All the major outdoor brands have at least one insulated midlayer/shell in their range. There are plenty of advantages to this style of jacket for climbers: warmer than a soft shell, more windproof than a classic fleece, light as a feather and much more compressible than either a fleece or soft shell for squeezing in your pack. They even offer some water repellency. I have actually been using a synthetic fill vest as an additional layer between my fleece and hard shell for several years now, and find it excellent for climbing in - the lightweight layer is unobtrusive and warm.
So I decided to get myself the Armani version of the jacket style - the Arc'teryx Atom LT. Arc'teryx needs no introduction to climbers. The brand is famous worldwide for their relentless obsession to quality and innovation. They lead and others follow, they bring out the clothing and we drool, slobber and max out the credit card.
The Atom LT is the lightest in the range of three Atom Arc'teryx jackets. Its stated weight is 326g and on my kitchen scales it weighed in at 324g. It feels absolutely featherweight, and is in fact, 129g lighter than my usual fleece/windproof combo and 114g lighter than a shelled microfleece from a reputable manufacturer. So I'm saving a lot of weight for no loss of warmth. The jacket felt warm in all the conditions I wore it in, from belaying on cold autumn days, to standing around bouldering on windy autumn days to hill-walking on damp autumn days.
The attention to detail is as impressive as you would expect from Arc'teryx. The Luminaria shell material is very light yet feels tough. It sheds light showers with ease, and still feels warm, even when damp. Insulation is provided by 60g of Corelight synthetic fill, and this felt sufficient on all but the coldest of days. The breathability is excellent, even when hill-walking; in fact for hill-walking / mountaineering the top was totally brilliant. Usually, when walking, I wore just a t-shirt on underneath or a light merino wool layer. With a Paclite jacket in my pack in case it rained, that was it, I needed nothing else.
The pockets are fleece-lined so my hands kept toasty and the fleecey collar also felt snug and warm. The cuffs are fitted around the wrist to keep the wind out. Gloves fit easily over these cuffs, and they also work with under-the-cuff style gloves; creating a nice tight seal and keeping the warmth in. In fact, on a recent ice climbing trip to Cogne I wore the Atom under a soft shell and felt plenty warm in temperatures down to -8 degrees all day. It worked brilliantly under a soft shell, with the material sliding under the shell to give a great climbing movement - much better than a 100 weight classic fleece.
The Atom was extremely packable, I easily fitted it into its internal pocket and I even got it into an Exped XXS sized bag! Here it is packed into its pocket.
Ed's note: while the Atom does fit into its internal pocket, its not designed to be packed this way, so you can't send your jacket back to Arc'teryx if you break the pocket zip! The UK's Arc'teryx technical expert, Mark, suggests you pack the Atom into its sleeve; this has the added benefit that you can kind of ping it back out.
The jacket was excellent for climbing in. The cut is very athletic and body hugging, while the Powerstretch panels have Hardface technology, which further enhances the already excellent Powerstretch material to make it tougher, even more breathable and gives it a soft shell like water repellancy. These panels are stiffened at the bottom using a laser cut and laminated insert that keeps the jacket tight around the waist area, so no need for a hem cinch. The Atom has minimal rise, even with my arms fully extended it provides an excellent fit, especially with a harness on, when there is little rise or ballooning at the chest.
The zip has worked under all conditions so far, although the insulated windflap does catch occasionally. It's a YKK Watertight Vislon zip and has a very smooth operation - even one handed with gloves on. There has, apparently been issues with the zip, I've had none at all, it's worked well every time.
Carl Moriarty, the designer, responds to Dave Sarkar's comments about the zip:
"The number 3 Vislon zipper on the Atom line does not have a locking slider. We had concerns about the long term durability of the zipper teeth when subjected to the forces of the locking slider. The 3 Vislon as it is in the Atom has proven to be significantly more reliable and durable than the 4.5 coil alternative.
We have had many of these jackets out in the field over the past 2 years and while several people questioned this zipper early on, no one reported it to be a problem after use. The more we speak with those who've been using the current zipper the more we like it! For the garment's intended use in layering it has some advantages. It's very easy to open the garment one handed, which is great when you have it under a shell or locked in under shoulder straps. This makes it easy to vent and very easy to retrieve items from internal pockets. It's smooth and incredibly reliable for its weight and suppleness."
That's it! I've thrown out all the fleeces as I don't need them any more. This jacket does everything. It keeps me warm even when I'm damp. Packs down to nothing and weighs so little I feel I have to anchor it down. It's beautiful to climb in, is unsurpassed in mountaineering and hill-walking situations and I cut a dashing figure down the pub in it. The only thing better in my opinion would be the Atom LT Hoody! It's all you would expect from Arc'teryx, a cleverly designed jacket with all the features a climber and mountaineer would need. But be warned, it is not a UK winter/ice climbing belay jacket.
See this product at the Joe Brown - Snowdonia shop