The world's most in-depth and scientific reviews of outdoor gear

The Best Base Layers of 2019

Wake up and be awesome! This top was one that slept comfortably (if you tend to sleep on the warmer side) and carried us right through the heat of the day.
Friday November 15, 2019
  • Share this article:
Our Editors independently research, test, and rate the best products. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Learn more

Looking for the best base layer top for your well-chilled adventures? We sifted through 50+ of the top products of 2019 before testing 10 of the best side-by-side. In our testing, we dragged them to the tops of desert towers, skinned across wind-blown ridges, rowed down rivers, pedaled and ran through the mountains, and slept everywhere from the frozen desert dirt to our friends' floors. Our forays helped us rate which ones are best suited for different activities, from technical climbs to cozy hangs, and break it all down to help you decide which is the best to keep you warm and dry throughout the seasons.

Related: The Best Base Layers for Women of 2019


Top 10 Product Ratings

Displaying 1 - 5 of 10
≪ Previous | Compare | Next ≫
 
Awards Editors' Choice Award  Top Pick Award  Best Buy Award 
Price $87.96 at Backcountry
Compare at 3 sellers
$129.00 at REI
Compare at 3 sellers
$79.00 at Backcountry$62.31 at Backcountry
Compare at 3 sellers
$55.00 at REI
Compare at 3 sellers
Overall Score Sort Icon
100
0
76
100
0
74
100
0
71
100
0
70
100
0
68
Star Rating
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
  • 1
  • 2
  • 3
  • 4
  • 5
Pros Excellent temperature regulation, cozy comfy feel, very warm, breathable, doesn’t hold odor.Lightweight, insanely comfy, warm, breathable, versatileDurable, lightweight, handles a wide range of temperaturesComfortable, nice fit, breathable, versatile, quick to dry, odor resistantUltralight, airy and breathable, affordable, up to 100% recycled polyester
Cons Expensive, not the most durable, heavy when wetSuper expensive, extremely poor durabilityBulky seams, not as stink-resistant as other merino blendsExpensive, lack of durability, heavy when wetNot a warm layer by itself, loose-fitting cuffs can get caught up when layering
Bottom Line Our Editors’ Choice scores high across every metric making its way into our hearts as a favorite, keeping us warm, dry, and comfortable in any situation.This extra plush, comfortable, merino/polyester blend boasts extreme warmth while maintaining a hard to believe level of breathability, earning an OutdoorGearLab Notable Mention.Our Top Pick as a lightweight layer for aerobic activity, this top skillfully utilizes a Merino/polyester-blend to magically wick away moisture.Although not an award winner, this 100% merino wool top does a great job balancing warmth with breathability to bring you a solid, year-round workhorse.A high-value piece whose breathability and airy fit means that it can be worn for high-output activity regardless of the season, but not your go-to layer for mid-winter warmth.
Rating Categories SmartWool Merino 250 Crew Patagonia Capilene Air Crew Norrona Equaliser Icebreaker 200 Oasis Long-Sleeved Capilene Cool L...
Warmth (25%)
10
0
9
10
0
8
10
0
5
10
0
7
10
0
4
Breathability (20%)
10
0
7
10
0
8
10
0
9
10
0
7
10
0
9
Comfort And Fit (20%)
10
0
8
10
0
9
10
0
6
10
0
7
10
0
8
Durability (15%)
10
0
7
10
0
4
10
0
8
10
0
6
10
0
7
Drying Speed (10%)
10
0
5
10
0
7
10
0
9
10
0
8
10
0
7
Layering Ability (10%)
10
0
8
10
0
7
10
0
7
10
0
7
10
0
6
Specs SmartWool Merino... Patagonia Capilene... Norrona Equaliser Icebreaker 200 Oasis Long-Sleeved...
Material 100% merino wool 51% merino wool/49% recycled polyester 47% merino wool, 33% recyled polyester, 20% polyester 100% merino wool 100% double knit polyester (37% recycled, heather-colors; 100% recycled, solid-colors)
Fabric Weight 250 g/m² 190 g/m² 135 g/m² 200 g/m² 77 g/m²
Weight (size M) 9.2 oz 6.6 oz 5.5 oz 7.7 oz 3.8 oz
Types available crew, 1/4 zip, hoody, pullover crew, hoody t-shrit, crew, 1/4 zip crew, short sleeve, half zip long sleeve, t-shirt
Thumb Loops? No No No No No
Air Dry Test (minutes) 50 40 25 35 30
Fit Slim fit Slim fit Slim fit Slim fit Slim fit
Stitching Flatlock seams Seamless 3D construction Flatlock seams Flatlock seams Flatlock seams
Dryer safe? Yes Yes No No Yes
Shoulder top seams? No No No No Yes
Drop tail hem? No No No Yes Yes

