As your next-to-skin article of clothing, a baselayer plays a fundamental role in pulling moisture away from the body and regulating core temperature. It’s far easier to justify purchasing a nice down jacket, but a baselayer can be just as important for activities like skiing, hiking, and climbing. To start, avoid cotton (like the old adage “cotton kills”). You’ll need a fabric that won’t stay wet, and merino wool and polyester are the most common choices. Merino is ultra soft, warm, and handles moisture well, but is very expensive. Polyester blends are cheaper and more durable but aren’t as comfortable or resistant to odor. Below are our picks for the best baselayers of 2020. For more information, see our baselayer comparison table and buying advice below the picks. To complete your kit, we’ve also written about the best midlayers and ski jackets.
Material: 100% merino wool
Weight: 10 oz.
What we like: Extremely comfortable and functional.
What we don’t: Pure merino baselayers can have durability issues.
The Merino 250 ¼ Zip from Smartwool is the whole package in a baselayer: it’s super soft against the skin, offers the right amount of warmth, wicks moisture, and repel odors as well as any pair of long underwear can. It’s a great thermal option for skiing and even has a UPF 50+ rating for use as an outer layer during activities like hiking, biking, and running. We prefer the Zip Top version over the Crew, which allows for more ventilation when you’re working up a sweat.
The biggest issues with the Merino 250 are price and durability. If you add Smartwool merino bottoms, you’re looking at around $200 for your baselayers alone. And given that it’s made from 100 percent merino wool, it simply won’t last forever (proper care can help, but from our experience, merino almost always deteriorates after extensive use). If you’re looking for inexpensive thermals that will last for many seasons to come, grab a synthetic like the Patagonia Capilene below. But for the ultimate in comfort and performance, the Merino 250 from Smartwool is our top pick.
See the Men's Smartwool Merino 250 See the Women's Smartwool Merino 250
Best Synthetic Baselayer
Material: 100% recycled polyester
Weight: 6.2 oz.
What we like: Cheaper and more durable than merino wool.
What we don’t: Not quite as soft.
Choosing synthetics over merino wool has clear upsides, the most notable being cost and durability. For just over half the price of the Smartwool above, the polyester Capilene Midweight by Patagonia offers similar warmth and moisture-wicking capabilities. And it likely will last for many seasons—we have Capilene tops that are multiple years old and counting despite heavy use. Plus, it doesn’t hurt that Patagonia has upgraded the latest Capilene Midweight with 100-percent-recycled materials.
What do you sacrifice by going with a synthetic baselayer? Polyester is decently comfortable but not as soft against the skin, and it doesn’t regulate body temperature or repel odor quite as well as wool. This doesn’t mean that your Capilene will get stinky super quickly—and Patagonia has made strides in this area with an anti-odor HeiQ Fresh treatment—but you will find yourself putting it through the wash more often. However, not everyone wants to spend $100 or more on a baselayer, which is why we love Patagonia’s Capilene line. For less or more warmth, try the Capilene Lightweight and Thermal Weight versions.
See the Men's Patagonia Capilene See the Women's Patagonia Capilene
Best Budget Baselayer
Material: 100% polypropylene
Weight: 5.1 oz.
What we like: Wicks moisture well and a great value.
What we don’t: Not as warm as other baselayers on this list.
There’s a lot to like about this lightweight active baselayer from Helly Hansen. At just $40, it’s one of the cheapest options on this list yet still will keep you dry and decently warm in most conditions. The headliner is the Lifa fabric, which is made from Polypropylene and specializes in wicking moisture away from the skin (it does so much better than polyester). Along with a nice athletic fit, the Lifa Stripe is great for active skiers and other high-output activities like climbing and hiking.
The downside of Polypro compared to polyester or nylon is that it isn’t as warm. The Lifa Stripe Crew falls into our lightweight category, meaning that it provides some insulation but requires a good midlayer or insulated shell in cold conditions. It’s worth the tradeoff for many people who love the performance and value of this baselayer. And it doesn’t hurt that Helly Hansen made the look a little less boring than other options on the list, with some fun colors to choose from and a signature stripe design down the sleeve.
See the Men's Helly Hansen Lifa Stripe See the Women's Helly Hansen Lifa Stripe
Best Heavyweight Baselayer for Extreme Cold
Material: 100% merino wool
Weight: 17.6 oz.
What we like: Very warm and soft. A great value for an all-merino baselayer.
