Back in 2012, Polartec unveiled听Alpha, a breathable, moisture-wicking synthetic midlayer insulation that they had developed for the U.S. Special Forces before releasing it to consumers. This insulation fill听completely changed how I and many other people dressed in the winter.听Since it vented and didn鈥檛 soak up water, the听midlayer听could be worn during听skins, runs, or bike rides without turning into听a soggy听mess. Today, Alpha is still around, but many other brands have also tried to develop the kind of breathable听syntehtic听insulation that made the original so special.听To see how they stacked up against each other, I put today's most popular midlayers to the test.
The Test: I spent all of January听wearing each of the midlayers while skiing (both inbounds and in the backcountry), running, and doing yard work. I used them all in varying temperatures and conditions, from blustery and cold 18 degree days听to听bluebird听days听where temperatures peaked in the 50s.听
OR Deviator Hoody听($185)
Insulation Technology: The uses Polartec Alpha. Alpha was听a big advancement because unlike pervious insulations听that needed baffles, or tightly-woven fabrics,听to keep them in place (which cut down on breathability), it was made into a free-standing sheet and could be sandwiched between more open and breathable听fabrics on the inside and outside of a jacket. Alpha is hydrophobic, so it moves water away from your body, and it also packs down well.
The Results: This was the most breathable jacket in the test because OR matched Alpha on the chest with the super-breathable Polartec Power Grid fleece on the arms, hood, and back of the jacket. I didn鈥檛 start to really sweat until a mile into a 51-degree run with it zipped part way up.
Best For: The mix of Polartec fabrics made this a great layer for winter running, but you might want something thicker for skiing.
Patagonia听Nano听Air Light听Hoody听($250)
Insulation Technology:听FullRange听Insulation听was developed by听Toray听Mills, a large听Japanese fabric developer,听and, like Alpha, is constructed so that it independently holds together and can be sandwiched between two breathable fabrics. It鈥檚听hydrophobic but also stretchy, which is important because Patagonia harnessed that feature to make the entire听Nano听Air Light听stretchy听(a feature I really love).听
The Results:听This jacket is not as warm as the regular听Nano听Air,听but it's more breathable. I found that it听had just enough insulation to keep me warm down to the mid twenties, but also kept me from getting too sweaty when I was working hard while in the yard听or skinning. Warning: the wind cuts right through it, so I needed a shell on top when听it was blustery.听
Best For:听This is a great layer for really high output activities in the high alpine. Or, for us mortals, it's great for听backcountry skiing on calm bluebird days.
Rab Alpha Direct Jacket ($265)
The Technology: As the name implies, this jacket uses Alpha Direct, which is Alpha insulation that doesn't need an inner lining when placed in a jacket. Put another way: if you look at the inside of this jacket, you鈥檙e seeing the guts of the Alpha insulation instead of the breathable fabric you'd normally see. Alpha Direct is more durable than regular Alpha, which is why听it doesn鈥檛 need an inner lining to听protect it from abrasion. 听
The Results: is thicker than the Deviator鈥擨 got hot on the skin track as well as on a resort day during a week when the temperatures climbed into the upper 30s and low 40s. However, I was impressed with how quickly it moved moisture. After soaking the Alpha Direct in sweat on a 3,000 foot backcountry ski climb, it was dry in under 15 minutes. 听听
Best For: This jacket is perfect for people who live in cold environments and run hot. It insulates well, but won鈥檛 wet out and freeze.
Arc鈥檛eryx Proton LT Hoody听($300)
The Technology: Instead of independent sheets of insulation like the other jackets on this list, CoreLoft Continuous (which is exclusive to Arc'teryx)听is a series of long听hydrophobic synthetic fibers that are strung between spaced out seams (picture the way strings in a听tennis racket are held in place).听听
The Results: The outer fabric on the was more wind resistant than many of the other jackets, so it was great for high-alpine ridges or cold, blustery parking lots. It breathed well when temperatures were in the 20s, but it was too warm once things climbed above freezing. 听
Best For: This is the midlayer you want on really cold, high-alpine backcountry days, or under a shell for riding the lift.
Black Diamond Deployment Hybrid Hoodie ($160)
The Technology: The uses PrimaLoft Silver Hiloft, a synthetic insulation that stays together on its own, and is sandwiched between a mesh lining and a breathable Schoeller softshell fabric on the outside.
The Results: Like the OR Deviator, this jacket mixes two different kinds of fabric. The PrimaLoft sits on the chest and top of the arms, and a stretchy merino is used on the back, around the waist, and under the arms. It was my favorite jacket for variable conditions because it kept me warm and protected around听my core,听but breathed better than the Acr鈥檛eryx Proton LT or the Rab Alpha Direct thanks to the merino fabric.
Best For: If you like all-day backcountry ski tours, where you鈥檙e starting out cold but warming up as the day goes on, this is your jacket. 听