Balancing the right technical features of a shell for fast-paced mountain pursuits must be difficult. You need something which can withstand the harsh conditions that mountain environments throw at you, yet still feel comfy and breathable. It should be light and compact enough not to weigh you down or take up excess space in a sack, and the necessary features should be as functional as possible, without having too much of an impact on weight and breathability. As Patagonia's lightest technical shell, the Ascensionist Jacket aims to strike this balance for high aerobic mountain days. I've put it to the test in a variety of conditions across autumn and the early winter season in Scotland, both walking and climbing.

Fabric

Patagonia have used Gore-Tex Active, a 3-layer laminate which Gore say is the lightest and most breathable of their 3-layer collection. The 30 denier nylon face fabric feels suitably thin for a shell this lightweight (363g in my size Medium), which has been welcomed when weight and space are a focus in a full winter sack. When I have been building up a sweat on the uphill, the Gore-Tex Active has been great for allowing this to permeate out, and it feels more breathable than a similar lightweight shell I used previously, which I would often end up having to take off. The dry feeling inside the Ascensionist also seems to be helped by the 'C-Knit Backer' inner face of the fabric, which is soft and comfortable and keeps the fabric off the skin well, even when only wearing a base layer beneath.

Add a DWR finish, and unsurprisingly, the Ascensionist feels easily waterproof enough for use in prolonged rain - and I've used it in a Scottish autumn and winter, which has to be one of the tougher testing grounds for a shell.

I would say the fabric lends itself to more alpine-like days where moving fast is key, and it's light enough to carry just in case even if adverse weather isn't expected. Because it's so light I would be cautious of taking this jacket on repeated technical mixed climbs, or even on multi-day excursions with a heavy pack. It isn't designed to be a heavy bombproof shell. For all-round hillwalking, though, it's ideal. And in terms of Scottish winter climbing, I look forward to big spring-like days later in the winter season, which I can see the Ascensionist will be well suited to.

As this is Patagonia, it should be no surprise that the Ascensionist has been designed to minimise its impact both on the environment, and on the people involved in its manufacture. The fabric is 100% recycled nylon and Fair Trade Certified™ sewn. The certified Bluesign™ approval provides the highest level of consumer safety to certify that the methods and materials used in manufacturing minimise impacts on people and the environment - something which has made the Ascensionist feel that bit more comfortable when wearing.

Fit

Available in five sizes (XS-XL), and in both men's and women's models, most people should be catered for. I opted for a men's medium. I do normally prefer a slim-cut jacket, given my light build, especially when wearing little underneath the shell. The straight cut feels a little boxy on me, with a slightly baggy waist. In that sense it's quite typical of North American clothing! However, with a few layers on at a belay and my gloves stuffed into the interior stretch pockets this extra room is welcome.

The articulated arms work well for my arm length and build, with the sleeves not pulling tight at maximum reach, or resulting in any significant hem lift or bunching of the jacket over my harness. Gloves can easily be placed underneath the cuffs and a standard hook and loop closure secures these nicely to avoid any wind, rain or snow getting in.

The drop hem at the waist sits over my bum and prevents the risk of any exposed region between the jacket and trousers even when stretching or climbing. This also incorporates a small skirted region which I really like when drawn in, as it channels the rain directly off of you instead of just letting it run down onto your legs.

The neck is a good fit, covers my chin when fully zipped and hugs my neck nicely. When the hood is up this area feels like an independent unit to the rest of the jacket when rotating my head, which I like. The hood is helmet compatible, with an easy to use drawcord at the back when using it without a helmet. In cold windy conditions I've appreciated the two easy-to-adjust side drawcords with the visor combo to keep the wind from penetrating.

Features

As the Ascensionist Jacket is designed for high aerobic activity it is no surprise to see two-way pit zips - these have been been great for venting when working hard and are an appropriate length to stop any rain getting in. These watertight zips are easy to quickly yank down with one hand whilst on the move.

There are two large interior stretchy mesh catch all pockets at the belly which, as I mentioned earlier, are great for gloves and could also fit a set of skins if you're out ski touring. If not using these then they provide no noticeable bulk. An exterior welted chest pocket is large enough to fit a snack, headtorch and phone which I generally want on hand and easy to access.

The two handwarmer pockets are large and high enough to still allow access with a harness or pack waistbelt on. Inside each of these are the draw cords for the hem, which I am still undecided about. I was really pleased to see these concealed, as I have had draw cord loops on many other jackets get accidentally clipped through a piece of gear on my gear loops - an infuriating situation on the lead. However, the actual draw function of these is a bit less 'intuitive' than Patagonia state. The cord itself requires you to draw it quite far out of the pocket and the desired tightness is often a bit looser than you necessarily want, as there is a slight difference at where it's 'set' when this 'bites' the elastic. The locking button 'Cohaesive' system for these is however something which I really like as they are easy to use and find around the waist. I didn't think I'd ever have so much to say about a draw cord.

Finally, a concealed Recco® reflector at the back of the neck is something which many skiers and alpine climbers will like but hopefully never have need for. In the event of an avalanche this makes you searchable to a rescuer (via a Recco detector) which will bounce a signal back to the rescuer. This signal becomes stronger the closer the detector gets, allowing them to pinpoint your location. These require no power or activation to function, should last a lifetime, and do not age or wear out (if undamaged). Thankfully I have not needed to test this.

Summary

Since it's not built for the abuse of mixed climbing I wouldn't recommend it as your main Scottish winter climbing shell, but for fast-paced mountain activities in less than full-on foul winter conditions, the Ascensionist Jacket is a big hit. Its highly breathable fabric is comfortable on the move, and boasts ethical credentials. The fit allows for technical climbing, it's compatible with a harness and helmet, and although boxy on me, it should suit most others. Features are there where needed, with an appropriate number of pockets and venting for high intensity days; but you don't get anything unnecessary. With their lightest technical shell, Patagonia seem to have a sweet spot that should equally appeal to Alpine climbers, ski tourers and hillwalkers. It's just a shame that this lightweight shell costs as much as many heavyweights!