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The Best Base Layers for Backpackers

Your warmth strategy starts with your next-to-skin layer. Pick the right one.

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Smartwool Merino 250 Asym Bottom

Smartwool Merino 250  Asym Baselayer Bottom best base layers
Smartwool Merino 250 Asym BottomCourtesy

There’s no such thing as bad weather when you have good layers—at least, that’s how these midweight, women’s-only merino tights made us feel on the coldest days. Under snow pants, they kept us toasty and dry on subzero ski tours across the Rockies in Colorado and Wyoming. The warmth derives as much from the cut as the material. Testers praised the Asym’s tailoring, which reaches up to the belly button in front, while a higher rise in back prevented gaps when we bent over. The merino also kept up with the sweat we produced on sunny days up to 40°F, but these tights’ sweet spot is low- to moderate-intensity activity in cold weather.

The Asym adds all-day comfort with a snug, 3-inch waistband that never dug into our sides: “I never got that stuffed-sausage feeling,” one tester says. While not as flexy as elastane blends, merino’s slight natural stretch proved sufficient.

“These tights aren’t thin, but they’re stretchy enough to skin up steep terrain with zero mobility issues,” reports one Colorado tester.

$100; 7 oz; Buy Smartwool Merino 250 Asym Bottom Now

Helly Hansen Lifa Merino Seamless ½ Zip and Pants

Helly Hanse Lifa Merino Seamless Baselayer best base layers
Helly Hansen Lifa Merino Seamless ½ Zip and PantsCourtesy

Pair wool’s insulating power with synthetic’s wicking, and you get a garment that cashes in on both. Hybrids aren’t new, of course, but Helly claims the Lifa Merino’s unique polypropylene-elastane blend (woven together with merino) outperforms other synthetics as a hydrophobic fiber. Our testers agree: The set kept us comfy on humid ascents of Washington’s Mt. Shuksan and 50°F days in Missouri’s Mark Twain National Forest. Still, it’s warm enough for active use into the teens when paired with a light midlayer. Helly’s new “seamless” construction—the body, arms, and pants are made of single pieces of fabric rather than panels stitched together, which reduces the number of connection points—eases chafing and enhances stretch. Ding: Some testers reported the knees bagged out after a few days.

The pants’ smooth waistband never bunched or pinched under a hipbelt. Note: The slim cut helps pull sweat away from the skin, but those with larger body types will want to size up.

“Over seven straight days of wear, these resisted odor so well I easily could have kept on using them,” one guide says.

$110; 8 oz; Buy Helly Hansen Lifa Merino Seamless ½ Zip and Pants Now

The North Face Wool Baselayer Tight

The North Face Wool Baselayer Tight best base layers
The North Face Wool Baselayer TightCourtesy

The best backcountry skiing apparel hits the sweet spot of fit and moisture management, two areas these thin tights have dialed. They’re designed for skiing, with an above-boot cut that never rides up (thanks to a bonded finish at the cuffs) and a 1.5-inch-thick waistband that layers flat under shell pants, pack hipbelts, and harnesses. And though they’re 100-percent merino, they were light enough to dry quickly when we went from broiling climbs to high-altitude snack breaks. Caveat: They’re not the warmest, so pick a heavier pair if you run cold, your route has a lot of transitions, or you spend a lot of time at the belay station.

The Wool Baselayer Tight moves well for full merino and never hindered us on ski tours around Jackson Hole, Wyoming. Bonus: They were the most stink-resistant out of all the baselayers we tested.

“We started our climb to New Zealand’s Mueller Hut in blindingly sunny conditions, but by the time we reached the ridge, we were in biting winds and getting pegged with graupel,” our tester says. “These tights kept me comfortable at both ends of that spectrum and everywhere in between.”

$99; 6 oz; Buy The North Face Wool Baselayer Tight Now

Under Armour UA Base 2.0 Hoodie and ¾ Legging

Under Armour UA Base 2.0 Hoodie and  ¾ Legging best base layers
Under Armour UA Base 2.0 Hoodie and ¾ LeggingCourtesy

Sometimes, it’s the things you don’t notice that make a baselayer shine. That’s the case with this set. From fat bike rides to backcountry ski tours, we never had to worry about restricted movement, soaking in sweat, or shivering when temps dipped. The Base 2.0’s polyester-elastane blend (the reason for the wallet-friendly price) is gridded to trap heat and wick moisture, which kept us comfortable from 0°F to 40°F when paired with a shell. Tradeoff: Although it’s treated with an anti-stink agent, the material got pretty funky aftera few wears.

The separate neck gaiter and hood sealed out gusts and slid easily under a helmet. The pants work nicely for skiing, too, thanks to a bunch-free knicker cut and a yoga-style waistband. Gripes: The fabric has a “crunchy” feel and Under Armour’s usual tight fit, which left some testers feeling constricted and exposed.

“I had to wait for my ski tour group in an open basin with gusty winds and expected to go from burning hot to freezing cold, but these bottoms kept me cozy,” says a Colorado tester. “I cooled down, but the tights didn’t trap sweat against my legs.”

Hoodie: $49; 9.3 oz.; Buy Now; Pants: $33; 6 oz; Buy Now

Terramar The Beast Half-Zip Baselayer

Terramar The Beast Half-Zip best base layers
Terramar The Beast Half-Zip BaselayerCourtesy

The thermoregulating Beast sometimes seemed smarter than us­. When we were cold, its polyester fibers contracted, mechanically tightening the weave to retain extra heat; when we were steaming, they loosened to let air in and sweat vapor out. The secret? ClimaSense Carbon, a nanoparticle treatment on the fabric that responds to your temperature and sweat levels. The company won’t say how it works, but we felt the effects on daylong Alaska ski tours with 40°F temp swings. The Beast’s sweet spot is active use around 15°F, but its temperature control and good-for-its-weight dry times also kept us in the comfort zone while skinning uphill in warmer weather.

Mesh inlays in the pits and a zipper that dips to the sternum vent heat. Drawbacks: Testers with long torsos found the cut too short, exposing their lower backs when they bent over, and the Beast doesn’t come in a women’s version.

“Over days skinning across a glacier with a pack, I felt sweaty when the temps rose to the 20s or higher,” reports an Alaska tester. “But the top dried in 30 minutes as I set up camp.”

$65; 13 oz; Buy Terramar The Beast Half-Zip Baselayer Now

Cabela’s Merino Baselayer Top and Bottoms

Cabela’s Merino Baselayer  Top and Bottoms best base layers
Cabela’s Merino Baselayer Top and BottomsCourtesy

Merino performance doesn’t come cheap—at least, not usually. Yet, Cabela’s kept this set down at synthetic prices without sacrificing any of wool’s essential perks. (The company credits its negotiating skills with suppliers and ability to place large orders for the discount.) We bundled into it for ski tours and Colorado resort days that dipped as cold as a -30°F with windchill (layered under a puffy and insulated pants) and wore the top on its own into the 30s. And though we sometimes worked up a sweat, the layers never felt swampy; they’re fairly thin, and the merino pulls moisture away from the skin even when the fabric itself is not totally dry. But check fit first: A tall, thin tester reported the top to be tight in the shoulders and arms.

You get a simple, no-frills design, although the drop-tail hem on the top is a nice touch. Bummer: The set isn’t available in women’s sizes.

“Given their price, I thought they would lose their shape quickly,” reports a Colorado ski patroller. “But the neck and sleeves never stretched out.”

Top: $50, 8 oz.; Buy Now; Bottom: $50, 8 oz.; Buy Now

How to Pack for Backcountry Skiing

Get to know the winter safety gear you need in your pack.