Marmot Isotherm Jacket with Polartec Alpha Insulation

Polartec’s Alpha technology is one of the new stories for this year. The basics are that it’s a lightweight low volume synthetic fill that’s designed to work across a wide range of temperatures and conditions.
I got a Marmot Isoterm Jacket in to test last winter as an example of the technology and as it’s a medium it’s been working as a slim fit on me and a relaxed fit on Joycee. It’s been around and lived a full life, poor thing. What’s the results then?

The Isotherm is a regular jacket design, no hood (a hoody is available) and low-set hand warmer pockets. I don’t really mind low set pockets, and here the tops of the pockets are set high enough to slip my hands into when I’m wearing a rucksack. The pocket entries are set well back towards the side seams as well as having deep pocket bags, so these are big badass pockets to take all your niknaks and more.
There’s a chest pocket which is external and stretchy, not too big but plenty useful. The same stretch fabric is used elsewhere as zipper garages on the pocket zips, a nice wee touch, and also on the shoulders, where it’s doing something, not sure what. The arm articulation is pretty good so I’m not sure overarm stretch is needed so I’m going for durability, the rest of the shell is Pertex Quantum and the stretch panels will take all the pack shoulder strap abuse.

The Pertex is as you’d expect, light, silky, packable with decent water resistance. It’s stronger that you’d think as well, I’ve torn Quantum on barbed wire, where it did indeed tear along the ripstop lines making for an easy repair, but in general use it last well against regular abrasion.
The collar is medium height, the main zip has a stiffened baffle and a chin guard. All the zip pulls have big pull tags on there and there’s a side-pull single hem adjuster which I’ve never used as the waist is exactly the same size as me. That’s “man sized” if you were wondering.

The outside is clean and slick but the inside is a patchwork of fabrics, all there to help the Alpha insulation do it’s thing. In amongst more lovely orange Pertex the mesh is DriClime, a long standing Marmot fabric. Who can forget the DriClime Windshirt with the horizontal chest pocket that only fell runners can understand.
The mesh is sensibly placed to try and keep you dry when you start pumping sweat out, almost all of the back has it and the upper chest at the front.

Then there’s the Alpha in the middle which Polartec say is based on “Polartec® Thermal Pro® High Loft technology platform”. I say that when you hold it up to the light it looks like a string vest made of tiny fleecy strands. So I’m going with that, techno string vest.
But, that’s not a bad idea. In winter I like wearing a base, a microfleece and a windshirt or light shell. Alpha is kinda giving you that all in one, because although Alpha is billed as insulation, it’s really on-the-move warmth or good weather insulation, it’s just not that warm as a camp jacket. Again, not a bad idea. Throw the Isotherm on at the start of the day from now until spring and until it really pisses down with rain the only clothing changes you might make are to pull on a warm jacket at lunch or camp.
I know there’s plenty of all-in-one systems like this around, Pertex and Pile, Paramo and more, but it’s the lack of warmth that I like here with the Alpha. I’m getting the comfort levels I’m used to but I’m getting it with less kit and less weight. A good thing yes/no?

322g for a medium, compare well to a microfleece and windshirt combo and it compresses down well for packing. How it will age I’m not sure, there’s no loft to monitor, so I suppose I’ll just watching for the internal string vest to come apart and fall down to the hem in the future.
The sandwich construction does make drying times longer than they might be, a windshirt and microfleece dry quicker when separated. The Isotherm layers very well, great over a baselayer and under a shell or heavier insulation.
It all works perfectly well, the fabrics used and the Alpha insulation are a perfect match, the detail and quality in the Marmot design and construction is excellent. But, I kept on looking for pitzips to cool down and the lycra bound cuff don’t quite pull up to my elbows. For me one-pieces still aren’t adaptable enough for the range of temperatures my motor runs at.
But if you like your lightly insulated Pertex, you might well love this.


17 thoughts on “Marmot Isotherm Jacket with Polartec Alpha Insulation”

  1. Ha, snap again..
    I got the isotherm hoody to test, waiting waiting waiting for cold weather down under…. never got cold enough to keep it on long enough for a decent test. took it up to 3000m, 10 degrees on a sunny breezy day, still to warm.. now i have to hand it back….

  2. winter was largely a non event down under, blink and you’d miss the cold weather…. i only had it on loan for a short time… only had one trip to a cold region during the time. weather didnt play ball… at 3000m it was so hot i went through 3 litres of water….

  3. I’m amazed they still want to send you any at all!
    Aye, it’s gamble given my recent review speed :o)

    That just isn’t a winter at all. We’ve been lucky the past few years, great winters one after the other. Hoping for more in a few weeks too.

  4. Haven’t found any of this Alpha stuff that I really like yet. I tried on a hoody version of the Isotherm and found it to be ludicrously short in the arm, finishing 4” short of my wrists with my arms at my side! This was in the otherwise Ok- fitting Small size, the Medium barely any better but far too baggy to be of any use, oh well…
    No-one seems to have grasped Alpha’s main advantages – it’s breathability and stretchiness. Why hamstring these properties by covering it with rigid, totally wind-proof fabrics? This makes these jackets feel like just another warm but clammy insulated jacket.

