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We've tested over 20 of the best bivy sacks through the years and purchased 12 top models for our latest round of side-by-side testing and analysis. Our testers have used them over all sorts of terrain - hanging off the sides of cliffs, basking in mountain meadows, and in riverside campsites in the desert. We waited out surprise storms at high camps and took them along on climbing, camping, bikepacking, and ultralight backpacking missions. With our field tests complemented by objective comparisons, we rate each product using key metrics. If you're looking for a great deal when it comes to weather protection, we've got the best choices for you to consider.
The Outdoor Research Helium Bivy offers fantastic weather protection, comfort, ventilation, and breathability, all in a relatively lightweight package. While other models might offer high performance in just one or two areas, the Helium is a true all arounder. It performed way above average in most of the metrics we tested, and its overall score was higher than any other bivy sack during our testing process. Not only is it packed with features, but the entire package comes in at about one pound, pole included. Put simply, it combines everything we want in a bivy better than any other product we've tested.
While we are thoroughly impressed with this bivy, we'll do our best to be objective and point out its flaws. Right off the bat, it's important to know that if you're looking for the burliest and most durable of bivy bags, this isn't it. The OR Helium is intentionally designed to be a lighter-duty version of heavier-duty and more protective alpine bivy sacks. In a perfect world, you would have a different and specialized bivy for every situation. In the real world, you're probably limited to one, and the OR Helium bivy performed excellently in every situation we threw at it, from heavy rain to not weighing down our pack for extended outings.
The Sierra Designs Backcountry Bivy is a past favorite and proved once again that it's an effective and functional bivy for a wide variety of situations. Although it isn't the lightest or most weatherproof, it offers features found only in the heavy-duty models, such as a bug screen and an inventive way to prop up the face of the bivy, giving a nice bit of breathing room to the occupant. It's not as comfortable as the OR Helium, but it's close, and the Backcountry Bivy weighs less, which is a bonus.
While we didn't find much to complain about while testing the Backcountry Bivy, there is a point worth mentioning – the zippers are not as weatherproof as some models. Depending on the type of camping you're planning to do with your bivy, this may not hold much importance, but some leaky seams in a rainstorm could make the difference between dry comfort or a sad, soggy night. Despite this flaw, if you're looking for a top-tier bivy sack that is substantially cheaper than the most expensive models, this is the one.
Probably not long enough if you're over six feet tall
The Outdoor Research Alpine AscentShell bivy sack is an extremely weather-resistant bivy sack designed to deflect all of nature's elements in the alpine environment. It performed really well during our testing, scoring highly in all of our metrics. And at just under 20 ounces, it's only a few ounces heavier than many of our top-scoring models. We were very impressed with how packable the Alpine AscentShell is, especially considering its burly construction and high performance resisting rain, wind, and snow. The side zipper has smooth action and allows ease of entry and exit while ventilating moisture.
While the OR Alpine AscentShell offers top-notch protection from the elements, our team found that the tightly woven fabric isn't super breathable in favorable conditions. If you are taller, this model may not quite be long enough for you. One of the more expensive products in our lineup, it's important for you to consider if the high quality of this bivy sack is worth the high cost. Drawbacks aside, the AscentShell is our top recommendation for inclement weather.
The MSR Pro Bivy comes out on top in the weight-to-protection ratio. Weighing in at an impressive 8.9 ounces, the MSR Pro is a fantastic solution for those looking to add an insurance policy to their exposed ridge scramble or ultralight overnight. On the surface, this bivy appears to be something to reserve just for the unexpected emergent rain shower. Still, depending on your tolerance for discomfort, this could serve as an extremely lightweight shelter for longer excursions.
The Pro Bivy is more of a specialized tool rather than an all-arounder. If you need a bivy that can withstand a big storm, check out the Sierra Designs Backcountry or the Outdoor Research Helium. If you're in the market for a bivy strictly for emergencies, the SOL Escape is our favorite. However, as an emergency shelter or for ultralight missions into the hills, we think the waterproof fabric, ample footprint, and ease of setup make this model a welcome companion.
