Thoughts on the Synthetic Mid-Layer

I've been rocking an Arc'teryx Atom Lt that my mom picked up from Costco( yeah that's right) when I was 14, for the past 12 years.

I've managed to extend it's practical lifetime by practically replacing all of the face fabric on the sleeves with nylon gear tape, but at this point the insulation is so packed out that the jacket is basically just a "thermal placebo" that keeps me "warm".

I'm starting to reconsider what I believe to be the point of an active mid layer, and have had good success wearing an R1 fleece, coupled with an ultralight wind jacket (sierra designs Houdini knock-off). This systems does great at regulating temperature on very fast uphill movement, and for general endurance training, and as it is a two layer system is more versatile than the Atom LT which combine elements of both to provide a reasonable compromise between insulation, breathability, and wind resistance.

I'm starting to think that maybe if I am to replace my Atom LT with another jacket, that maybe I should look for features that accommodate this new system. The ideal jacket would be lightweight, packable, and capable of trapping heat between periods of movement. Ideally it would also serve to provide latent insulation when standing around for more technical missions where belaying becomes part of the routine.

The Nuclei FL, seems to fit the bill, along with the RAB Proton, but they are very distant cousins to my beloved, but dying Atom Lt. In an ideal world where I had the money and means, I would have a quiver of jackets for every style of outdoor activity, but currently I am stuck having to decide on just one jacket for everything.

So Mountain Project, what jacket would you choose in this category if you had to pick only one? Something that would last a decade, look good enough to take on a date, and provide versatile utility in the mountains?

R1 + wind jacket is hard to beat. Do you want more insulation from the new jacket?

Wictor Dahlström wrote:

R1 + wind jacket is hard to beat. Do you want more insulation from the new jacket?

I think that's what I'm struggling to decide. The Atom provides a decent amount of insulation, but if it's going to be replaced with something that's not a "stand alone" piece then maybe I could benefit from not having the underarm fleece and the side stretch panels. 

Puffy active midlayers have really limited utility IME— outside of extreme cold conditions (high altitude/winter mountaineering), fleece + wind layer (including fancy fleece like polartec alpha) is warm enough for active use, breathes better, dries faster, and offers better mobility.

For 3 season stop/camp/belay use on a budget the decathlon Forclaz trek 100 is a pretty fantastic deal— $80, ~10.5 oz, 3.3oz of 800fp down (as warm and lighter weight than jackets twice the price)

Dirt King wrote:

I think that's what I'm struggling to decide. The Atom provides a decent amount of insulation, but if it's going to be replaced with something that's not a "stand alone" piece then maybe I could benefit from not having the underarm fleece and the side stretch panels. 

tech fleece under a houdini type of thing is a winning combo as a baseline, but if it's not enough insulation or rain barrier you're looking at a 4th layer which can be tough to manage if the pace is changing a lot throughout the day. i think that's where the good standalone jackets shine is they are able to cover a wider range of conditions without stripping down or adding layers. it just depends on the conditions obviously one jacket can't do it all

fwiw i rock a wool shirt, tech fleece, houdini as my go to. sometimes trade the fleece for light puffy if it's colder, sometimes trade the houdini for a rain layer if it's wetter. i also live in southern california so who cares what i think about layering really

I intressed in the topic, but I have used baselayer + R1 + wind jacket ice climbing in -20 C/-4 F. They I use a belay jacket when not moving. I have looked at things like the Patagonia Nano Air and similar, but that would mainly be to replace the R1 and win jacket in extreme cold.

The Atom LT is’t really optimized for use as an active mid layer or a passive outer layer.   I view it more as something that is designed to be used for moderate intensity (like walking on flat ground).  

An R1 works better as an active mid layer, because it is more breathable.  A Nuclei FL works much better as a passive outer layer, because it has a wind shell that doesn’t allow trapped warm air to escape.  

If it is cold enough, I generally carry two separate insulating layers, one relatively breathable active insulation layer (such as a R1) and another non-breathable passive insulation layer (such as a Nuclei FL).

Karl Henize wrote:

The Atom LT is’t really optimized for use as an active mid layer or a passive outer layer.   I view it more as something that is designed to be used for moderate intensity (like walking on flat ground).  

An R1 works much better as an active mid layer, because it is much more breathable.  A Nuclei FL works much better as a passive outer layer, because it has a integrated wind shell that doesn’t allow trapped warm air to escape.  

If it is cold enough, I generally carry two separate insulating layers, one relatively breathable active insulation layer (such as a R1) and another non-breathable passive insulation layer (such as a Nuclei FL).

This is kind of what I'm leaning towards, I just wish they made the Nuclei in black so I could wear it to dinner (very petty complaint), but that might be the route I take. Do you have any experience with the RAB Proton?

Dirt King wrote:

This is kind of what I'm leaning towards, I just wish they made the Nuclei in black so I could wear it to dinner (very petty complaint), but that might be the route I take. Do you have any experience with the RAB Proton?

No experience with the RAB proton.  

The Patagonia DAS Light is very similar to the Nuclei FL and it comes in black.  It also has roomier fit and a two way zip, which probably makes it a bit nicer as a belay parka.  

I prefer fleece, specifically Ortovox merino. 