  5. I’m still on the fence in some ways, it’s good but is it really any better than what we’ve got?
    I’d like to have a set of gloves or mitts with it, nice low profile but warm with it.
    We’ll see where they end up with it I suppose.

  6. The only item I’ve seen which actually seems to be using the Alpha properly is the First Ascent Propellant Jacket by Eddie Bauer. Simple design and a stretchy outer face, looks good in the only available colour scheme – grey with blue detailing. Not available in the UK though.
    I keep thinking to myself that I’m better sticking to my Smartwool PHD and Rab windshirt combo – more versatile and, since I’ve already bought it, not costing me anything!

  7. Aye, that’s a combo you can swear by. I couldn’t count the days I’ve spent just in a baselayer and windshirt. But they have to try and persuade us that the new thing is better than that of course :)

  8. True, so true. I’m keen on new technology and materials, comes of having an engineering background I suppose, but Alpha as so far utilised reminds me a bit too much of Paramo gear – nice idea but flawed in the actual execution of it, not so much ‘multi-functional’ as ‘eggs all in one basket’. When it stops working for you you’re stuck with it. If too hot you take it off to reveal nought but a base layer. I can’t believe it really works that well under a shell either.
    I don’t know if you’ve seen anything of the Patagonia Nano Air jacket, now that seems more like it if, like me, you run a bit warm and don’t want the windproof outer that’s been applied to all Alpha pieces so far. Seems promising and worth waiting until the autumn for, at least to check it out.

  9. I do tend to run a bit warm a lot of the time, either that or a I feel the cold so I do need flexibility. Old school layering’s got that just nice, the power to deal with me being at one extreme or the other!

  10. Hi Petesy, I finally succumbed to the ‘Alpha revolution’ for this winter and I have to say, after much faffing about trying to get it to work for me, that I think I wasted my money and my time!
    My first choice of an Alpha piece was the Rab Srata. I have found it OK if it’s at freezing or below but from say 5 *C or above it’s unbearably hot, even over just a thin base layer, no matter how windy it is. I think Alpha’s best use would be for true mid layer fleece-formatted items ( with 60 or even 40g Alpha ) to replace heavy, hard-faced garments with something as protective, but much lighter and easier to move in, rather than ‘upgrading’ belay jacket designs.
    With this idea in mind I was considering the new Strata Flex but the fit is awful, it has a cumbersome full zip and unnecessary pockets with exposed zip splitters ( on a mid layer that ‘s a recipe for shell jacket destruction! ).
    So, keeping an eye on new offerings but meanwhile it’s back to the fleece / wind-shirt combo for true versatility!

  11. You can’t argue with what works for you, doesn’t matter what the adverts say.

    Alpha is an odd one, I’ve found the newer jackets work better for me, but did we really need it in the first place?

    Currently testing another new (secret apparently) synthetic down fill for next year.
    I am unmoved by that as well!

  12. I think the designs and end uses for Alpha garments are all wrong, belay type knock-offs and ‘hybrids’ included. The insulation is one developed from ‘Thermal Pro’ – a textured fleece so surely more mid-layer fleece-type garments would suitable for Alpha. I find myself wondering why no-one has partnered it yet with Polartec’s Power Shield Stretch Woven variant which, with it’s stretchiness, would suit Alpha’s own properties well. Primaloft doesn’t work for me as a mid-layer and I don’t like trying to add on a ‘sticky’ fleece as an additional layer as it’s a struggle when it’s windy but something with a slinkier inner surface and a bit of extra weather protection from it’s outer surface as well as lighter weight/less bulk than ‘hard face’ fleeces …..winner! Shame no-one’s making anything like that!
    I presume the insulation you’re testing is another synthetic trying to pretend its down – as ‘blown in’ filling (yawn). I’m not sure any of these has a point beyond trying to sell more product which is otherwise indistinguishable from what’s already available.
    Interestingly, Patagonia went with Toray rather than Polartec with their ‘active’ insulation and Haglofs are apparently planning to do the same. I wonder if THEY will come up with anything useful!

  13. Ooh, ooh….. check out Henrik’s ‘Hiking in Finland’ blog. The latest trade fair report includes a snippet on Rab’s winter 15/16 stuff including something called the Paradox Pull-On. I checked this out via a search and well, THAT’s more like it! A piece that should work within a your system rather than trying to BE your system!
    Really, what’s been available so far is just belay style jackets warm enough to stop you freezing when stopped but too warm 90% of the time, i.e. when you’re moving. What’s needed is for everyone involved to get over that ‘put it on, keep it on’ nonsense and produce stuff that’s better than current designs in some way and doesn’t lock up your options in one non-adaptable piece.
    Now, if only Rab can get the fit right……

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