What we don’t: Because of the thickness and cut, it’s not ideal for high-output activities.
Woolx is a small New York-based company that doesn’t get the hype of a Smartwool or Icebreaker, but the thick Glacier LS is our favorite heavyweight baselayer. Made with 100 percent merino wool, this piece is much warmer and more substantial than the midweight and lightweight options on the list. And because it’s merino, it’s still soft against the skin and breathes well. We’ve used the Glacier LS for everything from skiing and snowshoeing to casual use and have come away very impressed.
To put things in perspective, in terms of thickness the Glacier LS is 400g/m², while the Smartwool Merino above is 250g/m². Both are 100 percent merino and both fall around the $100 price point (the Smartwool gets a $15 edge here at $105). This means that you’re getting much more baselayer for your money from Woolx compared to just about any other merino brand. One consideration is that the Glacier LS does not have a tailored fit like some other baselayers, so it’s more about warmth than anything else. We highly recommend it for downhill skiing in cold places, winter walking, and everyday wear.
See the Men's Woolx Glacier LS See the Women's Woolx Riley LS
Best of the Rest
Materials: 87% merino wool, 13% nylon
Weight: 6 oz.
What we like: A great option for cool days and travel.
What we don’t: Thin materials require more care.
We’ve already listed the Smartwool Merino 250 as our top pick, but we’d be remiss not to include another stellar baselayer in the 150 Crew. The build quality is similar: Smartwool adds 13 percent nylon to the mix for a boost in durability, the weight goes down significantly to 6 ounces (the lack of the zipper matters here too), and you get the same minimalist seams for comfort. Compared to the warm 250 above, the 150 is lighter in weight and ideal for uses like spring skiing, hiking in the shoulder seasons, and travel. You’ll feel like you are wearing much less baselayer, but the boost in coziness and moisture-wicking capabilities are still there.
It’s worth noting that for this winter, Smartwool split the difference in fabric weight and released the techy Intraknit Merino 200. This performance piece is nearly half polyester/elastane (it’s 53 percent merino), incorporates low-prolife seams, and has body mapping with mesh panels throughout for improved ventilation. We haven’t yet had the chance to give the Intraknit baselayer an extended test, but for high-output activities, it’s an intriguing new option from the market leader.
See the Men's Smartwool Merino 150 Crew See the Women's Smartwool Merino 150 Crew
Material: 100% merino wool
Weight: 8.5 oz.
What we like: A soft, stretchy, and well-made baselayer.
What we don’t: Pricey for an REI product.
Of all of REI Co-op’s in-house products, their merino baselayer is one of our favorites. It’s right on the same playing field as heavy hitters like Smartwool and Icebreaker, which is quite a feat given that those companies specialize in wool layering pieces. The REI midweight Half-Zip is soft, warm, has a good amount of stretch, and wicks moisture as well as any. And most importantly, it has handled everything from backpacking to cross-country skiing with ease.
Unlike many REI products, the Merino Midweight Half-Zip doesn’t come at much of a discount, which is why we have it ranked here. The $90 price tag and 200g/m² thickness are the same as Icebreaker's popular Oasis Crewe, although you do get a front zip and higher collar on the REI. And for just $15 more, you can get the legendary Smartwool Mid above, our top pick, which is slightly thicker and warmer at 250g/m². We really like the REI and have had nothing but positive experiences with it thus far, but we’re not ready to dethrone the Smartwool just yet.
See the Men's REI Merino Midweight See the Women's REI Merino Midweight
Materials: 81% merino wool, 12% nylon, 7% elastane
Weight: 6.9 oz.
What we like: Merino softness with added durability.
What we don’t: Expensive.
Arc’teryx always seems to take outdoor gear tech to the next level, and the new Satoro AR is a case in point. Everyone loves the softness of merino against the skin, but its durability has long been an issue. The Satoro attempts to solve the problem by using a nylon core with merino wrapped around the outside. The result is a baselayer that still offers premium next-to-skin comfort but is much tougher than pure merino.
Arc’teryx also paid attention to a number of small details with the Satoro AR. The cuffs are nicely tailored and long for additional warmth over the hands. Gusseted underarms increase mobility, and a laminated zipper pocket on the chest for men (arm for women) adds to its utility as an outer layer. The result is a premium baselayer at a premium price, and whether all that technology is worth it is up to you... Read in-depth review
See the Men's Arc'teryx Satoro AR See the Women's Arc'teryx Satoro AR
Materials: 90% nylon, 10% Spectra
Weight: 12 oz.
