level of warmth but still offer impressive breathability.
There are some specific features that we've found to help keep us warm and may help you narrow your search for the perfect base layer. Models like the Icebreaker 200 Oasis and the REI Lightweight Crew have a drop-tail hem. When skiing, we particularly appreciate the ability to keep your top tucked in and snow out of your pants. But these design features can also keep your top from rising up and exposing your back and belly when bending over to put on your climbing skins or reaching for that next crimper when climbing.
The Argument Against Cotton
There are significant differences between a natural fiber (Merino wool, silk) and a synthetic fabric (polyester, polypropylene) when it comes to warmth. The key here is that they both continue to insulate when wet. Comparatively, cotton can absorb up to 100% of its material weight in moisture, leaving you wet, cold, and miserable, and thus could be quite dangerous in certain situations in the backcountry.
Breathability is the yin to warmth's yang. Alongside warmth, it is arguably the most important quality of an effective base layer. Breathability is tied mainly to the moisture-wicking capability of a fabric. Effectively, this is the ability to collect moisture (sweat) and move that moisture to the outside surface of the fabric, where it can freely evaporate. The breathability of a garment is determined by how quickly and efficiently a fabric can convert sweat to free water vapor. A quality breathable layer will help regulate your body temperature through a range of environments, regardless of your energy output. Depending on the situation, a great base layer will effectively work to keep you dry and warm, or dry and cool, depending on how it's designed.
Breathability is an extremely important quality during active pursuits, as well as stop/start activities like backcountry skiing or rock climbing. A breathable shirt will allow the moist air hovering over your skin to escape through the material without saturating the fabric, thus keeping you warm and dry. A non-breathable shirt will prevent that moisture from escaping, leading it to condense on the inside of the garment. This leaves you wearing a sweat-saturated shirt that is wet, heavy, and potentially dangerous in cold conditions.
We assess each layer's breathability systematically to back up our findings after months of use hiking, running, skiing, climbing, and biking. We test each layer side-by-side in a temperature-controlled, indoor environment, and use the same short, rigorous exercise routine to work up a sweat. After stopping, we time how long it takes for our skin and the inside of our shirts to dry.
Not surprisingly, the tops that earn our highest scores for breathability are also made from the lightest weight fabrics. These are the Patagonia Capilene Cool Lightweight, NW Alpine Spectra, Helly Hansen Lifa Stripe, and both of Outdoor Research's options: the Alpine Onset and Echo L/S. As a bit of an outlier, the Patagonia Capilene Air continues to impress with its unique ability to masterfully balance warmth and breathability. We appreciate merino-blended options like the Odlo Natural + Kinship Warm Long-Sleeve and Black Diamond Solution as slightly more insulated options that still prove themselves remarkably well during the shoulder seasons.
Comfort and Fit
When choosing between options, comfort and fit are usually at the top of the list for many consumers. Even if a layer excels in all other categories, but fits you poorly or is uncomfortable, it won't serve you in your quest to send. This may be the toughest metric to rate because comfort and fit are ultimately subjective and are different for everyone's preferences and body type. We try our best to give as subjective of an opinion as possible when considering all the factors that play into a layer's comfort and fit. We scrutinize each layer and ask the following questions: How does the fabric feel next to your skin? Is it soft, itchy, stretchy, static, warm, or cool? Does it glide against your skin or cling too tightly?
Secondly, we consider how the garment generally fits: Is it too loose, too tight, does it constrict in particular areas — like the shoulders? How are the lengths of the torso and sleeves - does it expose your belly and wrists when reaching up? How are the cuffs? Are they too tight? Do they stretch out and lose shape when worn pulled up on your forearm? Is the neck comfortable? Is it loose, letting cold air draft in like a barn door, or is it too tight? What about mobility? Does the fabric have stretch? Are there gusseted underarms, purposeful stitching patterns, or articulated zones to help freedom of movement?
