Saturday, 30 June 2012

Arc'teryx Atom LT Hoody Initial Analysis

There is no doubt that down has the optimum warmth to weight ratio. When properly lofted, a down jacket or sleeping bag will be warmer per gram than any synthetic warmth provider whether that be Primaloft, Coreloft or a fleece derivative. Yet down has that one near fatal flaw which means it requires sensitive handling and protection - it is utterly useless when wet. It can also degrade each and every time it is wet and then subsequently dries. Therefore, it has always been my practice, for an active insulation layer which I can throw on and not worry about, to choose synthetic fill insulation. I reserve down for wild camping in winter when my base and mid-layers are generally warm enough on the hill when moving but which I remove when in camp. For that role, my PHD Yukon has proved almost infallible.

So when Arc'teryx sent me an Atom LT Hoody, I was keen to see how it stacked up against the Patagonia Nano Puff and the Montane Prism 2.0 I had previously been using. I took it to Jotunheimen in Norway as my sole insulation against the harsh Norwegian weather.

I have a Rab Generator gilet for scrambling and climbing which is a size larger than I need normally as it goes over the top of everything - it is a summit and belay piece so unfair to compare it to the Atom which fulfils an entirely different role.

The Perfect Insulation Layer
What am I looking for from an insulation layer? For a 3-season 'summer' layer, that is to say everything outside of winter, I have several quite simple criteria. Firstly, apart from keeping out the wind and keeping me warm (its core mission), it should be lightweight but reasonably hardwearing. It is likely that, on shorter trips as well as long treks, it will be an active warm layer as well as a camp layer, so my rucksack will be on it and I'll be moving in it. For a hooded insulation layer, with 60g weight insulation, I think that 400g is the maximum weight a garment should be. It should pack down into a relatively small bundle easily and, equally easily (and swiftly), be available for use again. The arms should be articulated to allow full range of movement as I might be climbing or scrambling in my insulation layer. The back and waistline in general should not ride up and the hood should be simple, easy to deploy and manage and not have oodles of ridiculous and cumbersome toggles to adjust it. hand pockets are a good thing as I don't always want to get gloves out for only a short period. Cuffs should shut out the wind and be comfortable without restricting movement. The neckline should be sufficient to protect my neck from the wind but not annoy me whilst moving. I don't need interior pockets - I never use them nor do I need the ubiquitous Napoleon pocket seemingly attached to every garment ever made by an outdoor manufacturer.

So, onto the Atom LT Hoody. At 368g for a size large (my weighing), it packs down into its own sleeve. See the video here for how to pack it down but let's be real about this - this is not a design feature, it's something (I suspect) developed by a rather clever Arc'teryx sponsored athlete and adopted by Arc'teryx rather than the Prism and Nano-Puff which are designed to pack into their own pockets. Still, it works well enough and it's one less feature to worry about. Also, it does indeed deploy simply by shaking the sleeve. I rather like that. I am a 39-40" chest, 34" waist and my torso is 21". A large is the perfect fit for me.

The Atom LT Hoody has the following features:

  • A lightweight, breathable, wind-resistant, moisture resistant (DWR-treated) outer fabric (Polartec Powerstretch Hardface);
  • Stretch side panels (under the armpits and down to the hem) which allow articulated movement but keep the garment reasonably figure-hugging;
  • Insulation which has good warmth for 3-season use and which behoves a packable, compressible garment;
  • An insulated, sculpted, scuba hood which will fit under a helmet;
  • A full front zip with a wind flap;
  • Stretch knit cuffs;
  • Embroidered 'Arc'teryx' hangloop;
  • Dropback, laminated drawcord-adjusted hem; and
  • Two hand pockets with an internal chest pocket.

Fabric Magic
The Atom LT series is made from Polartec Powerstretch fibres with Hardface Technology. Hardface was developed by Polartec for its own fabrics and it is designed to enhance the DWR coating of their fabrics, increase their durability particularly when it comes to snag/abrasion resistance and create a smooth surface to make layering easier. This is innovative and targeted thinking from Polartec and the evidence in the form of the Atom LT series is cogent. The surfaces of the Atom are smooth enough that it's easy to get on and off as well as put other layers on top of it. This is crucial as cold fingers make hard work of shrugging on an insulation layer which may need to be done with some alacrity. I have yet to snag the Atom despite some rough treatment and the fabric shuts out wind well and breathes sufficiently too, probably assisted by the fleecy, stretch side panels. Water beads off it well enough but this is a new top, with a good, new DWR - I would expect water from a frisky shower to bead off it at this point. How it performs after months of use is another thing but frankly, no fabric on a lightweight insulation layer is designed to keep out anything more than a quick shower and certainly not after months of use - no DWR "water resistant" coating is that good. This is not a waterproof shell layer - let's be realistic about what fabrics can achieve.

Rather than using Primaloft, the most well known insulation filling around, Arc'teryx use Coreloft. As to why, they say this:  "Coreloft is a fabric that we have made for us. It's similar to Primaloft, but we have tweaked a few things to try to get better performance. Core Loft is constructed of a double strand of continuous polyester filaments. The finer yarns (1 denier) are "crimped" to help trap air molecules which in turn help trap body heat while the larger yarns (3.5 Denier) provide loft and resilience from compression. The fibers are siliconized to help add resistance to moisture and decrease drying time." I've read several reviews suggesting Coreloft breathes better than Primaloft but, really, I can't say either way. I haven't used the Atom long enough to say, and it is so utterly subjective and incapable of controlled analysis that I doubt the difference is significant. There is a typically detailed discussion on BPL here which delves into that US-style minutiae which has become so popular. What I can say is that the Atom breathes perfectly well and kept me every bit as warm as the Prism 2.0. The insulation itself also spreads to the front of the hand packets meaning that there are two layers of insulation for cold hands. This, to me, is essential thinking. It also spreads to the hood - again, essential thinking.