Best Overall


SmartWool Merino 250 Crew


Editors' Choice Award

$87.96
(12% off)
at Backcountry
See It

76
OVERALL
SCORE
  • Warmth - 25% 9
  • Breathability - 20% 7
  • Comfort and Fit - 20% 8
  • Durability - 15% 7
  • Drying Speed - 10% 5
  • Layering Ability - 10% 8
Materials: 100% Merino Wool | Weight: 9.2 ounces
Cozy, cush feel
Regulates temperature well
Extremely warm
Versatile style, with little stink-factor
Heavy when wet
Not super durable
Sizing runs a bit large

We call this top the Cadillac of Cush. The Smartwool Merino 250 Crew offers a thick plush material made of 100% merino wool fibers that will immediately climb the ladder to become your beloved go-to layer. Outside of its superior comfort, it has found its way into the hearts of our testers and wins our Editors' Choice Award due to its versatility, excellent ability to regulate temperature, and stink-free factor. We've worn it for days on end while in the backcountry, and unlike its synthetic competitors, it was still very acceptable, stench-wise. It performs in a wide range of temperatures allowing you to comfortably transition from static cold to high output in warmer temps, all while staying comfortable and not building up a stink.

We do wish this top was a bit more durable through wear and washings, but that's part of the tradeoff for the goodness wool tops provide. The other downsides are that it is a bit heavy for lighter weight endeavors, heavy when wet, and slow to dry when the fabric becomes saturated. All in all this layer performs beautifully in almost every scenario that requires a warm and breathable base layer and is comfortable enough to wear every day. If you're looking for a comfortable do-it-all layer to follow you down the slopes, across ridge traverses, as well as to the grocery store, the SmartWool Merino 250 is tough to beat.

Read review: SmartWool Merino 250 Crew

Best Bang for the Buck


Patagonia Long-Sleeved Capilene Cool Lightweight


68
OVERALL
SCORE
  • Warmth - 25% 4
  • Breathability - 20% 9
  • Comfort and Fit - 20% 8
  • Durability - 15% 7
  • Drying Speed - 10% 7
  • Layering Ability - 10% 6
Materials: Up to 100% Recycled Polyester | Weight: 3.8 oz
Ultra-lightweight
Airy, relaxed fit
Great price
Very breathable
Not very warm
No more thumb-loops
Thin material susceptible to dropping stitches

If you are looking for a base layer at a more reasonable price-point for a shirt that will serve you well through at least 3-seasons, the Patagonia Capilene Cool Lightweight is a valuable, versatile layer to add to your collection. This ultra-lightweight layer is at the far end of our warm spectrum, but it was not designed to keep you cozy during the mid-winter months — unless you have a habit of running up mountains at SkiMo race paces. Instead, this layer was meant to keep you dry and moving through the other seasons, whether you are running, riding, or climbing.

As a stand-alone layer, the Capilene Cool Lightweight material hardly stands up to much more than an early-autumn chill. But this was one of our favorites for shoulder-season backpacking, and also does a great job pulling double-duty as a sun shirt. While we wished designers had left the thumb-loops in place, the silk-like feel of this layer still makes it easy to layer over, even if you occasionally lose a sleeve to the particularly grabby fleece of your favorite mid-layer.

Read review: Patagonia Long-Sleeve Capilene Cool Lightweight

Top Pick for Lightweight/Aerobic Activity


Norrona Equaliser


Top Pick Award

$79.00
at Backcountry
See It

71
OVERALL
SCORE
  • Warmth - 25% 5
  • Breathability - 20% 9
  • Comfort and Fit - 20% 6
  • Durability - 15% 8
  • Drying Speed - 10% 9
  • Layering Ability - 10% 7
Materials: 47% merino wool, 33% recyled polyester, 20% polyester | Weight: 5.5 oz
Incredibly moisture wicking
Durability
Lightweight warmth
Irritating for some next-to-skin
Not as stink-resistant as other merino/synthetic blends

A top performer in almost any condition — just as long as you keep your heart rate up — the Norrona Equaliser offers a merino-poly blend that seems to absorb and eliminate sweat magically. With a balance of warmth that just slightly outperforms its lightweight design, we found ourselves reaching for this as a layer for early morning runs and afternoon bike laps. Our Top Pick for aerobic activity is not a stand-alone layer for mid-winter warmth, but will certainly keep you comfortable and dry in the skin track.