What we like: Durable enough to be worn as an outer layer.
What we don’t: Expensive for nylon.
NW Alpine certainly isn’t a household name, but this small Portland-based company designs and constructs alpine climbing apparel on par with the best. Although they only make a handful of items, each of their products is a study in quality over quantity. And their Fortis Spectra Hoody is a serious baselayer: it’s comfortable, warm and breathable, and has great overall durability. We’ve put their similar Spider Hoody through four years of climbing abuse—much of the time without a jacket over top—and it has yet to develop any holes or tears. The Fortris Spectra is designed to be even tougher.
All that said, the Fortis Spectra Hoody won’t earn you too many style points: it lacks the odor resistance of merino and is available in only a couple simple colors. Furthermore, $149 is a hefty price tag for a nylon baselayer and it can often be hard to find in stock in stores. However, impressive durability—and features like an under-the-helmet hood and chest zip—set the Fortis Spectra apart as a highly functional and long-lasting performance piece.
See the Men's NW Alpine Fortis Spectra Hoody
Materials: 100% polyester (body); 4% elastane (side panels)
Weight: 4.4 oz.
What we like: Absolutely fantastic all-around performance.
What we don’t: Technical design and fit isn’t for everyone.
Craft is a Swedish gear company with a cult-like following that is known for technical baselayers. In particular, they specialize in aerobic activities like cross-country skiing, biking, and running. The fit and styling clearly have performance in mind, and Craft may be overkill for casual use, but they make go-to baselayers for a lot of serious athletes.
The Active Extreme 2.0 isn’t your average thermal: it’s noticeably thin and lightweight and has a technical fit that is among the best on the list for those who really like to move (some baselayers have an athletic fit, but Craft really takes it to another level). As a result, this is decidedly not a casual layer. With high amounts of breathability (aided by ventilating mesh in high-sweat zones) and impressive warmth when you need it, Craft’s Active Extreme is ideal for high-output days.
See the Men's Craft Active Extreme 2.0 See the Women's Craft Active Extreme 2.0
Materials: 92% polyester, 8% spandex
Weight: 6.5 oz.
What we like: Simple yet functional.
What we don’t: Not super comfortable or a high performer.
In terms of bang for your buck, it’s hard to top REI baselayers. For $40, the Lightweight Crew offers most of the performance of the more expensive options above in a simple yet functional design. Additionally, REI honed things in even further with 8 percent spandex in the construction, which gives it a nice, stretchy feel. Paired with the matching bottoms, you can pick up a full long underwear set for $80 ($25 cheaper than just a merino top from Smartwool).
What are the downsides of the REI? We’ve found the lightweight model works well for mild resort skiing days, hiking, and casual use, but you may not be warm enough in frigid temperatures. And although the fabric is comfortably silky, it can’t compete with merino or even Patagonia’s Capilene in terms of softness and comfort (and it’s even more prone to holding in body odor). These issues aside, the REI Lightweight Crew is a good way to kit yourself out this winter on a budget.
See the Men's REI Lightweight Crew See the Women's REI Lightweight Crew
Materials: 51% merino, 49% polyester
Weight: 6.9 oz.
What we like: Amazing warmth in a tiny package; responsibly sourced wool.
What we don’t: Expensive; lacks durability.
Patagonia’s Capilene collection runs the gamut from thermal-weight baselayers to lightweight t-shirts and long-sleeve layers for hiking, and the midweight Capilene Air Hoody stands out as one of our favorites in the lineup. Known for leading the charge in their dedication to sustainable environmental practices, Patagonia outfitted the Capilene Air with recycled polyester (49 percent), and the net result is a responsibly made and truly innovative piece. With a balaclava-style hood, seamless construction, and a heat-trapping merino/polyester blend, the Capilene Air provides a massive amount of warmth in a relatively thin and lightweight package.
Although in theory the polyester make-up of the Capilene Air gives it a bump in durability, we developed multiple holes and runs on our hoody in a matter of weeks. Furthermore, it is noticeably permeable to wind, and the fabric tends to pill and act as catch-all for hair, fuzz, and more. For all these reasons, the Capilene Air makes a poor outer layer, unlike a baselayer like the NW Alpine Fortis Spectra above. But with great odor resistance, impressive wicking and drying properties, and one of the warmest, coziest hoods we know of, it makes a fantastic next-to-skin piece.