The SOL Escape Bivy is a remarkable and simple emergency bivy. We have used ours on and off for over a year, and it has held up well, which is asking a lot from an inexpensive emergency bivy. If you're on a budget and want to ensure you have a little extra warmth and protection in your pack, the SOL Escape is a good choice. If we recommended a bivy solely upon its price-to-performance ratio, this might be the highest-rated bivy we have ever tested. The proprietary "metalized spun-bonded olefin" fabric proved to be lightweight, very weather-resistant, breathable, and added a significant amount of warmth to the 35-degree sleeping bag that we used during testing.
If you're venturing into a cold and dry climate, you could certainly get by with the SOL Escape as your primary shelter. However, the footprint is far too small unless you're under 5'11" and 175 pounds, and this model can't be fully closed. While the SOL Escape is certainly a far cry from the premium bivys, like the Outdoor Research Helium, it is an excellent emergency shelter that can be used over and over without losing the attributes that make it so functional.
We consideresd over 40 different models during our research process before buying the top 12 contenders to put to the test for this review. We examined how well they protected us from wind and precipitation and how they vented and transferred moisture from inside to out. We also paid attention to packed size, weight, comfort, and compatibility with other items. Testing was conducted in the field, in various environments, from swampy conditions to snow, to rocky ledges. This review is the distilled knowledge we gained from multiple seasons of intensive testing, and we hope it will serve you well in your own selection process.
Our bivy sack testing is divided across five different metrics:
Weather Resistance (25% of total score weighting)
Weight (25% weighting)
Comfort (20% weighting)
Ventilation (15% weighting)
Packed Size (15% weighting)
This review is brought to you by OutdoorGearLab Review Editors and multi-discipline outdoor athletes Brian Martin and Brian Smith. As a former member of Yosemite Search and Rescue, Brian Martin was tasked with researching, testing, and replacing team equipment. This, in addition to his lifestyle centered around various outdoor pursuits, gives him a keen understanding of the features to look for in all kinds of outdoor equipment. He's as familiar with rock climbing as he is with backpacking or mountain biking, and he brings this broad experience to help readers discern the advantages and disadvantages of different products for different pursuits. Brian Smith is a certified IFMGA/AMGA American Mountain Guide based in Jackson Hole, Wyoming, and spends multiple nights per year camped out in the snow, in the desert, or at a bivy site on the side of a mountain. Whether guiding skiing, rock climbing, ice climbing, or alpine climbing, Brian uses outdoor gear more frequently than most human beings on the planet. His keen eye for detail lets him catch mistakes before they happen in the mountains as well as recognize high-quality gear that facilitates having memorable experiences in the outdoors.
Analysis and Test Results
Whether or not to bring a bivy depends on many factors, and everything from weight to the weather forecast to the available space in your pack can influence the decision. Before purchasing a bivy sack, consider the conditions in which you will use it. The high mountains in winter? A boggy swamp in spring? Each of our reviewed products has unique characteristics that might create a compelling reason to consider it for your next outing.
We aim to bring you the best of the best, but also the highest value, especially when it comes to performance and cost. Our team of experts put each model through a series of tests, awarding scores for a series of metrics. Determining which bivy will suit your needs will certainly involve a list of pros and cons. What are you looking for? If the best value tops your chart, look for the highest-performing product from our scores that fits your price range. The Sierra Designs Backcountry Bivy, for example, covers what most folks need from such a product (low weight, comfortable, and weather-resistant) without costing as much as most premium models. Or for emergency protection on a budget, the SOL Escape Bivy offers the extra protection and warmth you might need when the unexpected occurs but also doesn't put you out a ton of cash. As always, we recommend finding the product that fits your performance needs and financial limitations.