Norrona might not be a household name in the US market, but they have been making technical clothing to stand up to the rugged Norwegian backcountry for almost 100 years. The snug, European-cut of this layer might not be the right fit for some, but thoughtful flatlock stitching helps increase mobility in the places we found the Equaliser to fit tightest — particularly in the arms and shoulders. But factor in bomber durability, and you might have found that new layer that can stand up to any 3-season, type-2-fun adventure you can dream up.

Read review: Norrona Equaliser

Notable for Overall Performance


Patagonia Capilene Air Crew


74
OVERALL
SCORE
  • Warmth - 25% 8
  • Breathability - 20% 8
  • Comfort and Fit - 20% 9
  • Durability - 15% 4
  • Drying Speed - 10% 7
  • Layering Ability - 10% 7
Materials:51% Merino Wool, 49% Recycled Polyester | Weight: 6.6 ounces
Super cozy and comfy feel
Extremely warm
Low weight for the warmth
Highly breathable
Expensive
Very low durability

We've never seen a base layer quite like this, well, because there's never been one. Patagonia's innovative technology with their new Capilene Air leaps into the future of what first layers are capable of, and we're singing their praises. The softness and next-to-skin comfort are unparalleled, the mobility and seamless design are unbeatable, and the coziness factor is rivaled only by the SmartWool Merino 250 Crew. We want to live in it, to fall and love, and grow old in it. Layered within a system, it provides warmth for the deepest reaches of winter, but the nearly see-through material breathes like a marathon-running monk.

The glaring thorns in the side of this high performing and versatile base layer come in the form of price and durability. It is the most expensive layer we tested. This top is not built to be dragged up chimneys and through slot canyons, its abrasion resistance is sad at best. Cost versus durability makes this a tough top to justify with other great models out there for much less money and significantly higher strength. We hope Patagonia improves the longevity of the Capilene Air, which would make it next level.

Read review: Patagonia Capilene Air


A pile of warmth welcoming a fresh dusting of winter snow.
A pile of warmth welcoming a fresh dusting of winter snow.

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 the past 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 — in the winter 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.

The Merino 250 gives us everything we want in a base layer.
The REI Co-op Merino Midweight out for an evening stroll.

Six key metrics were identified as essential to grade a base layer top effectively - Warmth, Breathability, Comfort/Fit, Drying Speed, Durability, and Layering Ability. For each of these, an appropriate field and lab test was developed and carried out. For metrics such as warmth, testing was as straightforward as wearing the garments in cold weather often and noting the relative differences. Other metrics, like durability, called for a combination of field use (i.e., chimney climbing) and lab testing (repeated dry and wash cycles). From the high desert of the US Southwest to the Pacific Northwest, we took these tops out on all the activities we love — mountain biking, uphill and downhill skiing, trail running, backpacking, and more — testing and assessing along the way.

Related: How We Tested Base Layers

Analysis and Test Results


As your go-to workhorse for sweat management, we understand the importance of having a top that will serve you well through all of your outdoor pursuits. That's why we tested the heck out of what determined to be the best ten base layer tops on the market. By submitting them to everyday use, a variety of outdoor activities, and across a spectrum of temperatures and environments, we built a picture of what types of layers work best and when. We dialed-in the most important qualities of base layer tops, and tested them side-by-side within these metrics to bring you the most in-depth, most helpful reviews on the internet to help you navigate purchasing the best one for your needs.

Related: Buying Advice for Base Layers

This high-value Capilene Cool top from Patagonia stands out in terms of breathability  but still provides just enough warmth to keep you pushing uphill  even in the long shadows of the evening.
This high-value Capilene Cool top from Patagonia stands out in terms of breathability, but still provides just enough warmth to keep you pushing uphill, even in the long shadows of the evening.

We scored each layer across our six metrics and compiled a total score out of 100 for each product. It is important to note that these scores are determined relative to the other products in the review — we purposefully chose ten of 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 it performed poorly in relation to the competition. By testing and rating each model side-by-side across these metrics, we help you to easily find the shirt(s) that score high in the categories that are significant for how you intend to use it. We describe how we tested each metric and our experiences with each layer.


