Active breathable insulation is nothing new by now — every major brand has at least a couple of these pieces in their clothing line-up, most utilizing some form of Polartec’s Alpha insulation. Arc’teryx often have proprietary fabrics and insulation fills, and the Coreloft Continuous used in the Proton AR is no different.
An evolution of the venerable Coreloft insulation, most commonly seen in the Atom series, the Continuous version is just like it sounds: the fibres have been woven into long strands that are much easier to contain within a shell fabric (i.e. the bits and pieces of insulation don’t try to escape through the fabric weave, think of how down always somehow finding a way out through stitches and seams). This allows for the use of much more air permeable shell and liner fabrics, resulting in a much more breathable garment.
The Proton AR uses Coreloft Continuous in two weights, 90g/m in the torso and 65g/m in the arms and hood. The outer is a light but wind-resistant Fortius Air 40. This results in a very warm jacket, albeit one with excellent breathability and very good wind resistance.
Thanks to the relatively heavy-weight 90g/m insulation, the Proton AR is quite warm and I’ve used it over just a base-layer down to -20C, both during approaches and on climbs. Similarly, thanks to the excellent breathability, I don’t hesitate to throw it on during a chilly summer evening around the campfire as I know I won’t sweat underneath it. It is, however, too warm for me to wear as an active piece when it’s warmer than -10C or so: I simply produce so much heat that even the Proton AR can’t dump it fast enough.
Wind resistance is good enough that it can be used as a stand-alone layer, but the outer is a smooth weave that slides just as easily under other jackets. It is one of the more versatile breathable-insulated pieces that I’ve used, and I find myself bringing it along on most outings, be it ice climbing in the middle of winter or a desert camping trip in the height of summer.
Fit is typical Arc’teryx-active focused, with long sleeves, a deep hem and helmet-friendly hood. The cut is trim, and I generally wear it over just a base layer, though it will accommodate a light mid-layer underneath if required.
The stretchy cuffs seal comfortably around my wrists, and the sleeves don’t ride up too much during acrobatic moves or long overhead reaches. The hood isn’t Arc’teryx’s excellent StormHood but it still goes over a helmet without restricting movement, and it’ll comfortably cinch down over just a toque.
There are two chest pockets (with the cutest tiny zippers!) which I absolutely love to see on a jacket, as well as two insulated, also zippered, hand pockets. Normally I gripe about hand pockets on climbing jackets but as this is such a versatile piece and I wear it everywhere, I’ll concede that the hand pockets are useful in less vertically-inclined endeavours.
I’ve had the Proton AR for over a year now — I received a pre-production sample back in January 2016 — and it’s been everywhere with me, and has come along on almost every outing. So far I’ve managed to put a hole into the left sleeve, and a few light tears into the hem. Even the DWR has held up well, and light rain still beads up on the surface.
There are so many breathable insulation options available that it’s hard to keep track of them all. At 425-grams in a Men’s Medium, the Proton AR is not the lightest, and neither is it the most breathable, or the most wind-resistant. But it is a solid all-around jacket that’s great at dumping heat when you’re working hard in very cold conditions. I also love the design (those two chest pockets!) and the fit is — like other Arc’teryx pieces — pretty much perfect.
Recommended, especially for extended winter climbing, or if you tend to run cold, or just want a versatile jacket to use year-round.