bivy sack

The Bivy Sack Buying Guide: Best Bivy Sacks

Named for the “bivouac” sack, bivy sacks are lightweight and easy-to-carry waterproof shelters that function as a more convenient alternative to traditional camping tents. They’re generally employed by minimalist hikers, climbers, competitive racers, backpackers, and campers, and are regularly used by foot soldiers.

Bivy sacks are designed as solo shelters for outdoors enthusiasts who prefer to travel in ultralight mode via lightweight and easily compressed gear. The original bivy sacks were little more than simple single-person sleeping bag covers that provided basic protection from the elements.

bivy sack

Bivy sacks are a no-nonsense staple for active outdoor recreationalists. Constructed with sleep and rudimentary protection in mind, they provide an excellent alternative to bulky tents that take up space and assembly time. Furthermore (and fortunately), with today’s modern technology bivy sacks are more conducive to one’s individual needs than ever.

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Buying Basics

As with all recreational and camping gear, it’s important to target your specific needs to find the most suitable product. You may be unfamiliar with the variety of bivy sack options on the market today, but there are a number of helpful guides to take you through the various designs and personalized components.

Frequently used by cross-country backpackers, along with hikers, climbers, and competitive racers, the bivy sack is ideal for the independently active who wish to travel as light as possible. Because of the bivy sack’s bare-necessities design, it’s best suited to those seeking little more than a snug place to sleep with a bit of protection from the damp and chill.

Today’s bivy sack consists of 2 layers, or tiers, of fabric: the bottom tier generally consisting of a sturdy urethane-coated nylon (usually taffeta or oxford), with the top tier made with a lighter waterproof nylon. In more advanced bivy sacks, multiple layers of laminate are applied for added durability and fortification.

water repellent shellalinja

Most bivy sacks include an opening for your head, with rainfall welcoming potential moisture inside. T.D. Wood writes for Wild Earth: “A camper can minimize that risk by pulling the headhole’s drawstring very snuggly. Doing so, of course, turns the head hole into more of a nose hole, which some people find far too restrictive. Yet this is a small sacrifice to ultralight travelers who prize a bivy’s next-to-nothing weight.”

Some bivy sack models have armholes on the sides to allow for cooking, gear sorting, and other tasks to be performed without having to leave the bivy encasement. Additionally, full-length zipper openings offer maximum ventilation, while some models even include special straps for securing your sleeping pad and preventing it from slipping or sliding around.

Some bivy sack users prefer to skip a sleeping bag altogether in warmer weather and simply sleep inside the shell.

Bivy sacks have naturally evolved into extensions of their primitive prototype, resulting in solo-style tents known as bivy shelters. The bivy shelter is a slightly more amped up version of the sack, with more traditional tent-like components, namely an expanded head space area and full enclosure to shield one from insects and unfavorable weather conditions.

Some bivy shelters feature small suspension systems such as poles, hoops, and/or stiffened wires to add a bit more “sit up space.” These additions generally add between 2-4 extra pounds of weight to a camper’s gear.

Whether or not you opt for a more basic bivy sack or sophisticated tent-like design depends largely on the conditions you’ll be traveling in, as well as personal standards of comfort. Those who prefer more space and sense of security will likely prefer a more upgraded bivy sack with pole-and-line technology, as well as reinforced lining.

However, those desiring the least amount of added bulk and weight to their gear will opt for the simplest, true-to-origin bivy sack.

To recap, the bivy sack is intended to provide 2 basic functions: to keep one’s sleeping bag dry, and provide a little extra heating insulation, generally providing a 10 degree difference in temperature inside vs out. From there, however, one can select from a number of bivy sack designs.

Things to Consider When Buying A Bivy Sack

Many who consider investing in a bivy sack are hesitant due to the design’s pointedly restrictive space allowance. While a traditional camping tent provides a more comfortable makeshift roof over your head, a bivy sack places very little between you and nature–a bonus for true lovers of the outdoors, and unsettling positioning of vulnerability for others.

While bivy sacks offer solid protection against the elements, they are not for the fussy or faint of heart. Riding out a storm or particularly cold night in a bivy sack can make or break a user’s resilience.

Air circulation is another factor to account for when buying a bivy sack. Laminates such as Gore-Tex are both breathable and waterproof, with vapors produced by body heat cycled through the fabric strands and pushed out, all the while repelling rain water and dampness.

goretexWart Dark and Solipsist

Most agree that bivy sacks are best suited for cool, dry environments in which the body’s natural humidity isn’t exacerbated by extreme weather conditions.

Condensation can be a potential issue with bivy sacks, as they are essentially single-walled tents. When heated body vapors escape they rise to meet colder air; when the vapors come in contact with the bivy fabric the air can no longer carry all the moisture, which then collects inside the laminated fabric. While standard 2-walled tents allow moisture to pass through the tent’s breathable canopy and settle on the rainfly, this can produce a slight amount of dampness on the singular inner wall of a bivy. In icier conditions, this could additionally lead to a thin layer of frost forming on the inside of the bivy sack.