Value


The balance between price and value is always a fine line to walk when researching a product. Merino wool tops are typically more expensive than synthetic, but offer benefits like superior body-temperature regulation, moisture-wicking ability, and odor resistance. Synthetic fabrics are cheaper, but are sometimes not as soft next-to-skin, often hold moisture — so tend to hold stink longer — and often don't provide the same warmth-to-weight when compared to their natural-fiber companions.

The arguments of synthetic vs. all-natural fibers is a perpetual battle in the world of base layers. We like to think of ourselves conscious objectors to this fight. Through our testing, found the Patagonia Capilene Cool Lightweight to be the most valuable base layer out there. A standout for 3-season recreation and as an athletic base for the coldest months, this top is not only versatile for activities such as backpacking but performs impressively well when properly layered over on an alpine ascent. If you're value-minded but run colder, add a little warmth with options like the REI Merino Midweight or Arc'teryx Phase AR — two choices that are beefier layers, but are a little more reasonably priced than similarly-weighted competitors.

Less  sometimes  is more -- if you're looking to go fast-and-light on your next backpack  think about investing in good base layers that can be worn in a wide-range of temperatures  and allow you to ditch some of your bulkier clothing when the season permits.
Less, sometimes, is more -- if you're looking to go fast-and-light on your next backpack, think about investing in good base layers that can be worn in a wide-range of temperatures, and allow you to ditch some of your bulkier clothing when the season permits.

One of the best ways we believe to determine value is to start with the question: how do I intend to use this particular layer? Do I want something that will keep me warm during the darkest months of winter? Or do I want something to run in when temperatures start to taper off in the fall? These types of questions will help guide you in the direction of what holds more importance for you as a buyer, ultimately helping you be a better-informed consumer. Decide which metrics are most important for your sport or activity, whether it's ice-climbing or shoveling snow in your driveway.

Warmth


Warmth is one of the most important qualities when choosing your first layer. As the foundation of your layering system, the warmth of a top doesn't just lie in the thickness of the fabric or its ability to trap your body heat but in the multi-dimensional capabilities to regulate temperature. This means not only holding heat to keep you warm in colder temperatures but also allowing excess heat to escape when temps rise or your heart rate climbs. It also involves wicking away sweat from your skin to the external environment to keep you dry. All of these ingredients are essential in a product's ability to keep you warm and dry in varying temperatures and situations. A top that may be extremely warm but doesn't breathe well and holds onto moisture may work for ice fishing but will leave you dangerously wet and cold during high-output, start/stop activities like backcountry skiing.


To test the diverse range of qualities a product must exhibit to be successful in keeping you warm, we wore these layers through the varying temps of fall and winter. We brought them along with us as we skinned up windblown ridges in the Northwest, rowed through desolate canyons in the southwest, slept on frozen dirt after climbing sunny sandstone cracks in the desert, and explored trails by bike and foot in Colorado and New Mexico. Our highest scoring tops for warmth are the SmartWool Merino 250, the Patagonia Capilene Air, and Smartwool Intraknit 200. These tops consist of thicker, cushy fabrics that seal in heat while maintaining excellent breathability and wicking qualities.

While not always the case for synthetic tops  we find that with base layers knit with either full Merino wool or a Merino-blend  the heavier the garment  the warmer it tends to be.
While not always the case for synthetic tops, we find that with base layers knit with either full Merino wool or a Merino-blend, the heavier the garment, the warmer it tends to be.

What is the level of warmth for you? Depending on what you use it for, a super warm top may not be what best suits you. A really warm layer is great if you are out in extremely cold conditions, participating in activities that don't work up much of a sweat, or if you normally run on the chilly side. For the deep cold of winter, we recommend the SmartWool Merino 250, our heaviest weight, 100% merino layer. What is great about this top is that it's not limited to only frigid temps. We love this top for most of the fall and spring, too, and have been happy to have it on mid-summer high altitude, windy missions, too.

Early bird gets the worm  or a summit bid all to ourselves in this case. The boys all wore different weights of merino wool baselayers on this climb up Mt. Hood.
Early bird gets the worm, or a summit bid all to ourselves in this case. The boys all wore different weights of merino wool baselayers on this climb up Mt. Hood.

If you find yourself in cool temps, participating in high aerobic activities, or want versatility across seasons - choosing a model with a lower warmth rating and a higher breathability rating may benefit you. For cross-country and backcountry skiing or fall mountain biking, a lighter weight layer that excels at breathability like the Patagonia Capilene Cool Lightweight or the Helly Hansen Lifa Stripe may be just what you're looking for. If you're a rock-climber anticipating long-belay stances and short bursts of energy, check out the Capilene Air and Icebreaker 200, two tops that provide a solid level of warmth, but are still highly breathable. It's smart to consider what temperature ranges and activities you'll be wearing your top for, and choose one that works best for your passions.

