Best Bivy Sack

Best Overall Bivy Sack

Outdoor Research Helium Bivy

Weight: 16.3 oz | Packed size: 4" x 12.5"

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 OR Helium is a true all arounder. It performed way above average in every metric we tested. Not only is it packed with features but the entire package comes in at about one pound, poles 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. Most importantly is the realization 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 the OR Alpine, and indeed it is. 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.

Read Review: Outdoor Research Helium Bivy

Best Bang for Your Buck

Sierra Designs Backcountry Bivy

Weight: 13.6 oz | Packed size: 3" x 9.5"

The Sierra Designs Backcountry Bivy, a past favorite, 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 does offer 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.

The Backcountry Bivy isn't a bargain choice, but it provides an impressive price to performance ratio. The clever set of features includes a zippered bug screen, the ability to elevate the bivy face without a pole, and a low overall weight make this piece of equipment stand out against the competition and ensure it can compete with some of the more expensive models.

Read Review: Sierra Designs Backcountry Bivy

Best for Ultralight Protection

MSR Pro Bivy

Weight: 8.9 oz | Packed size: 8" x 3.5"

The MSR Pro Bivy comes out on top when it comes to 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, but 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 hold up to a big storm, check out the Outdoor Research Alpine or Outdoor Research Helium. If you're in the market for a bivy strictly for emergencies, the SOL Escape is our favorite. However, if you're looking for something suited for emergencies as well as ultralight missions into the hills, we think the waterproof fabric, ample footprint, and ease of setup on this model make it a welcome companion.

Read Review: MSR Pro Bivy

Best Emergency Bivy on a Shoestring Budget

SOL Escape Bivvy

Weight: 8.36 oz | Packed size: 4" x 7.5"

The SOL Escape Bivy is a remarkable and simple emergency bivy. We have used ours on and off for over a year, and it's held up well, which is asking a lot from an inexpensive emergency bivy. If you're on a budget and want to make sure you have a little extra warmth and protection in your pack, the SOL Escape is a good choice. If we were recommending 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 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. Some of our criticisms include the footprint being far too small unless you're under 5'11" and 175 lbs and the inability to fully close the bivy. 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.

Read Review: SOL Escape Bivy

Why You Should Trust Us

This review is brought to you by OutdoorGearLab Review Editor and multi-discipline outdoor athlete Brian Martin. As a former member of Yosemite Search and Rescue, Brian was tasked with equipment research, testing, and replacement. As a result of this, and a lifestyle centered around a variety of outdoor pursuits, many of which involve spending the night outside in a variety of conditions, Brian has a keen understanding of the finer points in gear. He's as familiar with rock climbing as he is with backpacking or mountain biking, and he brings this familiarity to discern the advantages certain models may have for specific pursuits.

Forty different models were up for consideration before we bought the 8 that are discussed here. We examined how well they protected us from wind and precipitation, as well as 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 a variety of 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.

Related: How We Tested Bivy Sacks

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.

Related: Buying Advice for Bivy Sacks

Value

We aim to not only bring you the best of the best but 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 gives you 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.

Weather Resistance

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? Maybe it makes more sense to have a jack of all trades like the Outdoor Research Helium Bivy. 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.

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 versions 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 since it isn't entirely waterproof, it's only ideal for light rain. 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.

Some bivies 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 most weather resistant bivys in our tests were the Outdoor Research Alpine and Outdoor Research Helium. They were fantastically waterproof and offered substantial protection from the elements. If you want the warmest and most heavy-duty bivy for your next alpine excursion, the aptly named Outdoor Research Alpine is your best bet. In our opinion, it has the most durability, warmth, and overall protection. The Black Diamond Bipod is also an impressive model when it comes to protection from the elements.

The least protective are also often the lightest bivys. 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).

Weight

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 is going to perform at the level you need it to. If you're venturing to a snowy alpine environment with likely precipitation, you want something you can spend a lot of time in comfortably 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. The heaviest is the Bipod, which still weighs under two pounds and is far lighter than a standard backpacking tent.

Comfort

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 bivies for good. The things we considered that contributed to the comfort rating of these each tested bivy included 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.

