The Best Bivy Sack Review
What is the best bivy sack? Throughout a stormy summer, four of the best models were tested in a variety of environments, from deserts to swamps to mountains. A handful of hard-core campers, climbers, and backpackers ranked the products based on weather protection, comfort, ventilation, and weight and awards were chosen for best value and the best option for emergency shelter. If you are someone who is looking to ditch a heavier tent and feel the freedom of sleeping under the stars, our comparative review of bivy sacks is aimed at finding the best pick for your next trip.
Read the full review below >
Test Results and Ratings
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Analysis and Award Winners
Best Overall Bivy Sack & Best Bang for the Buck
MSR AC Bivy
Top Pick for Weather Resistance
Outdoor Research Alpine Bivy
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Analysis and Test Results
Whether or not to bring a bivy depends on many factors, and everything from weight to weather to available space in an overnight pack can influence the decision. In our article How to Choose the Best Bivy Sack we dive into the specifics between available styles and help to distinguish key features and best uses for each model.
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 have unique characteristics that create compelling reasons to consider one for your next outing.
When to Switch from a Tent to a Bivy?
The most common reasons to 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 a UL tarp shelter. Bivies are still easier to set-up than even the best UL tents and tarps, especially if you are looking for a solo shelters equipped to deal with the stormiest weather, and particularly winter snow conditions.
We explore this question in more detail in our buying advice article, and recommend that article for those interesting in considering ultralight tents or tarp shelters as either alternatives to bivies, or to augment them (many people use UL tarps and bivies together to create a uniquely lightweight solution with excellent weather protection). But, we'll try to summarize the most salient points here below.
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 similar room as a tent does, with even lighter weight, and improve protection in the rain over bivies. In a sustained rain storm, a tent or tarp is much more comfortable than bivies.
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 set-up.
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, one can run anywhere from $80 to $240 and fluctuate from less than a pound to up to 2 pounds. While you can now find options for full-sized ultralight tents that are less than 2 pounds, these tents aren't usually 4-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!
Types of Bivies
In our review, we examined five different bivy sacks to find the one that performed the best overall. We focused primarily on weatherproof models with reliable construction. Bivies typically come in a few styles:
These are lighter and easier to pack than the more weather resistant models. They are designed for areas where wet weather is less of a concern than insects. These lightweight bivies can be used in tandem with a tarp if precip is a worry as well as bugs. In our test group, the Outdoor Research Bug Bivy was the only bivy in this category.
Lightweight, simple, and constructed without a set of poles or extra features that increase weight and bulk, minimalist models are ideal for most applications where weather might be expected and you plan to hike far and fast. These types of bivies don't usually provide absolute protection from the weather, but are a great option to throw in the bottom of your pack "just in case" you end up needing to spend the night. We tested two minimalist designs here — the REI Minimalist and the MSR AC Bivy.
These models typically have some form of wire or pole to keep the fabric off of the camper's face, and should be made of strong material meant to withstand repeated abuse in harsh conditions. These are what you would need if you think you'll be dealing with snow or winter camping or situations where protection from the elements is essential and prolonged. The Black Diamond Big Wall Hooped Bivy and the Outdoor Research Alpine Bivy are the models we tested that fit into this catergory.
Check out our Buying Advice article for an in-depth look at the different styles reviewed and our input on which might work best for your next trip.
Criteria for Evaluation
A great shelter protects from whatever weather might arrive without negatively affecting the camping experience. Several factors come into play when considering which type of weather to prepare for. Is rain or snow likely? Will the nights be cold? The main element that effects weather resistance is the type of fabric used for the bivy. Is it a mesh that won't protect from any precip? Is it the ultimate in waterproofness that will keep you warm and dry in cold weather, but not breath well and leave you sweaty in warmer conditions?
Different types of fabrics work best in different situations. A completely waterproof material, like Gore-Tex, will keep all the rain out, but even the most breathable versions have a harder time allowing water vapor from sweat or breath to escape. A ripstop nylon is lightweight and if treated with a durable water repellent (DWR) coating is typically more breathable, but since it isn't completely waterproof, is only ideal for lighter rain. A full-length bug net like the OR Bug Bivy can provide maximum ventilation and awesome views while keeping you safe from annoying critters, but will do nothing to keep you dry if it rains.
Some bivies are made for 4-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, and so are best reserved for emergencies or milder rain and temps.
The most weather resistant models we tested are the four-season OR Alpine and the Black Diamond Big Wall Hooped Bivy, both of which are made entirely with waterproof materials and can be completely closed up in the nastiest winds and storms. The MSR AC model and the REI Minimalist also are constructed with waterproof materials but have openings that can't be closed completely, which reduces their water resistance score and makes them best suited to lighter rain situations. The OR Bug Bivy, though it has a waterproof bottom, is the only model which provides only protection from insects, and should only be used in fair weather.