Looking to cut the chill  but having trouble getting that campfire going? Grab a base layer to keep you cozy  while you and your friends debate the pros and cons of the tee-pee vs. the log-cabin.
Looking to cut the chill, but having trouble getting that campfire going? Grab a base layer to keep you cozy, while you and your friends debate the pros and cons of the tee-pee vs. the log-cabin.

There are some specific features that we've found helped keep us warm and may help you in your search for the perfect base layer. Models like the Smartwool Merino 250, Patagonia Capilene Air, Icebreaker 200 Oasis, Smartwool Intraknit 200, and the REI Co-op Merino Midweight have nice long arms and a drop-tail hem. These design features allow them to stay tucked into your bottoms when skiing. They also keep them from rising up and exposing your wrists, back, and belly when bending over to put on your skins or reaching for that next crimper when climbing. We found the shorter torso on the Helly Hansen Lifa Stripe leaves our bellies exposed to the biting winds when reaching overhead. The tightly woven synthetic fabric of the Arc'teryx Phase AR did a great job with wind resistance compared to other models when worn as a stand-alone layer, but didn't breathe as well when incorporated in a layering system.

Making our way down from the summit of Mt. Hood during a winter ascent. This climb is a true test of a base layer. Skinning and sweating in pre-dawn subfreezing temps for hours  then standing still on the windy summit  and finally 6 000 feet of downhill skiing. The Smartwool 250 rules in these environments.
Making our way down from the summit of Mt. Hood during a winter ascent. This climb is a true test of a base layer. Skinning and sweating in pre-dawn subfreezing temps for hours, then standing still on the windy summit, and finally 6,000 feet of downhill skiing. The Smartwool 250 rules in these environments.

There's a lot to consider when finding the base layer that works best for you. Thinking about the temperatures and types of activities you're participating in, combined with knowledge of fabric and features will allow you to find a top that will soon become an essential part of your quiver!

There are significant differences between a natural fiber (Merino wool) and a synthetic fabric (polyester, polypropylene) when it comes to warmth. The key here is that they both continue to insulate when wet.

Breathability


Breathability is the yin to warmth's yang-- alongside warmth, it is arguably the most important quality of a quality base layer. Breathability is tied to moisture-wicking and is effectively the ability of a fabric to collect the moisture (sweat) that we all produce during activity, and move that moisture to the outside surface of the layer, where it can freely evaporate. The efficiency and speed that a fabric can convert sweat to water vapor will determine how breathable the garment is. A quality, breathable layer will help regulate your internal body temperature through wide ranges of environmental temperatures and a spectrum of energy outputs. This means it will effectively work to keep you dry and warm, or dry and cool, depending on what you need.


Breathability is an extremely important quality during active pursuits, as well as stop/start activities, like backcountry skiing. A breathable shirt will allow the moist air produced from perspiration to escape through the material and into the outside environment without saturating the fabric, thus keeping you warm and dry. A non-breathable shirt will prevent the moisture from escaping, causing it to condense on the inside of the garment. A non-breathable first layer would be miserably sweaty, wet, heavy, and therefore dangerous in cold conditions.

Casual alpine cows. The Patagonia Capilene Cool Lightweight long-sleeve is a great option for warm-weather backpacking.
Casual alpine cows. The Patagonia Capilene Cool Lightweight long-sleeve is a great option for warm-weather backpacking.

In addition to our assessment throughout months of use hiking, running, skiing, climbing, and biking, we also designed a test to assess each layer's breathability systematically. In a temperature-controlled, indoor environment, we worked up a sweat with the same short, rigorous exercise routine, consisting of pull-ups, push-ups, mountain climbers, burpees, and jump squats. We tested each layer side-by-side, and then timed how long it took for our skin and the inside of our shirts to dry after stopping.

The Patagonia Capilene Air proving its versatility  keeping us cool and comfortable in the fall Utah Sun. Its nearly see-through fabric allows for air to pass through it with ease making it extremely versatile for conditions ranging from super cold when layered  to warm weather as a stand-alone layer.
The Patagonia Capilene Air proving its versatility, keeping us cool and comfortable in the fall Utah Sun. Its nearly see-through fabric allows for air to pass through it with ease making it extremely versatile for conditions ranging from super cold when layered, to warm weather as a stand-alone layer.

