New for 2014, the Berghaus VapourLight Hypertherm Reversible Jacket is a unique, and versatile, synthetically-filled mid-layer that weighs just 167g in a men’s medium and packs down small enough to stash in a moderately sized stuff pocket.

But that’s just the start of it, there is clever stuff going on here that means the jacket, designed with Berghaus athlete and mega-runner Philippe Gatta, is extraordinarily versatile if you’re a lightweight runner, backpacker or cyclist and possibly even for climbers.

Tech Stuff

Not only is the Hypertherm super light, it’s also reversible with different fabrics on each side. The blue side is made of wind resistant AF™ shell and while it’s not 100% windproof, it still does a good job of keeping the chill out, without sacrificing too much breathability.

The other side, the red one, is made of a more loosely woven, more permeable fabric. It provides less wind protection than the blue, side, but breathes better.

The idea is that when it’s proper cold and your priority is staying warm, you wear the blue side outwards, holding more warm air inside the insulation and reducing wind chill. Conversely, if you’re getting hot, use the jacket with the red side outwards to allow more air permeability and lose heat more easily. Or that’s the theory.

Performance

Don’t get the Hypertherm confused with more conventional synthetic insulation jackets, even something like the original Rab Xenon is quite featured compared to this – it really is a pared-downm minimalist bit of kit, which is why it weighs just 167g.

There are no pockets – well, one tiny one with the care label inside – no hood, the cut is short and close and hem and cuffs are lightweight Lycra bound. It’s not a luxuriating in the pub sort of thing. Or even a snug in the tent one.

What’s it’s made for, is being tiny enough to stash in the smallest bum-bag or race pack and then adding just enough extra warmth without being overly sweaty in the process, so you can wear it on the move.

And that, pretty much is what it does. The tiny pack size means you can chuck it in where other insulation simply wouldn’t fit. But when you do need it, it’s surprisingly effective. We found you could either use it alone over a baselayer top as a sort of lightly insulated windproof in cold conditions or as a warmish mid-layer under a waterproof shell like the sub-100g Berghaus Hyper Smock.

When you’re on the move and chucking out the watts, there’s enough insulation value in there to keep you comfortably warm. And the clever bit is that if ‘comfortably warm’ starts to become ‘uncomfortably hot’, you can simple take the jacket off, turn it inside out and carry on.

We were a little skeptical initially, but the reversible fabric thing really does work, it’s like having two jackets in one with an appreciable performance difference between the sides. And if you get too hot again, no problem, take it off and stash it. That’s if venting via the main zip and rolling up the sleeves don’t do the trick.

The fill, by the way, seems typically tolerant of a bit dampness either from inside or out.

Stuff we’d change? A hooded version might be interesting, though it would add a few grammes and be potentially flap happy when not in use.

Verdict

We genuinely think that the Berghaus Hypertherm is a little slice of genius. If it were merely a super-lightweight insulated top, it would impressive enough, but the reversible fabric trick adds a whole new layer of versatility.

It’s not for everyone, you need to accept that the pay-off for the minuscule weight and tiny pack size is a minimalistic design and limited absolute insulation capabilities, but if you’re a fast-moving, hot-running mountain athlete, there’s really nothing else out there that compares.

Combine it with a waterproof Berghaus Hyper Smock and you have a versatile sub-300g waterproof shell and insulation package and that really is quite extraordinary.

Full Specification

• Berghaus Hydroloft synthetic insulation
• Reversible design
• wind resistant AF™ shell one side
• more permeable fabric on the other
• full-length zip with micro-flappage
• elasticated hem and cuffs
• stuff sac supplied
• reflective detail both sides