The Rho AR
by Arc'teryx is a synthetic, midweight long underwear top that can also double as a mid-layer. It is very warm, and has a cozy and soft interior. It also features an excellent fit without restricting mobility. However, it didn't breathe as well as the other models in this review and has a slow drying speed after becoming saturated. There are several things we like about this model, but its $145 price tag isn't one of them.
Ross Robinson in the Rho AR from Arc'teryx, heading up the iconic El Misti shield volcano in Arequipa, Peru. The below-freezing temperatures required a warm top like this one, but we were somewhat disappointed in its breathability when we began to sweat.
The Rho AR
looks warm, and it certainly is. It scored the highest of all models in this category. It is also one of the heavier products we reviewed, coming in at 10 oz. With a very snug, but comfortable, fit, it is able to trap heat very well. The sleeves and torso are extra long to allow for a full range of movement without exposing wrists and belly-buttons to the air. We would have appreciated a strip of material behind the zipper to block air from coming through this extra porous zone though, as seen on the Mountain Hardwear Microchill 2.0
When you need a warm top for daybreak summit pushes, the Rho AR is ready for the wake-up call.
When things get too hot, the 9 ½ inch zipper can quickly release excess heat. However, even with this feature, we found it easy to overheat when engaging in moderate activity. When hiking El Misti volcano in southern Peru, we worked up a sweat in this base layer underneath a down jacket before the sun came up at 18,000 feet above sea level, despite temperatures below freezing. When worn as a first layer, this top performs best in no to low activity, even in cold conditions. For a more versatile but still warm base layer, the SmartWool Merino 250
is an excellent choice.
By comparison, this Arc'teryx model is one of the least breathable tops we reviewed. Being so warm, it was easy to work up a sweat in this product. Instead of immediately wicking this moisture away, it often condensed on the inner jersey fabric, where it stayed until it could be transmitted to the external environment. When this happened high up on the side of a volcano, the cold, condensed sweat chilled us whenever we stopped for a break. Although it didn't take very long for this moisture to move away from our body, it was 2-3 minutes longer than we wanted in cold conditions.
While it didn't score very high in this metric, its score is relative the other very breathable products in our selection. The Rho AR does provide breathability superior to most hard and softshells, rain jackets, and wind shirts.
If you plan on producing some sweat, we recommend more breathable products, like the SmartWool Merino 250
or the Helly Hansen Lifa Stripe Crew
Comfort and Fit
The Rho AR
is one of the most comfortable base layers. The soft jersey inner fabric felt great against our skin. Its super stretchy material fit snugly along the contours of our torsos, providing one of the best fits of all. This top also stayed in place very well, so that we weren't constantly adjusting it, as we were with the Icebreaker Oasis
. The flatlock seams maintain a low profile and are placed away from areas typically high in chafing. With substantial side and underarm gussets, this product has great mobility as well. The only product we found more comfortable was the SmartWool Merino 250
The Arc'teryx model was the only one to feature a pocket, which was useful for small items like a key or some cash for a post-summit celebratory beverage.
Coming in tenth place in our drying speed test, the Arc'teryx model dried 58% slower than the fastest product, the Lifa Stripe Crew
. However, there was a silver lining. Like the merino wool products, the synthetic fabric of the Rho AR
was difficult to saturate with water, as it resisted soaking up the water. The Mountain Hardwear Microchill 2.0
was similar in this fashion too. Also like the Microchill, the top upper ¾ of this model dried out quickly, as all the water drained to the bottom ¼, where it took a very long time to evaporate. If we had been in the backcountry when this happened, we would simply wring out the bottom quarter of the shirt to speed up the drying process. But, in order to keep the test standard and fair, we didn't.
If you find yourself soaking wet away from shelter in this Arc'teryx product, we recommend wringing out the lower portion of the shirt, as the water will gravitate toward this spot more than in other base layers.
The Rho AR
stood out as the best above the rest in layering ability. We were able to put this top over and under anything we would consider actually using as a layering system in the outdoors. Over t-shirts and even thicker base layers, such as the Minus33 Isolation Midweight Wool
, and under jackets and mid-layers, this long underwear product performed like a champ. Considering its low breathability, our main reviewer tended to wear this model primarily as a mid-layer.
When skiing in the Sierras, we liked the comfy, warm, and flexible combination of the SmartWool as a base layer and Arc'teryx model serving as a mid-layer, with a hardshell overtop.
This Arc'teryx model is one of the most durable tops featured in this review, along with The North Face Warm
and Mountain Hardwear Microchill 2.0
. Its fabric is strong, and the triple and quadruple-stitched seams appear ready to endure a heavy beating. The fabric isn't snag-proof, though, which showed in a few spots after three months of heavy use. Most annoyingly, this product could be confused for a pharmaceutical company with the amount of pilling going on all over its surface. This occurred after just a few uses and stayed around ever since.
The pilling of this model turned a once great-looking top into somewhat of an eye-sore.
Using a razor, you can remove the unaesthetic pilling from this shirt. However, for a shirt that costs $145, we wish this wasn't necessary.
The Rho AR
is best used as a first layer in cold and frigid weather during periods of limited physical activity. We prefer not to break into a sweat when in cold conditions with this model. It also serves as an excellent second layer over performance t-shirts and other base layers.
The Rho AR is built for the cold, but its inability to breathe very well made it only appropriate to lower-level activity.
This contender was the most expensive model we selected for this review, costing $145. While it performed very strongly in multiple categories, we found it hard to justify spending so much on a product that didn't provide all-around performance, nor truly specialize in any use. The Editors' Choice SmartWool Merino 250
performs better overall, and costs a full $45 less. For only $60, you can take home the Best Buy winner, The North Face Warm
, which scores well across the board.
The Arc'teryx Rho AR
had potential for winning a Top Pick award. It's very warm, ultra-comfy, and durable. We were also impressed with its versatility, easily doubling as a mid-layer when necessary. However, its low score in breathability took it out of the running, as this is a very important characteristic for quality base layers. We still enjoyed wearing this model, but found its extreme price tag just as severe of a drawback as its below-average breathability and drying speed.