| Awards |  Best Cold Weather Performance |  Best Merino Women's Long Underwear | Best Synthetic Women's Long Underwear |  Best Value for Merino Bottoms | Best Value for Synthetic Bottoms |
|---|---|---|---|---|---|
| Price | Check Price at REI Compare at 2 sellers | $150 List Check Price at REI | Check Price at Backcountry Compare at 2 sellers | $80 List $79.99 at Amazon | $55 List $54.95 at REI |
Overall Score  |
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| Star Rating | |||||
| Bottom Line | In addition to warmth and breathability, these bottoms feature articulated patterning for excellent range of motion | These lightweight bottoms offer top-notch breathability and unique thermoregulation | While not recommended as a stand-alone piece due to the see-through polyester fabric, we love the superior breathability that helps keep us warm and dry | These bottoms offer a ton of warmth and substantial comfort at a more affordable price | These lightweight tights feature a soft and stretchy fabric that is easy to layer and maintains substantial warmth when dry |
| Rating Categories | Smartwool Intraknit... | Icebreaker 200 Zone... | Patagonia Capilene... | Minus33 Franconia M... | REI Co-op Midweight... |
| Warmth (25%) | |||||
| Breathability (20%) | |||||
| Comfort and Fit (20%) | |||||
| Durability (15%) | |||||
| Drying Speed (10%) | |||||
| Layering Ability (10%) | |||||
| Specs | Smartwool Intraknit... | Icebreaker 200 Zone... | Patagonia Capilene... | Minus33 Franconia M... | REI Co-op Midweight... |
| Measured Weight (Size Small) | 8.32 oz | 5.63 oz | 4.90 oz | 7.52 oz | 6.40 oz |
| Material | 52% Merino wool, 45% polyester, 2% elastane, 1% polyamide | 100% Merino wool | 92% recycled polyester, 8% spandex | 100% Merino wool | 92% recycled polyester, 8% spandex |
| Insulation Weight Class | Midweight | Lightweight | Midweight | Midwewight | Midweight |
| Smelly Over Time? | No | No | Yes | No | Yes |
| Odor Control Fabric | Merino yes, polyester no | Naturally odor resistant | HeiQ Fresh | Naturally odor resistant | No |
| Cuts Avaliable | Full-length | Full-length | Full-length, boot-length | Full-length | Full-length |
| Listed Fabric Weight (g/m²) | Not disclosed | 200 g/m² | 129 g/m² | 235 g/m² | Not disclosed |
The Intraknit Thermal stands apart from the other long underwear bottoms in this review thanks to a modern design with gender-specific body mapping for enhanced warmth and ventilation. Unlike other midweight bottoms that provide warmth but retain moisture during activity, these bottoms keep you warm by offloading sweat.
SmartWool really nailed a niche category by adding articulated patterning and ventilation panels to a midweight design. The intelligent Intraknit technology efficiently regulates body temperature by offloading excess moisture to trap and maintain the body heat generated during rigorous activity. Unlike most mid- and heavyweight options in this review, which retain moisture, these tights are highly functional at thermoregulation.
During our testing period, we hit the trails, skin track, and dry roads in temperatures ranging from 15-55 degrees Fahrenheit. We were impressed with the warmth these bottoms offered without causing us to feel overheated or cold from sweat. When temperatures dropped below 10 degrees (depending on humidity), we would have been more comfortable with another layer over the top. Still, we were surprised with how well the Intraknit can retain body heat. Likewise, the same ventilation panels successfully released warmth in temperatures above 55 degrees. These are a great option if you're looking for a cold-weather long underwear bottom that offers a ton of warmth without sacrificing moisture management.
While we were initially skeptical, the Intraknit repeatedly proved us wrong. To measure the overall breathability of these bottoms, we hit the trails, sprinted on dry roads, and got moving on the skin track. Throughout each activity, with varying weather patterns, these bottoms successfully wicked moisture away from the body and released it through the fabric.
These are some of the thickest bottoms we tested, but the ventilation panels help set them apart from the rest, amplifying cold weather insulation and managing moisture. If we have any complaints, it is the thicker waistband. Although admittedly, it is hard to complain about this feature because it provides such excellent structure and holds these bottoms in place. But if sweat is going to pool anywhere, it's here. Overall, the breathability of the ventilation panels improves the design, making these bottoms perfect for high-output activities like backcountry skiing and trail running.
While we absolutely love the fit, especially the mid-rise 2" waistband that hugs the curves and provides some structure to the Merino sport yarn fabric, we had to dock these tights a few points for minimized comfort. The Merino sport yarn and polyester blended material add a ton of value to these tights but, unfortunately, sacrifices that next-to-skin Merino wool comfort — we found the fabric to be itchy at times.
The fit is a different story. The Intraknit truly offers extraordinary fit due to its integrated body mapping technology with minimal use of flatlock seams. The full-length fit is true to size, and perhaps our only complaint is that the articulated knees sit just above our actual knee when wearing a size small on our 5'6" frame. We love the increased range of motion we can achieve with this thoughtful fit, in addition to the ventilation panels that increase comfort by keeping us dry; we just wish we didn't have to give up that super soft next-to-skin comfort we've grown accustomed to with Merino wool.
We're happy to report that we've experienced no durability issues with these tights, even after taking an unexpected digger while running fast through some technical terrain in the desert. SmartWool really increased the durability of the Merino sport yarn by adding polyester, which helps give some structure to these wool tights.
If you want to extend the life of these high-quality long underwear bottoms, we recommend following the care instructions by washing them in a machine on a gentle cycle and laying them flat to dry. This will prevent any damage from the heat of the dryer or unwanted stretch from drying on a hanger.
It was important to our testers to consider the drying speed of each layer while simulating what it would be like to wash and dry the layer during an extended trip in the backcountry. As expected, due to the thicker, heavier material, the Intraknit also required more time to dry at 65 minutes.
We found that the drying speed increased by more than double when the layer could utilize body heat generated during high output activity such as runs and skinning uphill. In those circumstances, these bottoms dried as quickly as 25 minutes on the body. It's not a stellar performance here, but considering these weigh 8.32 ounces and offer stellar warmth and thermoregulation, it's not too bad, either.
Unfortunately, we found these tights to be a little tricky to layer due to a very slim fit. The Merino/polyester blended fabric can get a little grabby with things like ski bibs or pants unless those layers offer a smooth fabric interface. This resulted in some friction that was noticed during our uphill skin track testing drills.
The thicker fabric of the bottoms and the wide 2" waistband can also reduce the space you might normally be accustomed to inside your ski bibs. That said, we love that the Intraknit can easily be worn as a stand-alone piece, in addition to easy layering with rain and puffy pants that feature a smooth fabric to interface with.
These high-performing bottoms are worth every penny. For those looking for a versatile cold-weather bottom that amplifies thermoregulation and breathability through strategically placed ventilation panels, whether worn on their own or layered within a system, the Intraknit puts a modern twist on midweight insulation.