This long list of critiques provides us with a lot of information to justify how each layer will fit and perform. We're only human, so often we gravitated toward tops that are soft and comfortable next-to-skin. The comfiest layers are the Patagonia Capilene Air, SmartWool Merino 250, Ortovox 185 Rock'N'Wool, and the Outdoor Research Alpine Onset. A surprising turn-out concerning comfort is the NW Alpine Spectra — this top is a full-synthetic blend that magically feels like merino wool, thanks to the extra-pliable Spectra fibers.
We prefer tops with sleeves that don't tend to creep up our arms, and ones with a longer torso that avoids the always undesirable belly exposure. Slim-fitting sleeves and waists, combined with well-stitched hems and cuffs, tend to do the best. The tops that really do a great job of balancing fit and comfort are the SmartWool Merino 250, Patagonia Capilene Air, Icebreaker 200 Oasis, and the Patagonia Capilene Cool Lightweight. The Black Diamond Solution also fits this mold and is the only layer to incorporate thumb loops.
Quality of construction and thoughtful seam patterns are nice design touches that increase comfort as well as mobility. We appreciate the fit of the Icebreaker 200 Oasis, the Patagonia Capilene Cool Lightweight, and the NW Alpine Spectra. The well-articulated seam patterns of the Outdoor Research Echo L/S and Black Diamond Solution pull seams down from the shoulders — where they often rub under the weight of a backpack — and both tops add an extra side panel for increased upper-body mobility.
Some tops in our selection stand out for their superb comfort and fit, while a couple leave much to be desired. The Champions of Comfort are easily the SmartWool Merino 250, Patagonia Capilene Air, and Ortovox 185 Rock'N'Wool, all boasting soft, plush, cushy fabrics. Struggling in this category is the Helly Hansen Lifa Stripe, with a tight neck, super short torso, and thick sleeve cuffs. We also aren't impressed with the Smartwool Intraknit 200's fit, which has unusually long arms, uncomfortably narrow shoulders, and tight-fitting biceps.
Durability is a characteristic that we search for in all of our outdoor gear. We often spend on high-quality products to own fewer things that will both last us longer and stay out of the landfill. Base layers should adhere to the same purchasing ethics that we apply (or should apply) to all of our consuming habits. Buy less. Buy quality. Repair when possible. When that's not possible, opt for post-consumer products — many of the polyester layers included in this review are at least made in some part with recycled fibers.
To test durability, we inspect the strength of the fabrics and the quality of the stitching and construction of the pieces as a whole. We also drag them up against rocks, roll them in the dirt, bushwack through manzanita and chaparral to get to beautiful places and subject them to merciless amounts of washing and drying cycles. To test abrasion resistance in a controlled environment, we grind the elbows of the fabric a set number of times across a one-foot distance of gritty sandstone to see how the fabrics fair (think wash-board technique). This specific test gives us a very clear idea of how certain tops will hold up to abrasion.
The broad consensus is that merino wool is, generally speaking, less durable than synthetic fabrics. Yet in our abrasion test, the thick fabric of the SmartWool Merino 250 Crew displays only surface wear. The thickness of the wool is directly correlated to its durability level, and factors such as quality of production and materials can also affect the durability of a garment. Other factors that contribute to staying-power are flatlock seams, which you will find featured on the majority of the layers in this review.
Merino wool and silk, historically, are notorious for their lack of durability. Both tend to wear holes through quickly and/or shrink and lose their shape after repeated washings. Merino wool has come a long way in terms of durability — particularly considering merino wool/polyester blends. But when it comes to longevity, natural material still falls behind its 100% synthetic counterparts. For a lot of folks, the performance benefits of merino wool outweigh the lack of durability, and if you take proper care of your merino top, it can serve you for a long time. Despite its reputation as being a relatively short-term fabric, several of our testers have gotten many years of use out of their merino wool tops. That said, they try to be careful to hang dry them and not wear them every single day (they are certainly comfortable enough to want to do just that in the winter).
The shortest path to the grave for both merino wool and silk is through tumble drying. In fact, most manufacturers indicate that their wool layers are not dryer safe and instead suggest lying the garments flat to dry. Merino wool fibers are naturally antibacterial, which conveniently pairs with their natural ability to wick sweat and dry quickly. This fabric holds an uncanny power to resist body odor, whereas synthetic fabrics are infamous for holding onto and sometimes even enhancing stink. This means that wool can be worn more and washed less, increasing its longevity.
