Outdoor Research Alpine AscentShell Bivy Review

The Outdoor Research Alpine AscentShell bivy sack has top-notch weather resistance that makes it stand out from the competition. Our testers were impressed with its ability to effortlessly shed water and snow, the long side zipper that made it so much easier to get in and out of, and its roomy hood. We were also very surprised by how lightweight it was, even with those added features.

Performance Comparison

Weather Resistance

The Alpine AscentShell was designed to perform in the mountain environment. Its fabric is extremely resistant to rain and snow. In fact, we tested it in the shower, full flow, for one and a half minutes, after which the 10-year-old daughter of our lead tester emerged bone dry and smiling.

How can this bivy sack shed water so easily, you might ask yourself? The answer is in the trademarked fabric. The AscentShell technology spins fabric into three layers that resist moisture, breathes "relatively" well, and even stretches. All of this, and the fabric is still lightweight – the perfect recipe for a bivy sack.

Weight

If a bivy sack is heavy, then it defeats its own purpose. That is not the case with the Alpine AscentShell. Weighing in at 19.9 ounces, we simply couldn't quite comprehend how light this bivy sack was with a side zip and roomy hood. Please keep in mind as you look at the chart below that extremely lightweight bivy sacks might sacrifice vitally important features, like weather resistance.

The fabric technology helps save weight. Zippers and zipper pulls are just the right size. The hood pole is in the featherweight category. The stuff sack weighs almost nothing. So, there you have it, lightweight.

Comfort

It is certainly more comfortable and easier to get into a bivy sack with a side zipper, which the Alpine AscentShell has. And, the hood is relatively spacious, for a bivy sack, of course. Relative is a key word here – you will always sacrifice some comfort using a bivy sack versus a tent. But your pack will be lighter, which adds comfort, right?

A bivy sack with stretchy fabric is more comfortable because if you shift around inside while sleeping, the bivy sack material is more flexible and moves with you. The AscentShell fabric stretches, but not as much as the OR Helium's Pertex fabric, so it's not quite as comfortable as the Helium.

Ventilation

With more resistance to moisture comes less breathability, even with innovative advances in material technology. The AscentShell fabric is more tightly woven, which repels moisture better, but this makes it less stretchy and less breathable. Fortunately, the side zipper is designed to help with ventilation and has a velcro tab to partially close the zippered opening while maintaining airflow.

The good news is, the choice is easy: do you want a more stretchy and breathable bivy sack, or one more resistant to foul weather? If the latter is your choice, the OR Alpine AscentShell is the way to go.

Packed Size

The stuff sack for the Alpine AscentShell is the same size as the Helium's stuff sack. However, since the material is thicker and stiffer, it fills the stuff sack up more and doesn't pack as small. That said, we were still impressed with how small the packed size was, with room to spare inside the stuff sack.

While the pole is pretty easy to insert into the hood, it is somewhat difficult to remove. You just need to inchworm it out by pushing on the far end while scrunching the fabric as you push it through. The durable, weather-resistant material makes this process a bit more challenging than removing the pole from the OR Helium, which has softer, more supple material.

Should You Buy the Outdoor Research Alpine AscentShell?

If you find yourself venturing into the high peaks or stormy climates and you want to shave some weight and space in your pack, the OR Alpine AscentShell bivy may be the right choice. It is one of the more expensive bivy sacks in our lineup, so you might consider if the cost is worth the added benefit for your outdoor pursuits. The durable material and tightly woven fabric are designed to hold up to inclement weather, all in a tight and relatively light package.

What Other Bivy Sacks Should You Consider?

Interested in less-expensive, lighter, or smaller bivy sacks? If you're looking for a top-notch, lightweight, weatherproof bivy, check out the Outdoor Research Helium Bivy. If you're searching for an emergency bivy sack or an ultralight bivy sack limited to dry and/or cold climates, take a look at the SOL Escape Bivvy. Whichever bivy sack you choose, we hope this review has helped you find what you're looking for in a simple shelter to suit your adventures.