The tops that earn our highest scores for breathability were also — not surprisingly — the lightest weight fabrics that didn't score highly in terms of warmth. Those were the Patagonia Capilene Cool Lightweight, Helly Hansen Lifa Stripe, and Norrona Equaliser. The Patagonia Capilene Air impressed us with its unique ability to score extremely well in both warmth and breathability ratings! The SmartWool Merino 250, Intraknit 200, and Icebreaker 200 Oasis all scored similarly in this test. All three of these layers clock in at relatively the same material weight — are we seeing a connection between weight and breathability?

It's all about moisture-wicking -- pulling sweat away from your skin and up to the outer-layer of the garment  where it can easily evaporate -- keeping you comfortable  even when working your hardest.
It's all about moisture-wicking -- pulling sweat away from your skin and up to the outer-layer of the garment, where it can easily evaporate -- keeping you comfortable, even when working your hardest.

While this teleconnection holds true for many full-Merino tops, the lowest performers in the breathability category were the Arc'teryx Phase AR and The North Face Warm. Both are made of synthetic materials, are a heavier weight, and a tighter weave, qualities that tend to increase warmth but decreases their breathability. On the bright side, these qualities do allow them to be more wind resistant as a stand-alone layer than their more breathable counterparts.

For its moisture wicking ability and durability  we loved the Norrona Equaliser as a cool-weather alternative to our normal mountain bike jersey.
For its moisture wicking ability and durability, we loved the Norrona Equaliser as a cool-weather alternative to our normal mountain bike jersey.

Comfort and Fit


When choosing a base layer, comfort and fit are usually at the top of the list for many consumers. Even if it 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 different for everyone's preferences and body types. 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 scrutinized each layer and asked 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 hug you like your overly-touchy Aunt Glenda?

This top is impressively warm for its weight - what you can't see  is that our buddy is climbing in a puffy - while we had no problem hanging out for long-belays in the shade.
This top is impressively warm for its weight - what you can't see, is that our buddy is climbing in a puffy - while we had no problem hanging out for long-belays in the shade.

Secondly, we considered 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, and is trying to choke you out like a UFC fighter? What about mobility? Does the fabric have stretch? Are there gusseted underarms, purposeful stitching patterns, or articulated zones to help freedom of movement?


Armed with this ridiculously long, but ridiculously scrutinizing list of questions to critique each layer, we learned a lot about how a layer will perform. We're only human, and gravitated toward tops that were soft and comfortable next-to-skin. The comfiest layers are the Patagonia Capilene Air, SmartWool Merino 250, REI Co-op Merino Midweight, and the Patagonia Capilene Cool Lightweight Crew. The least comfortable against the skin is the tight-knit synthetic fabric of the Arc'teryx Phase AR, and the similarly tight-knit Merino-blend of the Smartwool Intraknit 200.

The Patagonia Capilene Air's soft  stretchy  and airy fabric made it a favorite for comfort among the testers. It's a layer that we've found difficult to take off whether we're skiing or watching a movie at home.
The Patagonia Capilene Air's soft, stretchy, and airy fabric made it a favorite for comfort among the testers. It's a layer that we've found difficult to take off whether we're skiing or watching a movie at home.

We prefer tops with sleeves that don't tend to creep up our arms, and a longer torso that avoids the always undesirable belly exposure. Slim fitting sleeves and waists, combined with well-stitched hems and cuffs tended to do the best. Tops that both fit the best and were the most comfortable are the SmartWool Merino 250, Patagonia Capilene Air, Icebreaker 200 Oasis, and the Patagonia Capilene Cool Lightweight. Performing the most poorly in this category was the Helly Hansen Lifa Stripe with an extremely short torso, resulting in belly exposure that was at an all-time high. Not far in front of that was the Smartwool Intraknit 200, whose tight-fitting arms and shoulders were in no way benefited by the stretch and engineered-articulation of the material.

Fit of the Smartwool Intraknit: very long arms (see bunching)  very long torso  overall tight fitting. Our tester is 5'10"  160lbs wearing a size medium
Fit of the Smartwool Intraknit: very long arms (see bunching), very long torso, overall tight fitting. Our tester is 5'10", 160lbs wearing a size medium

Quality of construction and thoughtful seam patterns were nice touches that increase comfort as well as mobility. We appreciated the fit of the Icebreaker 200 Oasis and the Patagonia Capilene Cool Lightweight, and the seam pattern of the Norrona Equaliser that isolated the upper arms and shoulders from the torso was particularly nice feature of articulation.