Other Features
The Atom LT Hoody has a number of useful features outlined above so let's have a closer look at them. The armpit/side stretch panel material (shown in the photo above, next to the hand pockets) keeps the shape of the Atom consistent and athletic. The hand pockets have wind-break zips and a fleecy lining. The simple hood has an elasticated rim which sits comfortably around the face without protruding into the eyeline. There are no adjustments to it which, on a lightweight insulation layer like this, is a good thing. The stretch cuffs are neat - no adjustment potential, just a comfortable, smooth fabric which sits snugly hugging the wrist without being uncomfortable. I'd be concerned about durability of the stretch over time, but we'll see. Weight saved through lack of adjustment tabs which is fine by me. I don't much like them anyway.

The zips all run smoothly and washing is easy. The interior lining of the stretch material under the arms is a thin fleece and the rest of the hoody's interior is ripstop without Hardface.

The dropback, adjustable hem is good and the drawcord is encased in protective ripstop nylon. Pull your arms upwards and the small of your back is not exposed. Simple and effective. Adjustment is relatively easy but of course, with gloved hands, the toggles are a little fiddly. Zip pulls are not, however, with good sized tabs on a decent length cord. I cannot see the point in the internal chest pocket but some people may find it useful. It's big enough for a snickers or a compass, if you like that sort of thing. Also, in the photograph below you can see the ripstop inner lining to the Atom.

I found the Atom LT Hoody to be an effective insulation layer. It kept out the wind, kept me warm even in pretty chilly weather and even kept out a short shower. It packs down around the same size as the Prism although into a sausage rather than a neat package. I can live with that and I like the sleeve-shake deployment. I cannot speak as to durability of the fabric yet - I'll do that when I update this IA with a Review after a few months of solid use. The attraction is the weight - for a good face fabric, 368g is a good weight for a 60g/m2 insulated hoody. There's nothing to complain about so far as the Atom LT Hoody is concerned and when you compare weight to functionality, it's better than the Prism 2.0 and the latter uses 40g/m2 Primaloft ECO but still weighs in at 418g for a size large. The Nano-Puff may be lighter but it does not have a hood and its certainly not as warm in my experience. The Atom will be in my pack for a long time to come.


  1. The perfect summer insulation piece? I looked at the Prism too but it seemed a bit overweight for it's insulation and I seriously considered the Atom which looked very well made, but in the end I went for the lighter, simpler Rab Xenon. 60g Primaloft, great hood, perfect cut and packs to nothing. Plus it's available in such pretty, pretty colours...

  2. The Xenon is superb and Lord knows I love Rab, but on this occasion I prefer the Atom for several reasons - firstly Pertex Quantum is very lightweight but I always concerns about durability (I have two Infinity products). The Atom simply feels more durable and the Hardface fabric feels like it will deal with rougher use like the abrasion from a rucksack, for example. I also wonder if Polartec Hardface will be more water resistant in the long run. Secondly, I prefer the cuffs on the Atom - more comfortable and they shut out wind better. Not sure I am worried about the difference in weight of 20-30g. I can't argue with the colour point - Xenon wins there... Let's meet in Norway next summer and we'll compare.

  3. What Rab should do next is offer an Endurance skinned version of the Xenon (Lord knows I've asked them enough times) like they did with the Alpine Generator. I hear what you're saying about the Quantum but I've found it durable enough in 'summer', so far... I know you like scrambling around on rock so maybe your criteria is different to mine. I would almost never hike in the Xenon under pack straps so it really is just a warm layer in camp for me. If I need some 'active' insulation then a very simple fleece vest is my choice (the only time I go against my 'one way layering' principle). 

    Yeah, next year will be nice in Norway, I promise. This year summer and winter haven't agreed the terms on their handover of the Hardangervidda yet...

  4. Horses for courses, I agree. I have work to do in
    Norway next year so I need some great weather and the likes of Gauperaa, Fisher and yourself (as well as Morkel if he can drag himself over) for company.

  5. Wow, that's a great (and thorough) post, thanks so much! Love the photography, too.

  6. I have to admit that I have been lusting after one of these jackets for a while now.  You have not helped matters!  Its just a shame that Arc'teryx is so damn expensive.

  7. It's a great all round insulating layer - reasonably good face fabric, good insulation, not overburdened with silly features and a good fit. I suspect, James, you'd be the same size as me. True enough that Arc'teryx is expensive - perhaps the only flaw, but they say you're paying for innovation and quality. I'd agree with the essence of that certainly.

  8. What color is this?  Tungsten?  It looks almost blue.  And is this one of the new colors, or an older model?

  9.  So, does it look blue because the photo is saturated or is it actually a bluish color?  I am looking for very drab/subdued colors for fly-fishing and the last round of Atom LTs were very loud and obnoxious...  Would you recommend this as a dull color?

  10. The colour is very much grey with a hint of blue. It's a dull colour but I don't see it as an option on the Arc'teryx website. I would email them and ask but the colour in the images on this post are accurate.

  11. i just bought 3 atom pullover bloody nice best mid layers 


  12. I found your blog
    on Bing , this is a nice blog , i will come back.

  13. A very thorough review. Many thanks.

  14. Hi,
    could you tell me please how do you wash it?
    Do you use and product?