See the Men's Patagonia Capilene Air See the Women's Patagonia Capilene Air
Material: 100% merino wool
Weight: 8.9 oz.
What we like: Softer against the skin than Smartwool.
What we don’t: Slim fit and dense weave lags behind in breathability.
The Oasis Crewe from Icebreaker is as versatile as any baselayer on this list. It’s made from 100 percent merino wool, is super soft, and has a performance fit that works well for skiing and cool-weather hiking. And because of the clean styling and plethora of colorways and designs, you easily can wear it as a standalone piece.
If you’re considering the Oasis, it’s a head-to-head matchup with the Smartwool Merino 250 above. Both models are made from 100 percent merino and the prices are similar (the zip-neck version of the Oasis is $100). Both are comfortable, wick moisture well, and don’t trap odor like synthetics. But we give the slight edge to the Smartwool because the dense weave of the Icebreaker’s fabric doesn’t release hot air quite as efficiently. Despite having a lighter fabric weight (200 vs. 250g/m²), it can start to feel muggy when you’re working up a sweat. On the other hand, we do give it the edge in next-to-skin softness.
See the Men's Icebreaker Oasis See the Women's Icebreaker Oasis
Materials: 90% polyester, 10% elastane
Weight: 9.9 oz.
What we like: A fully featured heavyweight option.
What we don’t: Expensive and not very versatile.
Arc’teryx places a premium on high performance, which shows in their baselayer collection. No matter your tendencies for running hot or cold and regardless of the season, there is an Arc’teryx baselayer ideal for the job—including their midweight wool Satoro above and breathable Rho LT. And our list wouldn’t be complete without the expedition-weight Rho AR, a moisture-wicking, fleece-lined option for low-output activities, winter temperatures, or those who run particularly cold.
The Rho AR is marketed as a midlayer that can serve double-duty as a baselayer, but don’t expect the same level of breathability that you get from the thinner options here. What you can expect is a heavy dose of insulation and cozy loft at an impressively low weight—almost a half-pound less than the all-merino Woolx above. And unlike the Woolx, the Rho is performance-ready with a chest pocket, close fit, and zip neck for dumping heat. That said, we think $145 is a high price to pay for a not-so-versatile polyester layer, which pushes the Arc’teryx down our rankings.
See the Men's Arc'teryx Rho AR See the Women's Arc'teryx Rho AR
Material: 100% merino wool
Weight: 6.9 oz.
What we like: Great styling and super-soft hand feel.
What we don’t: Expensive and lacks durability.
We’ll start with the basics: the Ortovox 185 Merino long-sleeve crew is a standard merino baselayer. Much like the chart-topping Smartwool, it’s made with 100-percent wool, which means you get uncompromised odor resistance, great temperature regulation, and a cozy, soft touch. At 185 grams per square meter, it’s lighter than the Smartwool 250, meaning it’s more suitable for shoulder-season or high-output activities. That said, the thin fabric, paired with the fact that it’s not blended with a synthetic material, does make us concerned about the Ortovox’s durability (even Smartwool’s 150-weight shirt features a merino/nylon blend).
But here is where the Rock’N’Wool stands out: first, the Ortovox Wool Promise ensures that their product comes from ethical and certified sheep farms. And second, we just can’t get enough of the styling on the Rock’N’Wool—if you want a merino baselayer with some flair, the multi-colored designs really stand out in the conservative and largely bland baselayer market. For a versatile, breathable next-to-skin layer that can take you straight from skin track to après, the Ortovox 185 is an eye-catching choice.
See the Men's Ortovox 185 Rock'N'Wool See the Women's Ortovox 185 Rock'N'Wool
Materials: 89% merino, 11% nylon
Weight: 14.1 oz.
What we like: Maximum protection from the cold.
What we don’t: One-piece design is limited.
For maximum protection against the cold, a one-piece baselayer is hard to beat. Norway-based Norrøna’s offering in this category covers you from your head to just about your ankles with incredibly warm, comfortable, and breathable merino wool. The addition of polyamide (nylon) adds durability while also helping to wick moisture. Further, a long front zipper and drop bottom mean you can wear the One-Piece all day long.