Like all camping shelters, the way it is used can affect weather resistance. When possible, picking higher ground or a clearing under a tree, will add a bit of extra weather resistance from the natural environment, avoiding 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).
A good bivy should be a lighter camping option than a tent with the equivalent protection. A few of the lighter weight models have extra bug netting in key locations instead of shell fabric in order to shave some ounces (such as the REI Minimalist)– something a camper in a very wet and cold environment may not appreciate. Also, an additional tent pole like the ones included with the four-season models (OR Alpine and BD Big Wall) might add a few ounces that just aren't needed if the top is to remain mostly open in dry conditions. Care should be taken to make sure your choice isn't too lightweight that it sacrifices the protection and comfort you desire. T
The REI Minimalist is the lightest weight model we tested, weighing less than a pound. The MSR AC deserves an honorable mention here, given that at 16 oz it is only one ounce heavier than the REI Minimalist, yet offered better performance in every other metric. The heaviest is the OR Alpine, weighing 2 pounds, which is still far lighter than a standard backpacking tent.
Many bivy sack users feel that small packed size is one of the key features they seek. Extra bulk in a pack often can't be afforded and, more than just the weight, the packaged size of the product can determine whether it is appropriate for the next trip or simply a large inconvenience that will get left at the car. The models that include separate tent poles can have the long obstructive sticks stored elsewhere (perhaps on the outside of a pack or along the inside wall) so that the bivy inside the stuff sack can be crammed into any available spot in a pack. By dropping down from a tent to a smaller bivy, you might be able to save up to 5 liters of space, allowing for a smaller pack overall or room for other essential gear.
We measured each product when packed up in its (usually provided) stuff sack. Some of the models had poles that could be added to the same stuff sack or stored in your pack separately. The MSR AC offered the smallest packed size of all the products tested, with the REI Minimalist coming in a close second place. The BD Big Wall was the largest.
Ventilation in bivies can be a tricky thing. Just like any piece of waterproof gear, 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 value and performance.
There are a lot of human factors that can make your night miserable even in a great bivy. But of course, we at OutdoorGearlab are here to give you the info you need to make your experience in the wilds a great one. There 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 of time where complete protection is necessary, we recommend 'cracking' the mesh or zipper to allow some movement of condensed air inside. However, if dry weather is not in the forecast, the two critical things to keep in mind are to make sure you are breathing outside the bivy and to not use a sleeping bag or pajamas (or whatever clothing you sleep in, if any) that are any warmer than what you need 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 like the Mountain Hardwear Hyperlamina Flame instead of a down sleeping bag since synthetic insulation can still retain insulating properties and keep you warm if it gets damp or even soaked.
If your bivy is able to 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 greatly increases its ability to ventilate. The OR Bug Bivy was the most breathable of our test group, which should be hugely obvious due to its mesh material. The OR Alpine Bivy, though a fully waterproof four-season model, has several features that aid in proper ventilation, such as a pole around the face and guy points to stake it out for more air space inside.
Comfort is always an important criteria 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 general size considerations), ease of use, and added features, such as gear pockets or straps that 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 shelter for less weight and space taken up in your pack, you should also expect less space for you inside, but not to the point of discomfort. We compared not only floor space, but head space and width at the shoulder– all of which influence the comfort rating. 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 MSR AC Bivy is the widest and the BD Big Wall Bivy is the longest of the products we tested. While the OR Alpine Bivy is both the shortest and narrowest of the bivies, it has a pole at the head which keeps the material out of your face, making it feel much less claustrophobic than other bivies in the group that might be wider or longer. Both the REI Minimalist and the MSR AC lost some points because they have openings that are difficult to keep off the face and that do not close completely. We give the OR Bug Bivy special mention here, because if you are sleeping in a mosquito infested zone, nothing is more relieving or comfortable than being surrounded by bug mesh.
When planning what sleeping system works best for you, its important to take all components into account. Your shelter, sleeping bag, and sleeping pad all work together to keep you warm and comfortable. We recommend pairing a bivy sack with one of the sleeping bag from our Ultralight Sleeping Bag Review. Our favorites were the Katabatic Gear Palisade and ZPacks 20 Degree for their comfort and light weight. As far as sleeping pads, some of our favorites include the Therm-a-Rest NeoAir XTherm and the Therm-a-Rest NeoAir XLite. Through our testing we have found these two to be amazingly comfortable and warm even with their low weight. For a more detailed look at all the sleeping pads we reviewed, check out The Best Sleeping Pad Review.
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 lighter weight and 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. For more information on whether a bivy is the right choice for you and what to consider when making your purchase, check out our Buying Advice article.
— Sarah Hegg and Greg Davis
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