Bivy Sacks: Part tent, part sleeping bag — pure convenience

A bivy sack or bivy shelter is a bit of a riddle—both sleeping bag and tent, and at the same time not truly either of those things. At its most basic, a bivy is a personal shelter for backcountry hikers, climber or skiers who are more concerned with their objective than they are with spending relaxed time in a tent. It’s a bare-bones, protected place to sleep.A bivy is just larger than a sleeping bag, about the same size and uses tent poles to create a minimalist shelter—in essence, it’s an outer shell for your bag that’s built (usually) with waterproof-breathable fabrics that repel nasty weather. It’s the shelter of choice on alpine climbs, big-wall expeditions, solo through-hikes and other adventures where it just doesn’t make sense to haul a full tent.

Outdoor Research offers a full range of bivys for varied adventures. Just remember that when you shop for one, there will always be a trade-off between features and weight. A light bivy sack will stuff into a small package, but it won’t be as comfortable or protect you as well as a somewhat heavier, bulky model if you get caught in a severe storm. So when you are in the market for a bivy, first decide whether you need a full shelter or simply a rain fly for your sleeping bag. To that end, each one of our bivys offers a range of technical features that correspond to its weight and intended use.

The top of the heap, the 37-ounce Advanced Bivy™ can survive the onslaught of a big-mountain storm. Like an expedition tent, it’s fully seam-sealed and the floor is coated with thick, waterproof nylon. But since you are so close to the ceiling of your bivy, the dome is built with three-layer GORE-TEX® Respiration Positive™ fabric, which breathes even better than Gore’s jacket fabrics and helps conduct condensation from your breath away from your face when you are fully zipped in. It’s more than a dry bag for your sleeping bag, it’s an actual mini tent, complete with two poles and a foot vent.

Also built with GORE-TEX® Respiration Positive™ fabric, the Alpine Bivy™ weighs 30 ounces (seven ounces less than the Advanced Bivy™). But you lose some features when you trade off for the lighter weight and more packable design, since it comes with a single pole and does not have a foot vent.

Built with super-light waterproof/breathable Pertex® Shield fabric, the Highland Bivy™ is very similar to the Alpine Bivy in that it also features a single pole. But, with the added weight savings thanks the fabric, you shed another six ounces. The Highland Bivy™ weighs in at 24 ounces.

If you’re looking for the most packable, minimalist shelter for a fast-and-light objective, the light (22-ounce) Aurora Bivy™ offers GORE-TEX® Respiration Positive™ fabric, but it has no poles at all, and is thus essentially a waterproof cover for your sleeping bag.

For warm climes, where you simply want to keep the insects at bay, the Bug Bivy™ provides a waterproof nylon floor and mesh, no-see-um netting overhead.

Again, the key to buying a bivy is deciding what balance you want to strike between comfort, protection and weight. No matter which route you choose, you’ll be traveling incredibly light without foregoing the safety of shelter.