Best Bivy Sacks To Survive Freezing Cold Temperatures

By Jason K. | Updated: 12/01/2023

Bivy Sack On Mountain In MorningToday I’ve got something extremely important to share…

A Complete Guide To Finding & Using a Bivy Sack For Freeze Cold Temps

Because when it comes time to survive the elements, you need a lightweight shelter you can trust.

But it’s hard to find a 4-season tent designed for one person that doesn’t weigh 3-4 lbs.

While that sounds light, 4 lbs. is a big addition to your pack in both weight and volume.

But there’s another option: A bivy sack!

TOPICS IN THIS GUIDE…    ↓(click to jump)
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Best Bivy Sacks For Sale Today

There are dozens of sleep systems and shelter options on the market today.

However, there are 2 main categories:

  1. High-End
  2. Emergency


The high-end offerings are largely from mountaineering companies.

These tactical sacks use high-tech fabrics and lighter weights, with prices to match.

These are designed for heavy-duty use in the worst conditions and repeat usage.

They are essential if gear failure could be the difference between life and death.

I’ve slept in 0-deg sleeping bags and mountaineering bivvies during rescue missions.

We’re talking in heavy wind and snow down to -15deg.

I won’t say it was my life’s “best” night of sleep.

But I stayed dry and reasonably warm.

It allowed me to catch some much-needed sleep before continuing the search and rescue mission:

RAB Storm Bivi One-Person Lightweight Shelter

RAB is a British company that makes great mountaineering gear.

They’re finally becoming more well-known in the US.

But you can still find their high-quality gear reasonably priced as they try to earn a following here.

The Storm Spartan provides what the name implies - a minimalist shelter from the elements.

There are no poles or fancy options, just a simple, breathable fabric cover with a mesh vent panel.

They claim a wider sleeping bag profile than other manufacturers. This should give you more space to move around in your sleep.

If you’re looking for a durable option with fewer elements to break down, this bivy sack is hard to beat!

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↓ FREEZING Solo Winter Wild Camp

Military Modular Sleep System 4 Piece Bivy Cover and Sack

Tennier has supplied integrated sleeping bags and emergency sacks to the US military for years.

These modular sleep systems combine a waterproof Gore-Tex outer bivy sack with two different weights of liner bags.

The specs claim it can provide insulation down to -40deg.

It’s not lightweight, but you know this gear has been tested.

I’m not sure I’d want to test sleeping in -40deg. But you know some poor recruit had to do it after carrying an 80lb pack and his rifle for 12 miles.

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↓ U.S. Army Modular Sleep System

Bonus Pick
Outdoor Research Helium Bivy

The Helium Bivy is renowned for its simplicity in setup and breakdown. 14% lighter than its predecessor, the Helium Bivy offers the essentials for outdoor minimalism without compromising.

Thru-hikers and bikepackers particularly favor this model for its compact design and weight efficiency.

Built with the robust, lightweight, and waterproof Pertex Diamond Fuse technology, it ensures durability and protection. The user-friendly clamshell opening enhances accessibility and durability, making it a reliable companion for expeditions.

Perfect for those who prioritize speed, agility, and performance, the Helium Bivy is the ultimate choice for the efficiency-focused adventurer.

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↓ Outdoor Research Helium Bivy

Emergency Bivvy’s

Finally, there are the “emergency sacks.”

These are mainly reinforced mylar tarps and space blankets.

A tiny, lightweight bivy focused on portability and retaining body heat rather than keeping the elements out.

An emergency bivy can be a super minimalist camping option if you expect cool temps, but the chances of snow or rain are low.

However, I wouldn’t advise using one if a blizzard is in the forecast.

3. Best Emergency Blanket / Tent
TACT Bivvy Emergency Sleeping Bag

This one is MY top pick.

IT's an incredible piece of survival gear.

Small enough to fit in your hand, this survival blanket utilizes Mylar.

Mylar provides the highest quality, most effective emergency blanket around.

And because it's taped together, it traps your body heat inside more like a sleeping bag than a blanket.

The Tact Bivvy is the best bang for your buck when you compare weight to warmth.

It provides maximum heat with minimal weight.

Making it perfect for bug-out bags, get-home bags, survival packs, or glove boxes.

Not only that, but it is windproof, waterproof, easy to use, and includes a small stuff sack.

This helps keep it stored neatly when you are not using it.

And the best part? It's affordable. At this price, it's an accessible survival tool for everyone.

Field Tested

We even tested the Tact Bivvy on a chilly 40-degree overcast day. "Just In Case," Jack (our managing editor) recorded temperatures inside the Tact Bivvy, and after only 10 minutes, it was a warm 82 degrees.

