Bivy sack is short for "bivouac sack." Also commonly known as a Bivy Bag. It serves climbers who want lightweight emergency weather protection for sleeping bags during multiple-day ascents. The idea of zipping yourself inside a nylon bag may seem uncomfortable; ironically it’s the opposite. There are budget bivy sacks that are comfortable, lighter weight, smaller alternative to a tent which can be just as waterproof and durable. Bivy users actually sacrifice on comfort for the sake of reduced weight and small packing size.
What to Look For
Before considering buying a bivy sack, ask yourself, will it be too tight for you? While a tent offers a roomier, roof-over-your-head sensation, a bivy sack is almost like sleeping under the stars—a very liberating experience; you are protected from bugs and rain by a very lightweight barrier. Having said that, if tight makes you uneasy and too uncomfortable, then bivy isn’t for you. You definitely need a tent.
Bivies come with breathable/waterproof laminates such as Gore-Tex® fabric that enable for vapor produced by body heat to be pushed through (and out of) the fabric. This works best somewhere cool and dry; in rainy places, you should have enough overlapping material and zippers so it is unlikely you will have to completely zip them shut.
Condensation is a factor with bivy sacks. It’s a single walled tent and when vapor escapes from your body, it rises to meet colder air. At some point, the air won’t be able to carry it any longer, and therefore some may collect on the inner wall of the treated bivy fabric. Contrastingly, in 2-walled tents this moisture passes through the canopy and settles on the rainfly.
Bivies are stand-alone; however they need a few items to go along to make it comfortable for you.
o Sleeping Pad - the larger inflatable styles add comfort and insulation in mountain environments; non-inflatable closed cell foam pads do a good job in rocky and desert areas
o Pillow - Some companies make lightweight pillows and fleece-covered stuff sacks
o Sleeping Bag - Consider weather and temperature before selecting a product. These usually come filled either with soft and lightweight down insulation or durable and somewhat weather resistant synthetic insulation
Let’s look at these Bivy Sacks keeping budget as a top consideration.
Top 5 Budget Bivy Sacks
Tennier US Military MSS Mummy-Style Bivy Sack
This is an intermediate cold weather bag and has an anatomically designed foot box that contains twice the insulation as the bag for extra warmth. Air drafts are prevented by a sewn in quilted chest collar and the hood adjusts for heat retention.
Weight - 5 pounds
Dimensions - 36 x 1 x 90 inches
- Good insulation
- The draw string allows you to cover your face for extra warmth
- Compressible bag
- Heavy duty zippers
- Temperature ranges from 30° to -10° F
- Adjustable cinch-cord hood
- Water resistant
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This lightweight, durable, mummy style sleeping bag is ideal for cold to freezing weather. The Tennier Military MSS Sleeping Bags are a fantastic addition to anyone's outdoor kit! This patented state of the art Mummy Style Sleeping Bag has been tested and proven effective by the military for bivouacking in all types of inclement weather.
Slumberjack Contour Bivy
This serves great when you want to get deep into the high country for an overnight adventure and don't want to carry a tent. The mesh window has an awning to allow for ventilation and provides visibility. It has a Stuff sack included, is Fire Retardant & has waterproof taped seams. The arm ports make it easy to sit up and cook or look at your map while staying protected from the elements.
Weight - 1 lb 6 oz
- Dual zippers with hook-and-loop tabs allow for 'arms out' functionality
- Hooded design improves comfort and ventilation
- Four zipper sliders provide additional venting options and easy access
- Adjustable visor can be flipped open to expose a bug-free mesh window for increased ventilation
- Bivy may not always stand up straight and can fall on your face during the night
The lightweight Bivy combines waterproof breathable fabric, taped seems, unique “arms out” functionality and Kryptek Highlander camouflage. It has innovative shelter solutions that are lightweight, spacious, and durable. This compact Slumberjack Contour Bivy is the perfect sleep shelter for those looking to move fast and light, with sleep anywhere capabilities.
Aqua Quest Mummy - Waterproof Bivy Sack
It’s waterproof as most others from the Aqua Quest gear. The Mummy bag is designed to protect you from the elements and is a great addition to any camping setup or survival kit. It is Ultralight, thus packs down very small, so you can easily tuck it away for when you need it most.
Dimensions - 33.46 x 3.94 x 90.55 inches
Weight - 1.26 lbs
- Ultralight and compact
- Zippers on both sides to fit left and right zippered sleeping bags
- Easy setup
- Heat taped seams
- Laminated PU coating
- Condensation problems
This Aqua Quest Mummy Bivy Bag is extra wide for maximum comfort, so you can combine it with virtually any sleeping bag and by doing so enjoy an increase of approximately 9℉ (5℃) of additional protection from cold weather.
Sierra Designs Backcountry Bivy
Sleeping in Bivy doesn’t necessarily have to be uncomfortable where you cannot move around. The Sierra Designs Bivy makes it easy for you to sleep in a Bivy! Sierra Designs has created the Backcountry Bivy to fit their revolutionary Backcountry Bed and a 2.5" inflatable pad on the inside of the Bivy. You can go ahead and sleep how you want - whether on your back, side, or stomach - in this Bivy!
Dimensions - 82 x 32 x 4 inches
Weight- 14.4 ounces
- Waterproof and breathable
- Great ventilation - A mesh window gives you a view of the stars or closes up tight in bad weather and the large U shape flap can be left open
- Condensation around seams
When you're traveling fast through the backcountry, the Sierra Designs Backcountry Bivy gives you the ability to rest up anywhere you need to before hitting the trail another day. It’s a comfortable and roomy solo shelter. You don’t need to squeeze yourself and your sleeping setup into a cramped and tiny Bivy anymore!
Survive Outdoors Longer Escape Bivvy
This is considered as nothing less than a revolution in backcountry shelters. It’s Ultralight and has no condensation complaints. The fabric lets moisture escape and keeps rain, snow, and wind on the outside – all while reflecting your body heat back to you. Waterproof seams come with a drawstring hood closure and side zip to keep the elements away from you. The high-visibility orange exterior makes it easy for rescuers to spot you even in areas with high tree cover.
Dimensions - 84" x 31" inches
Weight - 8.5 ounces
- Highly breathable and waterproof
- Reflects 70% of radiated body heat
- High-visibility orange exterior
- Zipper is not fully waterproof
This can be considered as an emergency Bivy & usage for an ultra light sleep system, it’s very budget friendly, so if you’re looking for a Bivy hat doesn’t pinch the pocket and provides good protection , it’s Survive Outdoors Longer Escape Bivvy for you!
Today, bivy sacks are popular not only with the climbers looking for an emergency shelter in case they get stuck overnight, but also with ultralight backpackers as an alternative to a tent. If you’re someone who can ditch comfort to get into a bag to look and adore the stars, bivy sacks are aimed at becoming the best pick for your next trip!