Cimalp Whymper Technical Fleece Jacket: a mountain midlayer par excellence

London-born Edward Whymper was a leading figure of the Golden Age of Alpinism. Indeed, it was his fateful first ascent of the Matterhorn in 1865 that brought about the end of this period, a time when the great peaks of the Alps were first climbed, often by wealthy Brits expertly guided by locals. The Matterhorn would be the most enduring event in Whymper’s legacy, yet he was a truly pioneering early proponent of alpinism, one of Britain’s greatest ever mountaineers, with many impressive feats to his name.

French brand Cimalp clearly holds Whymper with enough regard to have named one of its best-selling technical fleece jackets after him. It’s designed as a mid-layer that’s “perfect for shifting mountain conditions, climbing or trekking activities” and is available in both men’s and women’s versions. Cimalp namechecked mountaineering, climbing and ski touring as it’s ideal uses, though I had a suspicion it’d be a good option for pretty much all outdoor pursuits.

I’ve tested half a dozen pieces of Cimalp kit over the last few years and was stoked to try out this high-performance mid-layer during my mountain jaunts. Allez!

First impressions

The Whymper is very similar in terms of design, features and function to Berghaus’ MTN Guide MW Hoody, a mid-layer that's part of the British brand's premium Extrem range for mountain professionals. The Whymper is obviously tailored towards active use in the mountains, with a pair of front chest pockets that are higher than you’d get on a standard hooded jacket. This is to enable the wearer to still have access to the pockets while wearing a harness.

The most obvious feature, as with the Berghaus hoody, is the design of the main fabric. Turn the hoody inside out and its grid-like structure becomes immediately apparent, comprising thousands of rectangular cuts of fleece, much like Polartec's Power Grid design. In this case, it's Cimalp’s Cimagrid, a design intended to provide both warmth and breathability for strenuous outdoor pursuits. The fleece cubes insulate while the gaps between them breathe – simple but effective.

The fit is athletic but not restrictive, ideal for a layer that’ll spend much of its time beneath a waterproof jacket. Partly thanks to this fit, it looks good too. I was testing the Noir-Gris colorway, which has subtle red detailing along the zippers and grey breast sections. I certainly felt great wearing it and I also reckon it represents decent value when compared to the direct competition.

The Whymper is also available in a range of other colors: Blue, Purple, Black, Blue / Green and Green / Yellow for men; and Black, Green, Blue and Purple / Pink for women.

Cimagrid breathable insulation

The feature that elevates the Whymper above your standard mid-layer is its grid-like fleece structure – named Cimagrid. The idea is that the gaps between the tiny, rectangular polyester fleece sections allow the jacket to breathe, thus allowing radiated body heat to escape, wicking moisture away and keeping you cool during dynamic activities. At the same time, the blocks of fleece insulate, keeping you warm at the same time. It’s not quite as dramatic design as the sieve-like face fabric of the Houdini Pace Flow Houdi, but it’s a similar idea.

It's this feature that makes the Whymper so well suited to pursuits where temperature regulation is key. As a mid-layer, it allows warm, moist air to move through the system, continuing the good work of your moisture-wicking base layer.

Another key quality of this fabric is its 6% elastane content, which enables 4-way stretch, meaning the garment is flexible both horizontally and vertically. This is crucial when it comes to the freedom of movement needed for activities like alpinism or skiing, especially given the hoody’s tight fit. Meanwhile, the grid structure also means less weight and greater packability, both big pluses for long adventures in the mountains.

Unfortunately, unlike with the Berghaus equivalent, there’s no mention of recycled materials here, or the jacket’s recyclability at the end of its life. However, Cimalp mostly sources its dyes and pigments from biological sources, its clothing is completely PFC free and its fabrics are always either Bluesign or Oeko-Tex certified – so the brand are making some strides towards a sustainable future.

Other features

As mentioned, the Whymper boasts two large, zippered chest pockets, placed high enough for access when wearing a climbing harness. Both these and the central full-length zipper boast chunky branded pulls for ease of manipulation when wearing hiking gloves. The zippers on the pockets slide up and down with consummate ease, while the central zipper feels slightly more rugged – reassuringly so. Beneath the central zipper is a fabric overlay that stops heat from escaping through this potential area of weakness. Little features like this are very welcome and nod towards the jacket's thoughtful design.

When fully zipped up, the Whymper provides coverage around the neck, a nice touch that provides additional warmth during colder adventures.

The hem and cuffs aren’t adjustable, using elastic rather than drawstrings or Velcro. This isn’t an issue, as they wrap nice and tight, and are easy to loosen with a pull. By keeping things simple, Cimalp have kept weight to a minimum. Likewise, there’s no adjustability in the hood, which sits snug around the head when the front zipper is fully done up. Despite this, its elastane content means that it will take a helmet without any problems.

On the trails

I’ve been wearing the Whymper in the mountains for several months, both as a mid-layer during winter adventures – paired with the excellent Cimalp Cosmiques H Breathable Trekking Jacket – and as an outer on spring and summer exploits in Wales' Eryri (Snowdonia) National Park and for everyday wear around England's southwest.

On a wintry week in Scotland’s Cairngorms National Park, the Whymper was put through its paces during long mountaineering days spent climbing some of Scotland's highest mountains. The Highlands are renowned for their long walk ins, and I found the Whymper was a great choice for these. It provided the additional warmth I needed while effectively regulating my temperature during these strenuous treks. Whenever I needed to dump heat during an ascent, I’d simply open the front zip and let things cool off.

Once up high, the waterproof Cosmiques Jacket was deployed over the top and – in the best way possible – I didn’t notice the Whymper at all. This is a good thing – it means it was doing its job successfully as the meat between my outer and my base layer. The athletic cut meant that my jacket fitted on top of it without issue and I had no qualms with the hoody’s freedom of movement.

For warmer season adventures, the Whymper’s low weight and packability are a boon, as it’ll undoubtedly spend as much – if not more – time scrunched into a daypack as it will on your torso. I encountered mild conditions that really put its breathability to the test and it passed with flying colors. It helped me to regulate my temperature more effectively than a standard, thicker fleece would have.

At the end of the day, it’s down to the wearer to choose when to wear it, when to leave the front zip open and when to stash the jacket away. The upshot is that, for a hiking mid-layer, it does everything that’s asked of it.

When it comes to wind resistance, it’s not as effective as a bulkier fleece. This is the obvious compromise when it comes to breathability. I found that strong wintry gusts would penetrate the grid structure when the hoody was worn as an outer. However, as a mid-layer, it’d usually be paired with a wind-blocking softshell or an even more rugged waterproof jacket, so it’s not a big issue.

Being a technical mountain hoody, it’s perhaps not as suited to everyday walks as a standard fleece jacket. There are no handwarmer pockets here for those casual winter ambles and, as mentioned above, it’ll let wind through more readily than some. That’s not to say I didn’t enjoy wearing it for the everyday, it’s just that it’s more geared towards technical use.

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