Two flatlock seams isolate the shoulders and back from the torso  a thoughtful  articulated design that increases mobility.
Two flatlock seams isolate the shoulders and back from the torso, a thoughtful, articulated design that increases mobility.

A few tops were able to stand out for their superb comfort and fit while a couple left much to be desired. The Champions of Comfort are easily the SmartWool Merino 250 and the Patagonia Capilene Air both boasting soft, plush, cushy fabrics. The North Face Warm is the most comfortable synthetic fabric we tested made with a thick and soft polyester material — on the thinner side, the Patagonia Capilene Cool Lightweight is sports a magical, almost silk-like polyester. The Arc'teryx Phase AR is impeccably constructed, has a great fit, and is extremely durable, but the tough synthetic material is not the most pleasant against the skin. Struggling in this category is the Helly Hansen Lifa Stripe, with a tight neck that chokes us out, super short torso, and thick sleeve cuffs. Similarly, the Smartwool Intraknit 200 didn't fare well here with unusually long arms and uncomfortably narrow shoulders and tight-fitting biceps.

If possible, we always suggest trying garments on in person as it is the only way to know whether it will fit you well, and saves you the time, hassle, and the carbon impact of shipping and returning.

This collage shows the wide range in fit among the tops we tested  from tight to baggy.
This collage shows the wide range in fit among the tops we tested, from tight to baggy.

Durability


Durability is a characteristic that we search for in all of our outdoor gear. We spend good money on high-quality products so that we may own fewer things that will last us longer, and thus stay out of the landfill. Base layers should adhere to the same purchasing ethics that we apply (or should) 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 some part recycled-polyester.


To test durability, we inspected the strength of the fabrics and the quality of the stitching and construction of the pieces as a whole. We also dragged them up against rocks, rolled in the dirt, plowed through manzanita and chaparral bushwacking to get to beautiful places, and subjected them to merciless amounts of washing and drying cycles. To test abrasion resistance in a controlled environment, we ground the elbows of the fabric a set number of times across a one-foot distance of gritty granite to see how the fabrics faired (think wash-board technique). This specific test gave us a very clear idea of how certain tops held up to abrasion. The most durable top we tested is the Arc'teryx Phase AR Crew. Its tough and tight-knit synthetic fabric performs above the rest when it comes to getting dragged around and beat up. Similarly, the merino/poly-blend of the Norrona Equaliser was seriously impressive, considering the material weight. The Patagonia Capilene Air is the least durable top overall that we tested — think fine, open-knit cashmere sweater — but performs exceptionally in all other categories.

Making its way up an Eldo classic  the SmartWool Merino 250 shows off its ability to breathe and keep you comfortable in warm conditions as well as cold. The thick merino fabric makes it the most durable merino layer that we tested.
Making its way up an Eldo classic, the SmartWool Merino 250 shows off its ability to breathe and keep you comfortable in warm conditions as well as cold. The thick merino fabric makes it the most durable merino layer that we tested.

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 showed only surface wear, whereas the synthetic fabric of The North Face Warm Crew now sports a hole through the fabric. The thickness of the wool directly correlated to its durability level, but factors such as quality of materials and construction 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.

The Arc'teryx Phase AR was by far the most durable top we tested. It wasn't the most comfortable next to the skin and also not as breathable as merino  but bulletproof when it came to dragging it up climbs.
The Arc'teryx Phase AR was by far the most durable top we tested. It wasn't the most comfortable next to the skin and also not as breathable as merino, but bulletproof when it came to dragging it up climbs.

Merino wool, historically, is notorious for its lack of durability, wearing holes through the fabric or shrinking/losing its shape through washes. Merino wool has come a long way in the durability that it offers — particularly considering merino-polyester blends, such as the fabric of the Equaliser. But when it comes to longevity, natural material still falls behind its 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 reputative 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 comfortable enough to want to in the winter!).

Merino wool's shortest path to the grave is through consistent washing, and particularly tumble drying of the garment. 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, paired with their incredible ability to wick sweat and dry quickly. This fabric holds an uncanny power to resist body odor, whereas synthetic fabrics are infamous for quickly holding onto and even enhancing stink. This means that wool can be worn more and washed less, increasing its longevity. We suggest only washing merino layers when they are visibly dirty and disgusting, or you manage to wear them enough for them to eventually stink.

The REI Co-op Merino Midweight showing its war wound after our abrasion test in the lab. This was the only 100% merino layer that developed a hole from our abrasion test.
The REI Co-op Merino Midweight showing its war wound after our abrasion test in the lab. This was the only 100% merino layer that developed a hole from our abrasion test.