The Wool One-Piece may be fun and useful for certain hardcore cold-weather adventurers, but it pretty clearly has limited appeal. The price tag is steep for a baselayer and most of the features are targeted to a very specific audience (including mountaineers, ice climbers, and the occasional backcountry skier). But we won’t fault you for being tempted by the idea of a functional and cozy adult onesie—and it’s hard to argue with the protection and warmth at a pretty darn light 14.1-ounce weight.
See the Men's Norrøna Wool One-Piece See the Women's Norrøna Wool One-Piece
Material: 81% merino, 12% nylon, 7% elastane
What we like: Ibex made some of the top baselayers on the market for years.
What we don’t: The new line is unproven and pricey.
It certainly feels good to have Ibex back. For years, this Vermont merino specialist churned out great products that were among the most stylish in the category. Then came financial troubles and an unfortunate fall from grace, but Ibex returned in 2019 with backing from New York. In the process, they trimmed their product line significantly but brought back the legendary Woolies. Here is what you get: a mostly merino baselayer that is soft, sleek, and even can be worn on its own. The nylon/elastane core helps with durability and stretch, and everything looks like the Ibex of old.
There are a couple of reasons why we don’t have the Woolies ranked higher. First, the 180g/m² crew version comes in at a steep $105, which is $5 more than the Smartwool 250g/m² Crew and $20 more than the 150g/m² lightweight version. Given Smartwool’s reputation and long track record, it’s tough to pay more for a relative newcomer (not to mention Ibex is all direct-to-consumer now, so you can’t try it on in-store). Second, we haven’t yet had the chance to put Ibex 2.0 gear through the wringer. Past iterations were strong on all fronts, but we’ll need a season or two of hard use out of our Woolies before it gets the full two thumbs up.
See the Men's Ibex Woolies Tech See the Women's Ibex Woolies Tech
Materials: 78% polyester, 22% Elasterell
What we like: Very warm and durable.
What we don’t: Snug fit isn’t as versatile.
Under Armour practically built their reputation on performance baselayers, so it shouldn’t come as a surprise that they have an impressive lineup for winter sports. To start, they offer a ton of warmth options—from ultra-lightweight, wicking gym shirts to true cold-weather pieces. We’ve included their warmest version here, the synthetic ColdGear Base 4.0, which has Under Armour’s classic snug fit and is a great match for frigid days and those that run cold.
In comparing the ColdGear Base 4.0 to another heavyweight on our list, the Woolx Glacier above, it’s a classic showdown of synthetic vs. merino wool. The Woolx is softer to the touch, doesn’t develop stink as quickly, and isn’t as prone to overheating. On the flip side, the Under Armour is more durable, wicks moisture well for its thick construction, and saves you $40. For us, the Woolx gets the edge with its nicer feel and less fitted cut that allows it to be worn as a standalone piece. But if you want a super warm synthetic baselayer with a performance fit, the ColdGear Base 4.0 is a fine option.
See the Men's Under Armour Base 4.0 See the Women's Under Armour Base 4.0
Material: 100% silk fabric
What we like: Cozy and great for layering.
What we don’t: Lacks the performance of merino or polyester.
Silk can’t compete with merino or polyester in terms of warmth, moisture wicking, and durability, but it’s not without its place in the baselayer world. Those who prize comfort above all else might choose silk for sleeping, around camp, and other low-output activities. Furthermore, silk is so thin that it can easily be worn underneath slim-fitting layers without creating extra bulk. And for only $50, L.L. Bean’s Silk Underwear is well-made and more durable than most silk options.
We don’t recommend wearing the Silk Underwear Crewneck for any sort of high-output activity—it simply does not breathe as well as merino or polyester. Moreover, if you want it to last, the shirt should always be layered with a mid or outer shell. In the end, silk falls short of the wool and polyester options above in nearly every performance category. But if you prioritize comfort above all else and like the feel of silk, the L.L. Bean Crewneck is worth a look.