From emergency bivys to the ultra-protective alpine expedition models, it's important to have a firm understanding of the characteristics of the bivy you're considering. Does it make sense to have an ultralight emergency bivy as well as an alpine heavyweight? Whatever your needs are, we thoroughly tested each of these bivy sacks within their intended boundaries (and beyond) to know where their limits really are. Waterproof fabrics and the ability to fully zip and enclose the sacks are a couple of key performance considerations.
The most weather-resistant bivy sacks we tested were the Outdoor Research Alpine AscentShell, the Outdoor Research Helium, and the Black Diamond Bipod. All of these options were fantastically waterproof and offered substantial protection from the elements. In our opinion, these models provide the best balance of durability, warmth, and overall protection. Conversely, in our shower test, the Rab Ridge Raider Bivi let water in through the floor of the sack, so we do not recommend this model for any type of wet conditions.
Different types of fabrics work best in different situations. A fully waterproof material, like Gore-Tex, will keep all the rain out, but even the most breathable fabrics have a hard time letting water vapor from sweat and breathing escape. Ripstop nylon is lightweight and waterproof, if treated with a durable water-repellent (DWR) coating. It's typically more breathable, but it's only ideal for a light rain since it isn't entirely waterproof. The SOL Escape deviated from the norm by constructing a bivy from metalized spun-bonded olefin, which is typically used as a moisture barrier for home construction. This material provided excellent weather resistance while maintaining some breathability. However, because this option doesn't close all the way, its protection from the elements is minimal.
Some bivy sacks are made for four-season protection and can be used in wintry, alpine conditions. Other models strive to save weight and don't allow for a complete closure of the waterproof shell material around the face, so they're best reserved for emergencies or milder rain and temps. The least protective are also often the lightest options. Just because they can't keep you warm and dry in a heavy downpour doesn't mean they don't have their place. These lightweight emergency bivys can be worth their weight in gold for fast and light ascents, long trail runs, or fastpacking when some extra protection is warranted.
Like all camping shelters, the way they're used can affect weather resistance. When possible, selecting higher ground or a clearing under a tree will add a bit of extra weather protection and avoid pooling water in a nasty deluge. Always check the trees overhead for dead limbs or "widow-makers," which can break off dangerously (especially in a storm).
When hunting for a bivy sack, it's important to take a mindful moment to imagine what exactly you're going to be using it for. Before you look at weights and packed size, make sure the bivy will perform at the level you need it to. If you're venturing into a snowy alpine environment with likely precipitation, you want something you can comfortably spend a lot of time in and that you are confident will keep you dry. If you're heading out on a burly all-day ridge climb but aren't sure if you will have to bivouac, a lightweight emergency option might be more appropriate.
If you're breaking into the ultralight game, there are some excellent options available that offer decent protection against those surprise rain showers or windy nights. The lightest reusable bivy is the SOL Escape. Most bivy sacks weigh under two pounds and are far lighter than our favorite backpacking tents. Our top recommendation overall, the OR Helium, weighs just over a pound. If you are willing to add a bit of weight to increase weather resistance, the OR Alpine AscentShell is roughly 20 ounces, which is much lighter than several models that fell short in our inclement weather tests. Keep in mind, though, that there are some ultralight tents that contest some of the heavier bivy sacks, and they're much more spacious.
Comfort is always an important criterion for outdoor gear, especially for gear that you rely on for shelter in backcountry situations. Time spent in an uncomfortable or cramped bivy with creepy crawlies getting inside can turn a user away from bivy sacks for good. Contributing factors to each bivy's comfort rating include insect protection, roominess (volume and floor plan), ease of use, and added features, such as gear pockets or straps to hold your sleeping pad in place.
If you choose a bivy because you want a shelter that weighs less and takes up minimal space in your pack, you should expect less space for you inside — just hopefully not to the point of discomfort. We compared floor space, head space, and shoulder width when assessing our comfort ratings. The OR Helium and OR Alpine AscentShell earned the top scores for this section of our assessment. Both employ a singular pole that allows for extra breathing room and even enough space to read a book.
