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The Best Base Layers For 2023

Stay warm this winter with these top technical base layers

While most climbers obsess over the right clothing layering system for their winter adventures, they often fixate on their mid- and outer layers and ignore the importance of the right base layer. This thinking is understandable, as base layers, at first glance, don’t seem to have the eye-catching tech found in other garments. The truth, however, is that base layers have come a long way since the early (and stinky) synthetic offerings, and they now play a critical role in helping keep you warm, dry and comfortable. In a nutshell, the proper base layer helps your clothing system work as intended.

Here are our picks for the top base layers for 2023.

MEC T0 Base Layer Long Sleeve Top – From $31

BEST FOR HIGH-OUTPUT ACTIVITIES OR WARMER CONDITIONS
This lightweight base layer is perfect for warmer conditions or when you’re working hard and pumping out a lot of heat and perspiration. The top is constructed from a fast-wicking fabric blend of polyester and polypropylene, ensuring you stay dry and chill-free. MEC adds an antimicrobial treatment to prevent the funky odours sometimes associated with synthetic base layers.
Fabric Content: 53% polyester, 35% recycled polyester, 12% polypropylene

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MEC T3 Base Layer 1/4 Zip Long Sleeve Top – $56

BEST FOR COLD WEATHER CLIMBING
The T3 Base Layer provides the additional warmth required when mountaineering or belaying during ice-cragging sessions. The top is made with Power Stretch fleece fabric that provides excellent wicking and, thanks to the materials grid construction, efficiently traps warmth without adding excessive bulk. The addition of spandex offers stretch and allows for easy movement, while the generous front zip adds venting during periods of high exertion.
Fabric Content: 93% recycled polyester, 7% spandex

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MEC Merino T2 Base Layer Long Sleeve- From $70

BEST MIDWEIGHT LAYER THAT COMBINES THE BENEFITS OF MERINO WOOL AND SYNTHETICS
Consisting of a mid-weight blended fabric, the T2 Base Layer top is a solid choice for most winter activities. The fabric’s wool content helps keeps you comfortable over a wide range of temperatures, while the polyester improves moisture transfer, ensuring you stay dry and comfortable. Unwanted odours are minimized thanks to the wool’s antimicrobial properties.
Fabric Content: 46% merino wool, 35% recycled polyester, 19% polypropylene

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PATAGONIA CAPILENE AIR CREW – $170

BEST FOR CLIMBERS SEEKING AN INNOVATIVE MERINO-WOOL BLEND BASE LAYER
This sophisticated base layer blends merino wool with a soft polyester fibre creating a fast-drying base layer with excellent wicking and a high warmth-to-weight ratio. The Capilene Air Crew achieves this performance thanks to a unique airblasting technology that increases the yarn’s loft while reducing its weight. Patagonia also employs a 3D seamless construction that eliminates the bulk and chafing often associated with traditional seams.
Fabric Content: 51% merino wool, 49% recycled polyester

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Smartwool Merino 250 Base Layer 1/4 Zip Boxed – $105

BEST WARM MERINO WOOL BASE LAYER
Constructed from 100% merino wool, the 250 Base Layer is ideal for climbers seeking additional warmth in colder conditions. The fit has been updated for this season for greater comfort and ease-of-movement. The top features shoulder panel construction and flatlock seams to minimize chafing when wearing a pack. The addition of a 10” front zipper allows for easy temperature regulation during strenuous efforts.
Fabric Content: 100% merino wool

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Smartwool Intraknit Merino 200 Crew – $116

BEST LIGHTWEIGHT MERINO WOOL BASE LAYER
This lightweight crewneck top is ideal when you’re slogging uphill to the base of a route while wearing a big pack. The 100% merino wool construction provides warmth over a wide temperature range. Comfort is further enhanced by strategically placed open-weave panels that provide increased ventilation. Finally, the top remains relatively odour-free thanks to the wool fabric’s natural antimicrobial properties.
Fabric Content: 100% merino wool

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Icebreaker 260 Tech Long Sleeve Half Zip – $155

BEST MID-WEIGHT MERINO WOOL BASE LAYER WITH MAXIMUM RANGE OF MOVEMENT
This midweight form-fitting top delivers the required warmth for cold-weather climbing without sacrificing breathability. The top is constructed from 100% merino wool and features a half zip for ventilation and offset flatlock seams for greater comfort. Icebreaker has speced underarm gussets to ensure easy movement when swinging ice tools or reaching for that next hold. Finally, an extended back hem prevents unwanted drafts when bending over to adjust crampons or boots.
Fabric Content: 100% merino wool

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Icebreaker 200 ZoneKnit Long Sleeve Crewe Base Layer Top – $169

BEST MID-WEIGHT MERINO WOOL BASE LAYER HIGH-EXERTION ACTIVITIES
This mid-weight top from Icebreaker features strategically placed panels of merino mesh that deliver additional venting during strenuous activities. As with other Icebreaker base layers, the 200 ZoneKnit Long Sleeve Crewe is constructed from 100% merino wool, a material that offers warmth and wicking and avoids retaining odours thanks to its inherent antimicrobial qualities. Other exemplary features include offset flatlock seams for less chafing, an extended rear hem to stave off drafts, and thumb-loop wrist cuffs for additional hand warmth and reduced sleeve movement.
Fabric Content: 100% merino wool

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Here are some common FAQs (and answers) about base layers:

What’s the ideal weight for my base layers?

As with all seemingly simple questions, the answer is somewhat complicated. You first need to consider your activity level and personal metabolism. If you are involved in highly aerobic activities and you tend to run hot, you may want to lean towards lighter base layers. During these aerobic endeavours, you will generate plenty of heat and may not need the additional insulation offered by heavier fabrics. You will, however, appreciate the ability of lighter base layers to pull moisture from your skin, which will keep you drier and more comfortable. On the other hand, if you run cold and are less active (think extended winter belay sessions), you will probably prefer the extra warmth of heavier fabrics. And as you are less likely to generate as much perspiration, you will not be severely impacted by a reduction in moisture-wicking efficiency.

Should I get wool or synthetic base layers?

Let’s get this out of the way; merino wool is not scratchy like old-school wool sweaters, so don’t let the wool content scare you off. In fact, high-quality merino wool is incredibly soft, and proponents claim that it feels softer against the skin than some synthetics. Wool has a very broad temperature comfort zone, keeps you warm when wet, and does a surprisingly good job of pulling moisture away from your skin to keep you dry. Wool also has natural anti-microbial properties resulting in garments that won’t stink after a few hours of use. Finally, wool is 100% sustainable and biodegradable.

Synthetics, on the other hand, will also keep you warm when wet, tend to be lighter, are more durable, offer similar (if not better) wicking and dry faster. They can also be treated to avoid the dreaded synthetic base-layer stench that many synthetic next-to-skin garments seem to develop after some use.

Some companies today are starting to blend merino wool with synthetic fibres to produce base layers with the best properties of both materials. Consider your needs and budget and get what appeals to you. You’re not likely to be disappointed.

How should I wash my base layers?

You can clean synthetic and merino wool base layers in the washing machine. Simply use an appropriately mild detergent, choose a gentle cycle with cool to warm water, and you’re done. Drying is similarly straightforward; hang dry or put in the dryer at a low heat setting. And if you are ever in doubt, just check the garment’s care label.