RAB Alpine Bivi: goodbye false modesty and brooding looks

Rudy Testa February 2, 2025

What glory is there left in sleeping under the stars when a bivi bag offers protection from the elements as reliable as a tent, at a ridiculous weight of 470g and takes up less space than a water bottle?

The Alpine Bivi from Rab is available, and with it, the end of your fellow travellers' admiring sighs when you used to boast about facing the night without your tent.

It's all about the construction...

The Alpine Bivi is cleverly made from two different fabrics to avoid unnecessary weight: the upper section is made from 3-layer eVent, a waterproof-breathable fabric used in the finest waterproof jackets, while the lower section is made from a 70-denier coated nylon fabric (the same as the floor of your tent). This is smart design, since your sleeping bag needs to evacuate the perspiration you produce during sleep — eVent is only used for the upper section, the part that can actually allow your sleep system to breathe.

For the lower section, the choice of a coated fabric that is lighter and more robust than eVent also makes sense: it ensures perfect waterproofing on the ground, doesn't need to be breathable (since your body, pressed against the ground, would prevent moisture transfer to the outside) and guarantees greater longevity than a bivi bag constructed entirely from a waterproof-breathable fabric.

...but also a matter of comfort

Generous in its dimensions, you also have the option of placing your sleeping mat (even an inflatable one) inside if you're a restless sleeper (no "mummy bag effect" upon waking); and if weather conditions lead you to fear heavy water runoff, simply place the mat outside to limit contact with water.

If you prefer to place the mat inside, it is nonetheless advisable, as you would with your tent, to protect the floor of your bivi bag by placing a sheet of Polycree, Tyvek or another waterproof and durable fabric between the ground and the bivi (= bivi bag); this will significantly increase the lifespan of your bivi bag's floor, for only a few extra tens of grams.

Although the Alpine Bivi can accommodate sleeping bags with considerable loft, it may be preferable to keep the inflatable mat outside the bivi bag when used with very warm sleeping bags (from -15/-20°) to ensure that the down in your bag is not compressed by the bivi. Finally, it will also accommodate "larger builds" (up to 190/195cm).

Let's be honest, comfort is all relative

Depending on your favourite regions, altitude and season, you might prefer the little brother of the Alpine Bivi: the Ascent Bivi which, while retaining the same geometry, incorporates an insect-proof mesh. However, the younger sibling weighs in at 625g, that's 155g more than the Alpine Bivi, and at that weight, the advantages of a bivi come into direct competition with those of an ultralight tent.

Because while the reduced weight of a bivi will allow you to make even more of your days on the trail, there are still a few concessions to be made regarding comfort: changing clothes in a bivi is a luxury only a few yogis can afford, and you'll quickly realise it's far simpler to get changed behind a tree, a rock, etc.

Also, if you can't fall asleep without your usual 30 minutes of reading, the bivi might not be the most sensible choice. As you'll have gathered, a bivi bag is a shelter whose sole function is to ensure...sleep! If conditions are favourable, nothing stops you from playing a hand of poker with your fellow travellers (with a mountain view, no less!), but if bad weather rolls in, the priority will be to batten down the hatches...

Main objective: set up quickly and efficiently

Finally, one of the last advantages of the bivi over the tent is its ease of setup. And this is no minor point! With a bivi bag, you no longer need to worry about finding the ideal spot to pitch your tent (relatively flat, not too rocky, discreet enough without ending up in the undergrowth...): you can set up discreetly and quickly almost anywhere! In 4 minutes your bed is ready, and packing up your sleep system will take barely any longer in the morning! Wake up, roll up your bivi bag, sleeping bag and mat and move straight on to the morning coffee stage: in 20 minutes, you'll already be back on the trail...

With the Alpine Bivi, bivi bag bivouacking is no longer the preserve of the most seasoned hikers — those who can make do with next to nothing and endure anything. So, to leave your companions speechless with admiration once again, you'll need to seek adventure a little further afield...or master Stairway to Heaven by Led Zeppelin on acoustic guitar.