The main concern for most bivy sack users is staying dry, and it’s to this end that the bivy sack definitely holds up. Though Gore-Tex fabric can sometimes put off a clammy sensation when wet, it undeniably keeps out water.

The key to a good bivy sack is state-of-the-art ventilation, which minimizes feelings of being soaked through or inconvenienced by damp conditions.

A recent article for Ranger Made states: “A good bivy will have no problem keeping moisture away. However, water puddles or snow may accumulate on top of the bivy especially around the feet area and actually press down to lean against your body. If your sleeping bag is thin, you will get cold. That’s why it’s a good idea to hang a tarp sheet over the bivy that would cover both you and your other gear. It will keep heavy rain and hail from hammering you, and will let you get out of the bivy easier in bad weather.”


Best In Bivy Sacks

So what are the best bivy sacks on the market today? How do you find one geared towards winter camping or conversely, light summer backpacking? Below are the top rated bivy sacks to suit all specifications.

Best Bivy Sack for the Money

An Amazon bestseller, the streamlined and budget-friendly Aqua Quest Mummy sack is waterproof, features 70D RipStop fabric, laminated PU coating, and heat taped seams for superior waterproof and breathability performance. Ultralight and compact, the ‘Mummy’ weighs in at just 1.26 lbs and packs down to 15″ x 5″ x 3″, making it ideal for basic cyclist and backpacker needs.

PROS:

  • Extra wide and long enough to comfortably fit anybody up to 6’6″, this bivy sack is ideal for taller travelers who need a bit more room.
  • Zippers on both sides to fit left and right zippered sleeping bags; can be used alone or inside any other shelter including tents, boats, or cold-weather shelters.
  • Fast and easy setup.
  • Extremely lightweight at just over a pound and a half.

CONS:

  • Most reviews report that the bivy sack is not very breathable, with one reviewer noting that “if you create condensation inside it, it stays inside it.”
  • No bug mesh on earlier models, so make sure you purchase the latest version.

Best Ultralight Bivy Sack

Measuring just 19.5″ high and 26″ wide and just 18oz, the Outdoor Research Helium Bivy is a super lightweight bivy sack that boasts all the standard waterproof and breathability features, with additional anti-fungal floor coating and five stake loops for sizing. Great for multi-day backpacking excursions in all climate conditions, this bivy sack packs extremely small and adds next to no weight to your gear.

PROS:

  • Extremely lightweight, packs down small.
  • Comfortable size, even for those inclined to claustrophobia.

CONS:

  • While no direct leakage or dripping was reported, some reviewers noted some seepage through the sack fabric during rainstorms, comparable to a tent without a rainfly.

Best Bivy Sack for Winter Camping:

Boasting 3 layers of fully breathable and waterproof Gore-Tex fabric, along with hydroseal and anti-fungal coated nylon flooring and fully taped seams, the Outdoor Research Alpine Bivy is a durable bivy sack that was made to stand up to the harshest of weather conditions.

One of Outdoor Gear Lab’s top-rated winter camping bivy sacks, the Alpine Bivy also features netting covers with zippered storm flap, as well as sleeping pad straps, five stake loops, and guy line looping. A roomy foot section and convenient internal mesh pocket for goods and valuables.

PROS:

  • Provides superior space for thicker sleeping pads and bags, and can be used in place of a single-person tent
  • GORE-TEX Respiration Positive fabric allows moist air to escape but blocks outside weather increments, minimizing condensation and chill.
  • Zippered base vent improves overall air circulation.
  • Lightweight and compact

Best Bivy Sack for Backpacking

Measuring 13 x 6 x 4 inches and weighing a little over 15 oz, the Sierra Designs Backcountry Bivy is a lightweight bivy sack is ideal for backpackers seeking basic protection on short-term excursions.

PROS:

  • 100% Waterproof protection.
  • Spacious interior.
  • Extremely lightweight and easy to pack/carry.

CONS:

  • As with most bivy sacks, sweat and condensation are a constant factor. Most reviewers suggest keeping the rain flap open on dry, clear nights for improved ventilation and air flow, as well as implementing an additional tarp if necessary.
  • No poles or frames to keep the fabric off your face.

Conclusion

Originally invented to serve the needs of mountaineers, soldiers, and climbers, the bivy sack is ideal for those accustomed to somewhat Spartan conditions, and are happy to sacrifice roomier and more comfortable camping options for ease of travel and mobility.

Long distance backpackers and touring cyclists looking for the most lightweight protection against the elements will find a number of suitable bivy bag options to choose from, with many updated models offering additional compatibility options.

It goes without saying that bivy sacks are not for the claustrophobic or those who prefer a cushier camping set up; the sacks are designed with regard for utmost utilitarian functioning. However, today’s more advanced bivy sacks take into consideration such comfort and space requirements, and offer a variety of models more akin to traditional camping tents.

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