See the Men's L.L. Bean Silk Crewneck See the Women's L.L. Bean Silk Crewneck
|Smartwool Merino 250 1/4-Zip||$105||100% merino wool||Midweight||10 oz.||250g/m²|
|Patagonia Capilene Midweight||$59||100% recycled polyester||Light/mid||6.2 oz.||147g/m²|
|Helly Hansen Lifa Stripe Crew||$40||100% polypropylene||Lightweight||5.1 oz.||125g/m²|
|Woolx Glacier LS Heavyweight||$120||100% merino wool||Heavyweight||17.6 oz.||400g/m²|
|Smartwool Merino 150 Crew||$85||87% merino wool, 13% nylon||Lightweight||6 oz.||150g/m²|
|REI Merino Midweight Half-Zip||$90||100% merino wool||Midweight||8.5 oz.||200g/m²|
|Arc’teryx Satoro AR Zip-Neck||$139||81% merino, 12% nylon, 7% elastane||Light/mid||6.9 oz.||180g/m²|
|NW Alpine Fortis Spectra Hoody||$149||90% nylon, 10% Spectra||Midweight||12 oz.||Unavail.|
|Craft Active Extreme Crewneck||$80||100% polyester (body); 4% elastane (side panels)||Lightweight||4.4 oz.||Unavail.|
|REI Co-op Lightweight Crew||$40||92% polyester, 8% spandex||Lightweight||6.5 oz.||Unavail|
|Patagonia Capilene Air Hoody||$149||51% merino, 49% polyester||Midweight||6.9 oz.||190g/m²|
|Icebreaker Oasis Crewe||$95||100% merino wool||Midweight||8.9 oz.||200g/m²|
|Arc'teryx Rho AR Zip-Neck||$145||90% polyester, 10% elastane||Heavyweight||9.9 oz.||Unavail.|
|Ortovox 185 Rock'N'Wool LS||$110||100% merino||Light/mid||6.9 oz.||185g/m²|
|Norrøna Wool One-Piece||$189||89% merino, 11% nylon||Midweight||14.1 oz.||170g/m²|
|Ibex Woolies Tech||$105||81% merino, 12% nylon, 7% elastane||Light/mid||Unavail.||180g/m²|
|Under Armour ColdGear Base 4.0||$80||78% polyester, 22% Elasterell||Heavyweight||Unavail.||Unavail.|
|L.L. Bean Silk Crewneck||$50||100% silk fabric||Lightweight||Unavail.||Unavail.|
- Baselayer Materials
- Important Strengths and Weaknesses
- Baselayer Categories: Insulation Weight
- Crew Neck vs. Quarter or Half Zips
- Key Baselayer Features
- What About Baselayer Bottoms?
- Layering Systems: Base, Mid, and Outer Layers
Merino wool, despite a higher cost than synthetics, is our recommended baselayer material for a number of reasons. It’s ultra soft and comfortable, has superior temperature regulation, and resists odor. Granted, merino wool baselayers are expensive and less durable than the polyester competition, amounting to roughly double the cost. Take good care of them, however, and you should be able to get at least a few seasons of extended use. Our top baselayer pick, the Smartwool Merino 250 ¼ Zip, is 100 percent merino. For more information about the pros and cons of the material, check out our article: Merino Wool: Is It Worth It?
For a cost-effective baselayer alternative, you can always turn to polyester. Led by Patagonia’s legendary Capilene line, polyester fabrics can keep up in terms of moisture wicking and the comfort difference isn’t that far off. The downside is stink prevention, which is an area of emphasis for many manufacturers. Thus far, odor-resistant polyesters still can’t compete with the natural benefits of merino but they are improving. In addition, polyester fabrics don’t regulate temperatures as well, so it’s more important to match the fabric weight with intended use and conditions (more on that below). Despite the downsides, polyester fabrics are what we recommend most often for resort skiers. At approximately half the price of a comparable merino option, the cost saving is too significant to overlook.
It’s not quite as simple as deciding between an all-merino or all-polyester baselayer. Some performance-oriented brands like Arc’teryx are experimenting with blends that aim to offer the comfort and performance of merino wool with the durability of polyester. One example is the Arc’teryx Satoro AR, which has a nylon core for durability wrapped in merino for next-to-skin comfort and odor resistance. The commonality of these types is that they are among the highest priced items in this market, so these blends are more about performance than cost savings.
Silk is one of the softest and most comfortable of the baselayer fabrics and packs an impressive amount of warmth into a lightweight, thin design. But as the demand for temperature-regulating baselayers rises, silk is largely going out of vogue. It just can’t keep up with merino or polyester in terms of moisture wicking and turns into a sweat lodge during high-output activities. Moreover, silk is far less durable than polyester and should always be worn under a mid or outer layer to protect from UV rays and abrasion. And finally, it does not resist odor like merino and should be hand-washed. We only include one silk option on our list for a reason, but it does have its advantages as a dedicated sleep shirt or extra layer in town.