It was so warm inside the Tact Bivvy that he got out shortly after 10 minutes to keep from overheating.

If it works this well on a cool 40-degree day, it's a legitimate lifesaver in below-zero survival situations.

The bottom line is - The Tact Bivvy works and is excellent for cold-weather survival.

I recommend you get one for your bug-out bag, one for your medical first aid kit, one for your car, and your home.

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↓ Survival Frog TACT Bivvy Review

Survive Outdoors Longer 70% Reflective Escape Bivvy

This is a bivy sack with no extra bells or whistles.

It falls more into the emergency shelter than the adventure sack. So it's perfect for saving your life in a pinch.

Its water-resistant, durable fabric will keep you warm and dry because it will reflect 70% of radiated body heat and resists punctures and tears.

It also features:

  • a full-side zipper system
  • a draw-cord hood closure
  • and a foot box for comfort
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↓ SOL Escape Bivvy – Review

Primacare Emergency Foil Mylar Thermal Blanket (Pack of 10)

The last "bivy" option is little more than metallic foil meant to reflect your body heat.

I’ve found they’re difficult to manage in the wind. But wrapping them around me inside my sleeping bag adds some added insulation.

At an ounce or so each, they fold into a tiny flat package that slips into any corner pocket.

I keep one inside my first aid kit, where it’s been useful for treating shock for rescue operations.

As a side note: You can use these to reflect the direct sun and heat AWAY in hot sunny conditions. 

So they make an excellent sunshade tarp in the desert!

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Sol Bivy Sack In Desert

What’s A Bivouac Sack Anyway?

First of all, the term is short for bivouac.

The official definition of the bivouac is:

“a temporary camp without tents or cover used especially by soldiers or mountaineers.”

Otherwise known as – sleeping under the stars…

↓ Truth About Using A Bivy

And a sack is:

“a single-person tent distilled down to only the essential components.”

Putting the two together it’s a lightweight temporary portable waterproofing and breathability sleeping bag cover.

A cover lets you skip the heavy tent and stay protected from rain and snow.

Some models even include some nice features.

I’ve seen Bivouac sacks that include a bug net.

Others include a small pole system (to keep the fabric off your face while you sleep).

Helping from feeling too claustrophobic if you zip everything shut in bad weather.

All while keeping you warm and dry by blocking the wind and adding 10deg of insulation to your sleep system.

Soldiers, scouts, and mountaineers have used them for decades.

Because they’re lightweight, easy to set up, and low profile, this helps soldiers move fast, stay alive in harsh elements, and evade the enemy.

Modern materials (such as Gore-Tex) have made these sacks far more breathable and less clammy.

This results in a much more comfortable option for individual travelers.

Plus, it packs down small to take with you where traditional tent won’t.

The bottom line is:

Ultralight bivy bags are the ideal cold-weather protection for survivalists and ultralight backpackers.

And if you pair this sleep system with a sleeping pad – you’re not sacrificing.

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basic brown bivy sack

Best Bivy Sack Features To Look For

So, before we get into the different types, it’s worth a quick comparison of tents vs. bivy sacks.


This depends on the quality of the build.

There are both highly durable camping tents as well as emergency bags. So there’s no clear winner here. 

But look for one with ripstop nylon to ensure it can handle the snags you’ll find in the great outdoors.


A bivy sack is a hands-down winner here.

Even the heaviest ones come in at less than 2 pounds.

You won’t find many tents that light – and even fewer designed for extreme weather.

Pack Size

Again, the bivy has the edge.

While I’ve seen some pretty compact tents, mine is smaller than a water bottle.

It’s even smaller than my down jacket!


This one is a draw based on designs for similar conditions.

A four-season Gore-Tex sack may cost several hundred dollars.

But so will a tent designed with the same specs.

Conversely, some are very inexpensive, even under $50.

These aren’t the shelters you want for heavy repeat use in seriously extreme weather.

However, they provide a great option when you might not take shelter otherwise.

These more affordable options are best for emergencies or more temperate climates.


We can’t sugar-coat this one.

A tent is a more comfortable option in nearly every case.

At best, an emergency bag lets you lean on an elbow and read a book.

You won’t have the space to sort through your gear or spread out in one.

So it may be too small if a mummy-style sleeping bag makes you claustrophobic.

On the other hand, in cold weather, a tent has a lot of cold, dead air space to warm up.

While a bivy sack keeps your body heat close.

Dispelling A Few Myths

Myth 1. Only For High-Altitude Mountaineering

First and foremost, some folks think they’re only for extreme, high-altitude mountaineering expeditions.

But that isn’t the case, friends!

