The Alpine proved to be a strong contender for storm protection at the cost of catering to those looking for a more comfort oriented bivy.
Throughout the testing period, we encountered several types of weather and precipitation from snow and wind to warmer periods of rain. There were several situations where the Rab Alpine performed well and a few that we found ourselves feeling a little too miserable. During periods of cold blowing snow, the Rab model performed well. If you're looking for a bivy with excellent weather protection without sacrificing comfort and usability, check out the Outdoor Research Helium Bivy.
The waterproof fabric and simple bathtub floor design kept us shielded both from blowing snow and ground snowmelt. The downside of the simple design rears its head in warmer rainy climates. The only way to create any ventilation while it's raining is to unzip the opening and use the fiddly velcro closures. Not only is this process tedious when it's raining, but it doesn't ventilate very well. When we found ourselves holed up in the bivy for a night of rainy yet warmer weather, we were saturated in the morning. The condensation from our body didn't vent, and the velcro closure had allowed water to blow in.
Getting the Velcro lip fastened from inside before you zipped up the bivy was a chore.
One of our biggest issues with the Alpine was the lack of ventilation. There is no bug netting and no easy way to reliably ventilate this bivy sack. If you're looking for a bivy that retains similar weatherproof qualities and offers better ventilation options, we like the Outdoor Research Helium or the Sierra Designs Backcountry Bivy. Both of these competitors offer highly water resistant models that also allow for adequate ventilation in a variety of weather conditions.
The one climate the Alpine from Rab functioned flawlessly was in cold, windy, and snowy conditions. We could have the zipper unzipped just enough to allow the wind to circulate air but not so much snow/water would blow in. If you're buying a bivy primarily for colder alpine conditions and just want something that will keep you dry, this could be a pretty good option for you.
The Rab's ventilation system consisted of unzipping and using the velcro tabs. When we would toss and turn, the velcro would come undone.
Through the testing process, we found all of the models we tested fit nicely into three different comfort categories. Emergency bivys were suitable for a night or two of use out of absolute necessity. Minimalist models were suitable for several days of planned bivuacing, and expedition bivys were suitable for extended expeditions where comfort was critical for success. The Alpine from Rab fit nicely into the minimalist category. If comfort is an absolute necessity, we'd recommend the Outdoor Research Alpine or the Sierra Designs Backcountry Bivy.
The Alpine from Rab is simple. There is no way to elevate the ceiling away from your body, and the zipper/Velcro closure was consistently frustrating. All that being said, there was ample space inside for our tall gear tester, Z-Rest sleeping pad, and lofty down bag. We didn't find the bivy to be either too large leaving dead space, or too snug and constricting. All in all, the Alpine was comfortable though we wouldn't want to be married to it for ten days in the backcountry.
Of the minimalist style bivys, the Rab was one of the most generous on space. When never felt cramped or restricted even when it was fully sealed up.
Once again the Alpine lands right in the middle of the pack. At about one pound or 457 grams, the Rab isn't exactly a heavyweight. Because the creature features were cut out of this bivy, Rab was able to use three-layer 70D coated nylon to create the waterproof bathtub floor as opposed to the ~30 denier fabrics of comparable models in this review.
While this cut out some of the comfort factors when the ground was wet, or weather turned for the worse, it made a noticeable difference. If you don't want to sacrifice comfort and value shaving off some grams, check out the Sierra Designs Backcountry Bivy as it is only 13.6 ounces and retains some excellent comfort features.
Considering the thicker more weather resistant material of the Alpine, 16.12 ounces isn't too bad.
Packed, this bivy is a reasonable 4x10 inches. Small enough to disappear into most small backpacks. If space saving is critical, the MSR Pro Bivy has similar performance to the Alpine but packs down into a tighter, smaller stuff sack. Considering the thicker, more durable and waterproof fabric of the Rab it does pack down quite well.
The other contenders in this review that have 70D+ fabric, the Outdoor Research Alpine and the Black Diamond Bipod both have a packed size that almost doubles the Alpine from Rab. While the Rab isn't quite as comfortable, it does save a lot of weight and room in the pack over the heavyweights.
This model is a strong contender for light and fast alpine missions. Staying shielded and dry in cold environments when it's probable you will be bivyed out in a snow cave or on wet ground are what this bivy is designed for. If you're looking for a bag that can "do it all" we like the Sierra Designs Backcountry Bivy or the Outdoor Research Alpine as they are both suited for many climates and retain excellent weather resistance. If you like the idea of a minimalist bivy and don't need the 70D protection of the Alpine we were huge fans of the SOL Escape as it weighs a fraction of the Rab model but does an excellent job in extended emergency type situations.
Our biggest struggle with the Alpine was the price tag. At the list price of $275, there are simply so many options that outperform it that we couldn't recommend getting this bivy. That's not to say it wasn't excellent in performance, only that bags such as the Outdoor Research Alpine and Sierra Designs Backcountry Bivy are cheaper, offer the same weather resistance, and infinitely more comfort/features.
The Rab Alpine Bivy is a great bivy sack offering fantastic cold weather/storm protection. It was roomy and comfortable but had a few drawbacks. The zipper/velcro closure system was pretty frustrating, especially with cold hands. We also feel like the price is on the extreme high end for what this bivy offers.