Ultralight and minimalist models can often be less spacious to cut down on the amount of material used. Conversely, four-season models often have wire hoops or tent poles to help increase volume, leave room for the face, and provide an experience very similar to sleeping under the stars with all the protection of a tent. The Sierra Designs Backcountry Bivy is an excellent combination of size and comfort features, such as the ability to keep the ceiling away from your face with no added weight. The SOL Escape is on the snug side but still usable for our 5'11" gear tester.
Ventilation in bivy sacks can be a tricky thing. Like any piece of waterproof gear, typically, the better a sack protects you from rain and weather, the less it breathes. How well a bivy ventilates and how much condensation builds up inside is a huge factor in its versatility and performance.
Many human factors can make your night miserable even in an exceptional bivy, so here are a few actions you can employ to make sure your bivy will perform to its highest abilities. The main issue is that your condensed breath or extra sweat from getting overheated can build up inside the sack, causing a "rain" effect when moving or shifting inside. One of the easiest things to do to prevent condensation if you have dry weather is to keep the zippers open as much as possible. Even during downpours or extended periods where complete protection is necessary, we recommend "cracking" the mesh or zipper to allow some ventilation of the condensed air inside.
If dry weather is not in the forecast, the two critical things to keep in mind are to make sure your breath is directed toward the outside of the sack and to use a sleeping bag and pajamas (or whatever clothing you sleep in, if any) that are the appropriate warmth for the temps. If the temps are variable, or you toss and turn in your sleep (and can't easily ensure your mouth stays at the bivy opening), it might be a good idea to bring a synthetic sleeping bag instead of a down sleeping bag. Why? Synthetic insulation will retain its insulating properties and keep you warm if it gets damp or even soaked.
If your bivy can be staked out or has a pole to give you space around the head, taking advantage of these features will add extra air space between your body and the bivy walls, which significantly improves its ability to ventilate. The Outdoor Research Helium and the Outdoor Research Alpine AscentShell both have this feature, making them more comfortable than models that let the fabric rest against your face.
No matter what you intend to do with your bivy, packed size is important. Space in our haul bags, backpacks, and bike bags is always at a premium. Having a bivy that is lightweight and can be crammed into a tiny package is essential. By dropping down from a tent to a smaller bivy, you should be able to save several liters of space, allowing for a smaller pack overall or room for other essential gear. Taking this even further, if you opt for an ultralight bivy, you might even be able to pack it down to the size of a soda can, saving loads of space in your pack.
We measured each product when packed up in its (usually provided) stuff sack. Some models have poles that could be added to the same stuff sack or stored in your pack separately. The Survival Frog Tact Bivvy 2.0 offers the smallest packed size of all the products tested (2" x 4.5"), but it's more of a single-use bivy because it can be easily torn and rendered useless (think giant yard leaf bag). A much more durable and highly affordable model, the Sierra Designs Backcountry Bivy, measures 3" x 9.5". Lastly, the top-tier high-high performance OR Helium and OR Alpine AscentShell measure 4" x 12.5" and 3.5" x 12.25", respectively.
Climbers, mountaineers, and ultralight backpackers alike may be interested in a bivy sack for numerous reasons. In addition to being a lightweight emergency shelter, these products can be a lower-weight and smaller alternative to a tent. A bivy's smaller footprint can also allow you to sleep in a multitude of places where a traditional tent would not be possible. Many factors need to be considered when selecting a bivy, ranging from weather resistance to pack size.
GearLab is founded on the principle of honest, objective, reviews. Our experts test thousands of products each year using thoughtful test plans that bring out key performance differences between competing products. And, to assure complete independence, we buy all the products we test ourselves. No cherry-picked units sent by manufacturers. No sponsored content. No ads. Just real, honest, side-by-side testing and comparison.