Mountain Equipment Aerotherm Jacket | Tested and reviewed

Designed for mountaineering, alpine climbing, hiking and even running, the Mountain Equipment Aerotherm is a highly-technical softshell jacket with a clever design reminiscent of the Rab Vapour-Rise Summit. It is billed as windproof and fast-drying, with a touch of added warmth, and high levels of versatility so “you can keep it on in fast-changing conditions”.

The outer is a super-light double weave softshell fabric, while the inner is a micro-grid of fleecy squares – an approach designed to give you the best of both worlds, warmth on the inside, weather protection on the outside. But the real USP of this jacket is its minimalist, ultralight construction. The men’s small weighs only 279g, which is incredibly light. For gram-saving hikers, it’s a revelation.

Fabrics & Stretch

This softshell is made from two main fabrics. The outer is an Exolite 45 stretch double weave softshell fabric (100% polyamide). Mountain Equipment says this fabric is “the lightest double weave fabric in the world”. The inner, meanwhile, is a micro-grid of fleecy squares (100% polyester). This wicking lining is designed to help regulate your body temperature and provide next-to-the-skin comfort.

Overall this dual approach is designed to give the best of both worlds - wind and rain protection on the outside, toasty warmth on the inside. There is no elastane in the fabric, so you don’t get anywhere near as much stretch or flex as you do with traditional-style softshell jackets. For some hillwalkers, the outer might feel worryingly thin and flimsy, but it appears to have decent toughness despite its low weight.

Wind-Resistance & Water-Resistance

This jacket does everything you’d expect from a softshell. It can cope with a light shower and offers a decent bit of water protection, but – as is the norm – should be paired with a hard shell waterproof jacket in heavier conditions. It protects you from the effects of gusting winds too, with Mountain Equipment stating “this versatile layer keeps out the wind whilst still offering a little warmth in exposed situations”.Breathability levels are very impressive too, with Mountain Equipment describing them as “exceptional”.

Fit, Comfort & Weight

This jacket is undoubtedly ultralight. It weighs only 279g in the men’s small, which is quite remarkable considering the levels of warmth and protection you get from the Aerotherm. Ultralight enthusiasts will love this gram-saving approach; others may feel the jacket lacks the robustness and heavy-duty protection they desire in a softshell.

As means of comparison, the Mountain Equipment Aerotherm is 44g lighter than its direct rival, the Rab Vapour-Rise Summit. But the weight savings are far higher when compared to traditional-style softshells. The Aerotherm is 256g lighter than the Alpkit Resolute, for example, and 248g lighter than the Keela Hydron.

In terms of comfort, the Mountain Equipment Aerotherm should be judged on two different criteria. If you want the interior of your softshell to feel plush, soft and cosy, the Aerotherm will probably disappoint you. It’s so minimalist and lightweight that the interior doesn’t give you those sensations. The gridded liner is comfy enough, but it’s definitely not as a soft or luxurious as the Rab Vapour-Rise Summit’s fleecy inner, for example. But in terms of all-day comfort, the Aerotherm hits the mark perfectly. It’s so light, airy and streamlined, you almost forget you’re wearing it – and that means it’s never bothering you, or causing little niggles, or getting in the way. It just does its job under the radar, and sometimes that’s all you need. Mountain Equipment describes it as “arguably our most comfortable softshell jacket”.

Due to its lightweight build, you probably get less of a warmth boost from the Aerotherm than most other heavier softshells. On cold days this may be a drawback, but in many scenarios it will help minimise the risk of over-heating.

The fit of the Aerotherm is described by Mountain Equipment as an “active fit with articulated and pre-shaped sleeves”. The cut is certainly snug and athletic, and – in truth – we found our normal size (men’s small) ever so slightly on the tight side, so perhaps in the future we would size up. But the small still worked pretty well for us.

Features: Pockets, Hood & Ventilation

Due to the ultralight build of the Mountain Equipment Aerotherm, you get some features but not everything you might expect. This is a clear trade-off – the ultralight weight is only possible by omitting a few standard features.

You do get two fleece-lined handwarmer pockets and one chest pocket, located on the left breast, for valuables. There are no internal pockets. The waist hem is adjustable via two drawcords, but the elasticated, stretchy wrist cuffs are non-adjustable. There is no Velcro at the wrists, but we didn’t really mind – the fit worked fine for us, although naturally the seal isn’t as tight as it could be.

The main YKK zipper has an internal stormflap to seal out the cold and a zipper “garage” at the top to house the zipper – but it’s only a one-way zipper, so you can’t vent from below. The hood is well-shaped with an elasticated rim, but the peak is not wired or malleable to a shape you desire. The fit of the hood is adjustable via a drawcord at the rear, and a little tab of fabric with two popper buttons enables you to roll away and secure the hood when desired.

Another nice feature is that the entire jacket can be stuffed into the right-side handwarmer pocket, and then zipped up to form a neat, compact little package sized 23cm x 15cm x 10cm. It’s about the size of a small handbag, and is an excellent way to store the jacket in your backpack. The zipped-up storage bag has two little carabiner carry loops, meaning you can hang the bag on your backpack or harness for easy access.

Verdict

A high-tech softshell with good features and an incredibly low weight – but it’s pricey

About the author

James Forrest is a prolific peak bagger and long-distance walker who’s one of the most high-profile outdoor writers in the UK. He writes regular features and route guides for Trail and has been one of our main gear testers for the last few years. James is based on the edge of the Lake District so when he isn’t off on his latest crazy adventure or challenge, he’s walking in his local fells. James reviews every type of outdoor kit for Trail and is a real authority on everything you need for wild camping and packing light for a multi-day walk.

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