If you'll be using your base layer 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. The Arc'teryx Phase AR for synthetics, the Norrona Equaliser for a blend, and the SmartWool Merino 250 for pure merino are the most durable tops we tested.

Although some few Merino wool garments give the OK to tumble dry on low, we suggest washing on a cold cycle and laying to flat dry. This will increase the longevity of your shirt.

Drying Speed


Staying dry is a foundation of being comfortable in the outdoors. Whether you need to cool down or stay warm, being wet can severely inhibit your ability to access happiness and joy. 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 — flat dry times and dry times on the body sometimes vary. We do expect, and often experienced a strong correlation between drying speeds when laid flat and when worn — that is, tops that dry faster on the clothesline also tend to dry faster on our bodies. The Norrona Equaliser was the perfect example of this, flat drying in less than a half-hour, and incredibly preventing moisture build-up on our skin, regardless of climate or body temperature level.

When the going gets tough  its important to have a base layer that will actively dry out on your body  so when the time comes to take a break  you're not left shivering in the shadows.
When the going gets tough, its important to have a base layer that will actively dry out on your body, so when the time comes to take a break, you're not left shivering in the shadows.

Our drying speed test was a simple one. We fully saturated all of the products and then laid them out to dry at the same time, then recorded the times it took for each layer to surface dry, as well as the time it took 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 seemed to prove true as we had 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, Norrona Equaliser, and Smartwool Intraknit 200 and the full synthetic fabric of theArc'teryx Phase AR also did a great job at resisting absorption. The synthetic fabric of The North Face Warm, on the other hand, happily lapped up water like a thirsty dog.

Tops during the dry speed test.
Tops during the dry speed test.

An obvious observation was that thinner fabrics dried significantly faster than thicker ones — big surprise, huh?! As mentioned above, the Norrona Equaliser dried lightning-fast, closely followed by the Patagonia Capilene Cool Lightweight. Coming in close behind with admirable dry times were the Helly Hansen Lifa Stripe as a synthetic layer, and the Icebreaker 200 Oasis, which dried quicker than the other Merino wool layers of similar weight. The slowest to flat dry were two of the synthetic layers, the Arc'teryx Phase AR and limping into last place was The North Face Warm, which took four times longer to dry than the fastest two.

All parties involved breathing hard through technical terrain. The breathability of this merino was sufficient enough to keep us dry when working up a sweat  but didn't stand out above the crowd.
All parties involved breathing hard through technical terrain. The breathability of this merino was sufficient enough to keep us dry when working up a sweat, but didn't stand out above the crowd.

Layering Ability


A base layer's 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 single layer when you need just a little something 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 thought of every way a top could be layered, and we tried all the combinations out on every garment. We observed how easy they layered as well as how they fit and felt: 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 layers performed well next to skin, a few did great in other areas also.

An example of a layering system. Base layer  fleece mid layer  soft shell  and down puffy. The Patagonia Capilene Air  pictured here  traps heat extremely well in a layering system but as a stand-alone layer  air cuts right thru it.
An example of a layering system. Base layer, fleece mid layer, soft shell, and down puffy. The Patagonia Capilene Air, pictured here, traps heat extremely well in a layering system but as a stand-alone layer, air cuts right thru it.

The most form-fitting layer next-to-skin is the Icebreaker 200 Oasis, and not far behind that the Norrona Equaliser. Looser, more-relaxed fitting tops that layered well over a shirt or another base layer are the Smartwool Merino 250, the Patagonia Capilene Cool Lightweight, and the REI Merino Midweight.

We're talking base layers here -- the start to any good cold-weather get-up. Base layers are designed to keep you dry and comfortable at skin level  below a mid layer to keep you warm  and a shell to keep you protected from the elements.
We're talking base layers here -- the start to any good cold-weather get-up. Base layers are designed to keep you dry and comfortable at skin level, below a mid layer to keep you warm, and a shell to keep you protected from the elements.

Conclusion


With such a wide array of options out there, it can be tough to narrow your search down to find the base layer that best suits your body type, internal temperature inclination, and intended uses. We conducted all our tests and collected our experiences into this review to try and help you choose the layer that will become your adventure sidekick for years to come! As we've stated before, it's important for you to consider the activities, temperature ranges, features, and qualities that you'll most utilize in a base layer top. We wish you luck in your honorable outdoor pursuits of fun!


Roland Mott and Aaron Rice