6 Best Bivy Sacks To Keep You Safe In Freezing Temps

By Just In Case Jack | Last Updated: September 27, 2018

Bivy Sack On Mountain In MorningWhen it comes time to survive the elements in an emergency, you need a light shelter you can trust.

Sure, there are tons of great camping tents on the market.

And there are even some lightweight survival tents.

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

While that sounds light compared to other shelter options, 4 lbs. is a big addition to your pack or vehicle. Both in weight and volume.

But there’s another option – a bivy sack!

So today, let’s cover the following bivy sack topics:

**Note: If you want our top recommendations, feel free to SKIP AHEAD HERE.

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Sol Bivy Sack In Desert

What’s A Bivouac Sack Anyway?

First of all, the term bivy 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…

And a sack is:

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

Putting the two together and a bivy sack is basically a lightweight temporary portable waterproof sleeping bag cover.

A cover is designed to allow you to 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.

Heck, soldiers, scouts, and mountaineers have used military bivy sacks 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, their small footprint allows you to use one in places that wouldn’t allow for a traditional tent.

The bottom line is this:

Ultralight bivy sacks are the ideal piece of gear for cold weather protection for survivalists and ultralight backpackers.

And if you pair this sleep system with a quality sleeping pad – you’re not sacrificing much comfort at all.

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basic brown bivy sack

Best Bivy Sack Features – Tents Vs. Bivy Sacks (Pros/Cons)

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


Clearly, 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, a bivy sack 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 bivy sack may cost several hundred dollars.

But so will a tent designed with the same specs.

On the other end, 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 for those times 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, a bivy sack allows you to lean on an elbow and read a book.

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

If a mummy-style sleeping bag makes you claustrophobic, a bivy sack might be too small for you.

On the other hand, in cold weather, a tent is a lot of cold, dead air space to warm up while a bivy sack keeps your body heat close.

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TACT Bivvy Main Image

6 Best Bivy Sacks On The Market Today

There are dozens of models of sleep systems and shelters on the market today. However, there are 2 main categories of bivy sacks:

  1. High-End
  2. Emergency


The high-end offerings are largely from mountaineering companies.

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

These are designed for heavy 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 my 0deg sleeping bag and a mountaineering bivy during mountain rescue missions. We’re talking in heavy wind and snow down to -15deg.

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

But I stayed dry and reasonably warm.

It allowed me to catch a couple of hours of much-needed sleep before continuing the search and rescue mission.

1. Outdoor Research Alpine Bivy

This OR bivy sack is made out of waterproof Gore-Tex fabric. It includes fully taped seams and water-resistant zippers.

The single hoop pole keeps the material up away from your face while you sleep.

The No-See-Um mesh keeps biting insects out if you want to keep the main zipper open for a breeze.

It weighs in at under 1.5 lbs and packs down smaller than a water bottle!

2. RAB Storm Spartan Bivy

RAB is a British company that makes some great mountaineering gear.

They’re finally becoming more well-known in the US. But you can still find their high-quality gear at a reasonable price as they try to earn a following here.

The Storm Spartan bivy provides what the name implies – a VERY 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 a little 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!

3. Tennier Military Modular Sleep System

Tennier has been supplying integrated sleeping bags and bivy sacks to the US military for years.

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

In combination, 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.


Finally, there are the “emergency bivy” sacks.

These are mainly reinforced mylar tarps and space blankets.

These tiny, lightweight emergency shelters are more about retaining body heat than keeping the elements out.

Emergency bivy sacks can be a super minimalist camping option if you’re expecting 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.

4. S.O.L. Survive Outdoors Longer Escape Bivvy

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

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

It will keep you warm and dry with its water-resistant, durable fabric 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

5. Survival Frog Tact Bivvy

TACT Bivvy In HandWe’ve featured gear from Survival Frog in the past, and for a good reason.

This ultralight bivy sack is just the essentials – in a 4.8-ounce package. It packs into a tiny stuff sack that won’t fill your pack.

The reflective lining directs body heat back into your sleeping bag.

The material is waterproof, windproof, and tear-resistant. This makes it a smart addition to your survival arsenal.

“Just In  Case” Jack (Skilled Survival’s editor-in-chief) field-tested the TACT Bivvy and was impressed. Here’s what he had to say:

I recorded temperatures inside the Tact Bivvy on a cool 40-degree day. After only 10 minutes inside it was a warm 82 degrees!

Outside Temp / Inside Temp

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.

At the time we published this post, Survival Frog was offering a 20% discount plus a box of waterproof matches!

Click here to see if this fantastic deal is still available!”

So wherever you’re spending the night – in a tent or cabin – use it as an outer shell around your standard sleeping bag.

However, it doesn’t have a zipper closure, and the Mylar material is not breathable.

But it makes sense to stash several.

So add one to your vehicle’s glove box, daypack, bug-out bag, tactical backpack, and get-home bagjust in case.

6. Mylar Emergency Blanket

The last “bivy” option on the list 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 up 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 a great sunshade tarp in the desert!

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 quick, lightweight shelter in a wide range of conditions.

Plus, they’ve been proven over the years 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!

Jason K.

P.s. Are you ready for the tough times ahead?

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