The breathability of a baselayer is dependent on a number of factors, including the type and quality of the fabric, thickness, and openness of the weave. In general, lightweight merino wool will offer the best in terms of breathability, although some high-quality lightweight synthetics are close. This means that for high-exertion activities where you will be working up a sweat (think ski touring, cross-country skiing, biking, and climbing) it’s probably worth spending more to get a higher-performing baselayer like the merino Smartwool 150 or synthetic Patagonia Capilene. Craft’s Active Extreme baselayer is another very thin, very breathable synthetic option. Spending less, particularly on a thick baselayer, will yield less breathability. Whether or not that’s a deal-breaker is up to personal preference and your tendency to overheat.
Polyester: Very good
Silk: Not good
Merino wool excels at pulling moisture away from your skin, and less sweat build up means less stink build up. If you’re taking an extended backcountry trip and don’t want to carry multiple baselayers or rinse them each night, merino is the way to go. Some synthetics do fine for odor prevention, provided you aren’t working up a huge sweat. For example, we’ve hiked for extended periods in Patagonia’s Capilene in cool weather and have been impressed with its odor resistance. But nothing beats merino in keeping you dry and stink free.
Merino: Very good
Polyester: Not good
Silk: Not good
Here is where the tide changes: merino is super soft but prone to developing small holes over time that eventually hamper the performance of the product, whereas synthetics should last for multiple seasons. To put this in perspective, we usually get a season or two out of a standard lightweight merino baselayer, even from the top brands and by following their washing instructions (cold water and line dry). Admittedly, these shirts get a lot of use, but that’s still a very short lifespan. But with synthetics, one or two seasons would be on the short end of the spectrum and we would hope for more like three or four.
Some companies are blending wool and synthetics to increase the strength of the baselayer without compromising next-to-skin comfort, which is a good idea in our opinion. We haven’t noticed much of a drop in terms of comfort or performance, but merino/synthetic blends are a step up in durability. Even so, if we’re wearing a baselayer without anything overtop, we’ll always opt for a fully synthetic piece such as the NW Alpine Fortis Spectra.
Blends: Very good
Merino: Not good
Silk: Not good
Out of all the fabrics we’ve mentioned, merino has the best heat-trapping properties. In general, you get a better warmth-to-weight ratio with merino than with polyester, and it regulates temperature better too. The same shirt that keeps you warm in the winter will keep you cool when you’re sweating up the skin track in the shoulder seasons. Silk, too, is noticeably warm for its thin makeup, but its lack of breathability is a strong drawback. It’s also important to consider if you’ll be wearing your baselayer as an outer layer—while merino doesn’t do much to block wind, some polyester fabrics (such as Patagonia’s Capilene) are so tightly woven that they have the ability to resist light gusts. And keep in mind that warmth is directly related to the thickness of the material too, which we discuss in the Insulation Weight section below.
Blends: Very good
Logically, lightweight baselayers are the best breathers but do the least in keeping you warm. This is where merino wool shines—it does an admirable job of temperature regulation for the weight and thickness. However, the thinner the merino, the less durable it becomes. For this reason, most lightweight baselayers are made of polyester. These are ideal for early season skiing, bluebird days, and high-output activities such as cross-country skiing and cold-weather running. Resort skiers and winter climbers will likely opt for a warmer and cozier midweight baselayer.
For the widest variety of conditions, a midweight baselayer makes the most sense. It will provide the warmth you need yet still be breathable enough for physical exertion, especially when made with high-quality merino or polyester. Midweight baselayers are the most popular choice for downhill skiers: they’re plenty warm for the lift ride up but you are unlikely to overheat on the descent. They are less popular than lightweight baselayers for hiking or ski touring in moderate conditions as the extra warmth corresponds with a drop in the fabric’s ability to regulate temperatures (even merino can get too hot in warm temperatures). But in cool spring and fall conditions, a midweight baselayer can perform great as an outer layer and is the ideal next-to-skin layer for resort skiing on cold days.
Heavyweight baselayers are specialty items for cold temperatures or if you’ll be relatively sedentary. The extra thickness inhibits breathability and it’s easy to start sweating even on short walks. Keep in mind that you don’t need all of your insulation from a single article of clothing, and as a result, you can always add warmer layers on top of a light or midweight baselayer. But for winter mountaineering, extreme cold, or low-output activities around camp, a heavyweight baselayer can be the height of coziness. If you do go this route, we love the Woolx Glacier LS, which is a 400g/m² all-merino baselayer that still breathes decently well. Patagonia’s Thermal Weight Capilene can get swampy unless it’s very cold.