They’re a great option for anyone who wants to travel light and fast in the backcountry, whether you’re going for a weekend hike or a multi-day trek.

Myth 2. They’re Uncomfortable

Another myth is that they’re claustrophobic and uncomfortable.

I won’t lie to you; some can be a bit snug.

But that doesn’t mean they’re uncomfortable!

In fact, many folks find they provide a cozy, secure sleeping space that can enhance their overall camping experience.

Myth 3. They’re Terrible In The Rain

Some people also think they’re only good for dry weather.

But that’s not true!

While it’s true that some bivy sacks aren’t 100% waterproof, many are made with materials that can withstand rain and other wet conditions.

And if you’re worried about getting wet, you can always pack an additional tarp or rainfly to throw over it.

Myth 4. They’re Difficult To Set Up

Finally, some folks believe they’re difficult to set up and use.

But they’re actually one of the easiest camping shelters to use!

Find a flat spot to lie down, unroll it, and crawl inside. That’s it!

No poles to set up and no complicated rainfly attachments to fuss with. It’s simplicity at its finest.

So there you have it – some of the biggest myths debunked.

Who Should Own At Least One

Well, that depends on your outdoor activities and preparedness needs.

But you should pack an emergency bag if you spend time outdoors, hiking, hunting, fishing, etc.

They’re a versatile and valuable tool for various outdoor enthusiasts.


If you enjoy backpacking or camping in te wild, a bivy sack can be a lightweight and compact alternative to a backpacking tent.

It offers shelter and protection from the elements while occupying minimal space in your pack.

Plus, it’s easy to set up and take down, making it a convenient option for on-the-go adventurers.


If you’re a hunter, they can provide a safe and secure shelter during extended hunts.

It can protect you from the elements while you wait for your prey, and its small size means it won’t take up much space in your hunting gear.


For those who prioritize preparedness, it’s an excellent addition to your emergency kit.

It can be used as a temporary shelter during a disaster, protecting you from the elements while waiting for rescue or help.


Finally, for survivalists, these emergency shelters are a must-have item.

t can be used in various survival situations, from providing emergency shelter to trapping heat to staying dry in wet conditions.

Its compact size makes it easy to carry in a bug-out bag.

In summary, whether you’re a camper, hunter, prepper, or survivalist, owning a bivy sack can be a valuable investment for outdoor activities and preparedness.

Brief History Of The Bivy Sack

The history of bivy sacks, or bivouac sacks, is a fascinating journey through the evolution of outdoor survival gear.

Military Origins

Bivy sacks trace their roots back to military use, where soldiers needed portable and efficient sleeping solutions during wartime.

The concept was simple:

Create a shelter that was easy to carry, quick to set up, and offered protection from weather and the environment.

These early versions were rudimentary, often just basic waterproof covers, providing minimal insulation and comfort but critical protection.

Mountaineering Adoption

The true development of bivy sacks began with their adoption by mountaineers.

In the early to mid-20th century, climbers tackling high alpine routes needed lightweight, compact shelter options that could be used on ledges or in other situations where traditional tents were impractical.

The alpine bivy sack answered this need, offering a way to spend nights on the mountain without the bulk and weight of a full tent.

Material Advancements

A significant leap in bivy sack design came with advancements in materials.

Initially made from canvas or other heavy, minimally water-resistant fabrics, the introduction of nylon in the 1960s was a game-changer.

This lighter, more durable, and water-resistant material made bivy sacks more practical and comfortable.

Later, the development of Gore-Tex and similar breathable, waterproof fabrics further revolutionized bivy sacks.

Making them not just a survival gear but a viable alternative to tents for solo adventurers seeking to reduce their pack weight.

Popularity Among Solo Adventurers

In the latter part of the 20th century, bivy sacks gained popularity among solo hikers, backpackers, and mountaineers.

The appeal was clear:

Bivy sacks offered a way to experience the wilderness in a more direct, unencumbered way.

They facilitated a deeper connection with nature, offering the ability to sleep under the stars while being protected from the elements.

Modern Bivy Sacks

Today’s bivy sacks are marvels of design and technology.

They come in various styles, from minimalist covers to more advanced, hooped designs that offer extra space.

Modern bivies balance the need for weather protection, breathability, and low weight.

They incorporate advanced fabrics, waterproof zippers, bug nets, and even small poles to create a more spacious head area.

Final Thoughts

For a solo traveler, efficiency is critical, and a bivy sack is a great way to cut down on the bulk and weight of a tent in your pack.

They provide a fast and light shelter in a wide range of conditions.

Plus, they’ve been proven as a core piece of survival gear for our military.

With the wide range of options on the market, there’s one for nearly any budget.

If you haven’t checked them out yet, do it now!

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