If you'll be wearing this top to scrape through slot canyons and drag yourself up rock chimneys, then durability is probably a quality you're going to want to think about first. As the only company in the world currently using this innovative fiber in clothing, the NW Alpine Spectra stands far above all others in this review in terms of durability. In our abrasion tests, we could barely get this top to show signs of wear. Throughout testing, its performance seemed to back the strong claims made about this fabric fiber technology.
Staying dry is a foundation of being comfortable in the outdoors. Not only can a sopping top severely inhibit your ability to find happiness and joy, but it can also be downright dangerous under the right conditions. Sometimes the moisture comes from outside sources, like rain or snow. Other times, it comes from a deep well of desire to work hard and push yourself, rising up to the surface as sweat. No matter where it comes from — physically or metaphorically — a top's ability to dry quickly on the body is important.
It's worth addressing that the drying speed of a fabric can differ depending on whether it is being worn or left out to dry. But based on our collective experience, we do expect a strong correlation between drying speeds and breathability — that is, tops that dry faster on the clothesline also tend to dry faster on our bodies. The Outdoor Research Echo L/S is a perfect example of this, flat drying in as little as a half-hour, and simultaneously preventing moisture build-up on our skin, regardless of climate or body temperature. But, of course, there are exceptions to this rule. The REI Silk Crew, with its ultra-lightweight design, had the fastest flat drying time. However, when it comes to breathability and drying out during activity, silk falls far behind rival synthetic materials.
Our drying speed test is a simple one. We fully saturate all of the products and then lay them out to dry at the same time, recording the time it takes for each layer to surface dry, as well as the time it takes for them to dry completely. Merino wool claims that it can absorb up to 30% of its weight in moisture before feeling wet to the touch. This seems reasonable, as we have to agitate and compress the wool layers while submerged for the fibers to become saturated — a plus if you are planning to wear these layers standalone in wetter, more mild climates. The Merino wool/polyester blends of the Patagonia Capilene Air and Smartwool Intraknit 200, in particular, do a great job at resisting absorption.
To no one's surprise, thinner fabrics dry significantly faster than thicker ones. As mentioned above, the REI Silk Crew dries lightning-fast, closely followed by the Outdoor Research Echo L/S and the Patagonia Capilene Cool Lightweight. Coming in close behind with admirable dry times for synthetic layers are the Helly Hansen Lifa Stripe and NW Alpine Spectra. Notably, the merino wool Icebreaker 200 Oasis dries quicker than the other wool layers of similar weight.
The ability to layer well is an often overlooked consideration but is important for practical use in the outdoors. One of the greatest qualities of a base layer is its versatility to be worn as a standalone top or to be layered in a myriad of ways to keep you warm and comfortable in any temperature or situation.
To test layering ability, we consider all the ways a top can be layered, and we try all of the combinations with every piece. We note how easy they layer as well as how they fit and feel: next to skin, over a t-shirt, over another base layer, under a sticky and tight fleece mid-layer, a sweatshirt, a puffy, a rain shell, as well as stacked in a full layering system of first (base) layer, mid-layer, puffy, and hard shell. While all of these layers perform well next to skin, a few work great layered in other ways, too.
The most form-fitting layer next-to-skin is the Odlo Natural + Kinship Warm Long-Sleeve, and not far behind are the Icebreaker 200 Oasis and Black Diamond Solution. While the REI Silk Crew is awkwardly baggy, its sheer construction allows it to layer easily underneath practically anything, including heavier-weight options. Looser, more relaxed fitting tops that layer well over another lightweight shirt are the Smartwool Merino 250 and the Meriwool Midweight Thermal.
With such a wide array of options out there, it can be tough to narrow your search down to the layer that best suits your body type, internal temperature inclination, and intended uses. We conduct all of our tests and summarize our experiences to try and help you choose the layer that will become your adventure sidekick for years to come. It's important for you to consider the activities, temperature ranges, features, and qualities when choosing a new base layer top. We wish you luck in your honorable pursuit of having fun outside.
— Aaron Rice and Roland Mott
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