Nearly every baselayer on the market is made in a number of styles, including long-sleeve crew and half/quarter-length zippered shirts. Many folks opt for a crewneck style, but there are a number of reasons to think about a zippered shirt. One upside is the ability to adapt to changing weather conditions. Zip up for added warmth at the start of the climb, and unzip as you work up a sweat. And if you want to remove the shirt altogether, it’s nice not having to take off your helmet to do so. Furthermore, the extra coverage you get with the raised collar is a nice boost in warmth, and we’ve even found that quarter or half-zip long sleeves have a decent look for around town. The downside is the collars can flop around if you unzip the shirts while running, and having a zipper on your next-to-skin layer isn’t as comfortable as the cleaner crew style.
For optimal performance, baselayers need to have a snug fit. This helps the fabrics draw moisture away from your skin most efficiently. Some folks like wearing their baselayers for casual use, and that’s when a dedicated performance product like Craft Active Extreme is less useful. The shirt conforms to your body like a performance piece should, but it’s far too tight to wear anywhere else. A product like the REI Co-op Merino Midweight Half-Zip is on the opposite end of the spectrum, with a roomier fit that sacrifices a little in moisture wicking and breathability. But it’s a great choice for those that prefer a dual use baselayer/casual shirt. In the end, your decision is a personal one, and we recommend looking at fit based on intended use and preferences on style.
Baselayers can range from simple, featureless crew tops like the Icebreaker Oasis to hooded half-zips with a chest pocket (the NW Alpine Fortis Spectra, for example). If you know you’ll be layering a mid or outer layer over your baselayer, the simpler the better. However, those who wear their baselayer as an outer layer will appreciate zip pockets and thumb loops. And climbers and skiers will benefit from a tight hood or balaclava that fits under their helmet. Furthermore, some baselayers even have the capability of blocking sun rays (measured by the UPF rating). As usual, it will help to identify what you’ll be using your baselayer for before determining what features you need.
Most baselayers on this list have a matching bottom with the same construction and a similar or identical price. For organization sake, we list the tops here as they are more popular, but the bottoms are readily available and share the same pros and cons. In general though, maintaining a warm core will do much more for your entire body’s comfort than keeping your legs warm. But given that there’s no need to choose—and provided that almost nothing is cozier than a pair of long johns—we’re huge proponents of baselayer bottoms as well.
To get the most out of your technical clothing, it’s important think of everything as a system. Each piece relies on the layers around it to perform well. As an example, if you have a baselayer that wicks moisture well, but are wearing a fully rubber mid or outer layer, it won’t matter how nice of a merino fabric you have: you’ll still be wet and miserable. As such, take the time to put together mid and outer layers that are as high-performing as the baselayers listed above.
Baselayers have two primary functions: warmth and moisture wicking. Whether constructed with silk, wool, polyester, or a blend, a baselayer is made to retain your body’s heat while transporting moisture away from the skin. And these two features work together—keeping the body dry will in turn lead to more warmth. Baselayers are worn beneath a midlayer or shell during the winter months, or as an outer layer during the fall and spring for activities like hiking, biking, and climbing. The thickness and material of your baselayer will have big impacts on warmth and breathability, so make sure to keep this mind when making a purchase.
For high-output activities, such as hiking, backpacking and climbing, breathability is top priority. We recommend a fleece jacket or synthetic jacket for balancing warmth and ventilation. High performers include the Arc’teryx Atom LT and the R line of fleeces from Patagonia. If you only plan to grab your insulating layer during downtimes, such as hanging around camp after the sun goes down, consider a warm and super packable down jacket. Skiing is a similar story, and conditions will dictate the best midlayer for you. Options can range from a puffy down jacket to a light fleece.
Outer layers are the most specialized part of the system, and their complex designs can get quite pricey. A waterproof, breathable, and packable rain jacket is needed for activities like climbing and hiking/backpacking. Winter conditions are much harsher, so durability takes precedence for ski jackets. Their designs offer more pockets for storing gear or personal effects and a longer fit to protect you from snow sneaking through. There are also hardshell jackets that blur the lines, mixing the weight of a rain jacket with the performance (and extra cost) of a ski jacket.
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