Does your sack feel like a sarcophagus? While we might have enjoyed sleeping in cupboards or underneath the bed as children, most grown-ups prefer to have some space to toss and turn throughout the night. If you are choosing a bivy because you want a shelter that weighs less and takes up minimal space in your pack, you should also expect less space for you inside. Just hopefully not to the point of discomfort. We compared not only floor space, but headspace and width at the shoulder, when assessing our comfort ratings.

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 useable for our 5'11" gear tester.

Ventilation

Ventilation in bivys can be a tricky thing. Just like any piece of waterproof gear, typically the better a sack protects you from rain and weather, the less it's able to breathe. How well a bivy ventilates and how much condensation builds up inside is a huge factor in its versatility and performance.

There are a lot of human factors that 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 on the inside of 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. Both the Outdoor Research Helium and Alpine have this feature, which also makes them more comfortable than models that let the fabric rest against your face.

Packed Size

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 not only lightweight but can also 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 one of those mini coke cans, saving loads of space in your pack.

We measured each product when packed up in its (usually provided) stuff sack. Some of the models have poles that could be added to the same stuff sack or stored in your pack separately. The TACT Frog offers the smallest packed size of all the products tested but it's more of a single-use bivy because it can be easily torn and rendered useless (think giant yard leaf bag).

Conclusion

Climbers and ultralight backpackers alike may be interested in a bivy for numerous reasons. In addition to an emergency shelter, these products can be a lower weight and a smaller alternative to a tent. A bivy can allow you to sleep in a multitude of places where a tent would not be possible. A lot of factors need to be considered when selecting a bivy, ranging from weather resistance to pack size.

When to Switch from a Tent to a Bivy?

The most common reasons to buy a bivy sack rather than a tent are to reduce pack weight and pack size by utilizing a sleeping system that is both lighter and smaller, yet still able to provide some shelter from the elements. But there is an active debate in the ultralight backpacking community about whether bivy is a better solution than an ultralight tent or tarp shelter. Bivies are still easier to set up than even the best UL tents and tarps, especially if you're looking for a solo shelter equipped to deal with the stormiest weather, and mainly winter snow conditions.

A few salient points:

A tent offers comfort with a lot of floor space which gives you room to sit up, read and hang out, or store gear. An ultralight tarp can also offer a similar amount of room that a tent does, with even lighter weight, and improved protection in the rain over bivies. In a sustained rainstorm, a tent or tarp is much more comfortable than bivies. Many people don't realize that some bivies can give you enough headspace to read or to sit up a bit so you can comfortably sip your coffee or slurp your miso soup.

Regardless of whether a bivy has those features, some of these traits are not needed by everyone, and they may be worth sacrificing in the name of less weight and space used up in your pack. By shedding extra material, poles, zippers, and doors — bulky components of a tent that are difficult to avoid — a camper can be reasonably comfortable while sitting out poor weather in the smaller enclosed space of a bivy. However, there is a limit to how many hours or days a person can comfortably wait inside a cramped bivy.

For this reason, we recommend that extended backcountry trips with the possibility of poor weather might be better spent in a tent or tarp. For quick trips where a storm can creep up in a moment's notice, or for adventure excursions that require the lightest packs so you can be fast on your feet, a bivy sack can perform and protect as well as a tent.

Indeed, at first glance, a bivy is just a micro-tent, lighter, and smaller with all the protection and less bulk. They are also much more mobile, able to be used on any flat surface long enough to stretch out on, and narrow enough to fit on tight rock ledges and small patches of soft grass. And some bivies don't need trees or anything to anchor them down or guy them out. They can also keep you warmer in cold weather than some tents do, and certainly warmer than a quick tarp setup.

The bottom line is that you can make a bivy work where a tent will not — high rock ledges, tight snow caves, tiny flat campsites on rocky terrain. Depending on your needs, a bivy can fluctuate from a fraction of a pound to up to two pounds, and even more so in price. While you can now find options for full-sized ultralight tents that are less than two pounds, these tents aren't usually four-season shelters, and they lack the versatility that a bivy sack of similar weight will give you. Another reason people will use a bivy is when they are headed on long adventures and want something to protect them from the elements in an emergency or if they find themselves unexpectedly benighted. Bivies give you the most versatile and lightweight option, and for those who prefer sleeping under the stars, a great alternative to tent camping!