It is through no fault of my own that I keep reaching for the Alpha IS: this is one damn amazing piece of outerwear, and one of the most versatile jackets I’ve ever used.
I honestly don’t know where to begin describing the Alpha IS so let’s just get down to the details. The main insulation is Arc’teryx’s own ThermaTek, wrapped in a two-layer Gore-Tex outer, with an additional layer of highly breathable Coreloft Continuous 65 added in for good measure.
Unless you’re familiar with Arc’teryx’s nomenclature and proprietary fabrics, that might not make much sense so let’s dissect it a bit.
ThermaTek is a continuous filament insulation, extremely hydrophobic thanks to a DWR treatment that is applied to each strand. It compresses very well, and retains excellent loft even when wet. At about 92g/m it is very warm, and is the main insulation in my favourite belay jacket of all time, the now discontinued Solo Hoody (review here).
Gore-Tex is pretty self-explanatory, and the two-layer version used in the Alpha IS is arguably even more breathable than the typical three-layer fabrics thanks to the absent inner backing layer. Instead, the ThermaTek insulation is actually laminated to the Gore-Tex for a more supple, breathable and packable jacket.
An evolution of the Coreloft insulation used in Arc’teryx’s well-known Atom line, Coreloft Continuous is, like the name implies, a continuous strand insulation. Thanks to it being strands of insulation rather than loose fibres, it can be encased in much ‘looser’ inner and outer fabrics, resulting in a much more breathable garment. Arc’teryx also use this in their Proton line of active-insulated mid/outer layers (Proton AR review here).
So, how does all this high-tech, laminated, continuous, DWR-treated, tech actually work?
Somewhat surprisingly, actually, really, really well. The Alpha IS is equally adept as a belay parka, an approach piece or a climbing layer. It really is all that and then some, and the more I wear it the more useful it turns out to be.
As some examples, I’ve used it ice climbing over just an ultralight base layer at -5c and was perfectly warm and windproof and breathable enough that I didn’t even sweat. At the same time, you can bring it on those -15c days and throw it on as a belay parka and it keeps the snow and wind out: the deep hem keeps your butt warm while the hood swallows your helmet. Or I’ll just throw it on over a typical mid-weight base layer and use it on the approach. It just seems to work in every scenario I use it in, and as a result it bring it more and more often and it just keeps performing beyond expectations. The versatility is rather baffling.
Fit-wise, and given the myriad of uses, it’s a little bit of everything. The hem is deep and easily covers my butt, and while the torso is a bit loose to accommodate layers, it isn’t so big as to feel too large when worn over just a light shirt. The sleeves are long and roomy, while the hood is the superb StormHood, which is the best helmet-friendly hood design out there, period.
Further highlighting the Alpha IS’s multi-use nature, the main zip is a waterproof Vislon with dual sliders so you can open it up from the bottom while belaying. There’s even a hem snap to keep the jacket tight around your butt while the zipper is open — a small but highly useful feature we just don’t see enough, even on dedicated belay parkas.
There are two fleece-lined hand pockets, positioned up high and above a harness or waist belt line. The zippers on these are also WaterTight, with an additional protective flap, so there’s little chance of snow or ice (or water, for that matter) getting in. There’s also a sizeable outside chest pocket, also with a WaterTight zip, that seems waterproof from the inside and out — so if you stick a phone in there, it won’t get soaked from precipitation or perspiration.
Inside, there’s a large mesh drop pocket on the right side for gloves, water bottle, etc. It has a built-in loop for attaching the included stuff sack. Unlike some other drop pockets I’ve seen, this one is high enough so as not to obstruct whatever gear you might have on your harness: a typically thorough, thought-through, Arc’teryx design.
Weighing in at a 600 grams for a Men’s Medium, the Alpha IS weighs considerably less than the equivalent in Gore-Tex (490 grams) and insulated jackets would (508 grams for a Solo Hoody, and 425 grams for a Proton AR). However, it also costs an eye-watering $1200 Canadian but, given just how multi-talented it is, and taking into account that, say, an Alpha SV is $900 CAD, the Alpha IS actually seems to represent very good value (no, I can’t quite believe I just wrote that, either).
Keeping all that in mind, then, the Alpha IS an excellent jacket. It defies expectations and blurs the lines between what a multi-functional jacket can be. I’ve been seriously impressed with it, and as I mentioned before, find myself bringing it along more often than I ever thought I would. It truly is a climbing shell and belay jacket and a half-dozen other layers all combined into one. Highly recommended, but it does cost over a thousand dollars, and I still haven’t quite made my peace with that.