I ditched the R1 type layers years ago: too hot for me and IMO obsolete now with the nano air style jackets available as a mid layer. I'll still use a light long sleeve base layer if the occasion calls for it (whether winter climbing or cooler weather rock climbing, plus a wind/shell jacket). But for that next step up in insulation I skip the "fleece" as I find it bulkier, heavier, and less breathable. For alpine rock climbing I think the Atom SL is incredible: great mapping of insulation to keep your core warm and arms unencumbered; as a warmer step up for proper alpine missions the Proton FL is pretty killer. If it gets quite windy or precipitation starts to fall, just throw a wind jacket or light shell on top. *I know it sounds weird to say an R1 is less "breathable" than these jackets, but I find the looser fit and insulation of them moves air around and keeps me dry feeling, whereas the snug fleece layers keep me clammy while I'm working up a sweat. Fleece also snags more vs the nylon face fabrics.

I've also tested the Rab Xenair Alpine Light and wrote a glowing review for Climbing, not sure if it got published. Basically its a bit more midnight but has a nice burly face fabric that has held up super well across disciplines (Yosemite, red rocks, ice climbing, & skiing) and seems to insulate and breathe as well as the aforementioned Dead Bird options.

EDIT TO ADD: The Rab Xenair review is in Climbing Print Issue 381, apparently

A few years back, Patagonia made a lighter version of their Nano-Air hoodie, called (appropriately enough) the Nano Air Light Hoodie.  

This is my favorite piece for winter when it's cold.  The Nano-Air Light breathes well and is not too hot for active use in cold temps, and it provides enough warmth for short stops when you're not active.  (For longer stops, I layer a puffy jacket over everything, then shed the puffy when I'm ready to move again.)    It's my go-to ice climbing piece for cold temps.  

Sadly, Patagonia seems to have discontinued this piece of kit. 

For three season use, I find just about any insulated clothing too hot when I am moving.  I generally just wear a light weight (often long sleeve) base layer, and throw on a Houdini-like windshell or lightweight softshell over that base layer to fend off high wind or light precip.   When I stop moving for longer periods of time, I put on an insulated puffy appropriate to the prevailing temps.  

Bottom line is that for me, most every synthetic mid layer is too hot for active use in anything except the coldest temps.  

MauryB wrote:

I ditched the R1 type layers years ago: too hot for me and IMO obsolete now with the nano air style jackets available as a mid layer. I'll still use a light long sleeve base layer if the occasion calls for it (whether winter climbing or cooler weather rock climbing, plus a wind/shell jacket). But for that next step up in insulation I skip the "fleece" as I find it bulkier, heavier, and less breathable. For alpine rock climbing I think the Atom SL is incredible: great mapping of insulation to keep your core warm and arms unencumbered; as a warmer step up for proper alpine missions the Proton FL is pretty killer. If it gets quite windy or precipitation starts to fall, just throw a wind jacket or light shell on top. *I know it sounds weird to say an R1 is less "breathable" than these jackets, but I find the looser fit and insulation of them moves air around and keeps me dry feeling, whereas the snug fleece layers keep me clammy while I'm working up a sweat. Fleece also snags more vs the nylon face fabrics.

I've also tested the Rab Xenair Alpine Light and wrote a glowing review for Climbing, not sure if it got published. Basically its a bit more midnight but has a nice burly face fabric that has held up super well across disciplines (Yosemite, red rocks, ice climbing, & skiing) and seems to insulate and breathe as well as the aforementioned Dead Bird options.

Hi Maury--I'm intrigued by the Rab Xenair Alpine light.  Sizing question: how roomy is the fit compared to the Arcteryx Proton FL? Could you wear both inn the same size? Also, the hood says helmet compatibile, but is it a tight fit over a helmet, or comfortable?

I would actually be using this as a lightweight belay jacket, so a roomy fit and a nice over-helmet hood would be important.  I've tried on the Patagoinia DA light, and, much to my annoyance, it seems as if they have sized it to be more of a mid layer and less of an outer layer, so if the Rab was a little bigger, that would be great. 

Other thoughts for lightweight, roomy, synthetic belay jackets?  

Bruno Schull wrote:

Hi Maury--I'm intrigued by the Rab Xenair Alpine light.  Sizing question: how roomy is the fit compared to the Arcteryx Proton FL? Could you wear both inn the same size? Also, the hood says helmet compatibile, but is it a tight fit over a helmet, or comfortable?

I would actually be using this as a lightweight belay jacket, so a roomy fit and a nice over-helmet hood would be important.  I've tried on the Patagoinia DA light, and, much to my annoyance, it seems as if they have sized it to be more of a mid layer and less of an outer layer, so if the Rab was a little bigger, that would be great. 

Other thoughts for lightweight, roomy, synthetic belay jackets?  

The Rab piece is definitely a slim, active fit - much like ether Proton FL. Sizing is about the same (I'm a nearly universal medium). The helmet compatibility was my one ding: it will NOT fit over a helmet, its snug even just pulling over your head. But it fits UNDER a helmet nicely. (I have a small/medium head)

If you want a lightweight, roomy, synthetic belay jacket its not your piece - I'd go with the DAS Light, which is also trim enough to climb in. But if you want a proper shoulder season, active midweight piece the Xenair Alpine Light is a great option.

@ Maury--thanks, just the info I was looking for.  Sometimes the internet works!

The ultimate comfort solution is any sort of breathable fleece (i use the mountain hardwear airmesh) with a wind jacket (bd alpine start) when I'm moving and zip/unzip to regulate. All pretty typical so far but at belays I pull out my secret weapon which is a down vest I got from aliexpress (naturhike 1000fp down vest) which compresses down to a literal orange that I have in a stuffsack hanging from my harness. Stuff a sandwitch in one shoe and a collapsible water bottle in the other and you are set to be happy and full all day :) 

Thanks all! Lots of great suggestions, I'll take a look around and see what I can get a deal on, shame that Costco doesn't carry dead-bird anymore!