Everything You Need To Know About Ultralight Bivy Sacks
- Bivy Sacks are perfect for the minimalist backpacker who's more concerned with logging miles
- Bivy sacks are used by the military, mountain climbers, touring cyclists and hikers.
- Most Bivy sacks on the market today are made with special weather resistant materials like Gore-Tex, which is a water-proof, breathable fabric.
As ultralight backpacking gains more mainstream attention, more campers are trading their tents for a new bivy sack.
Backpackers are sacrificing space when they sleep to save weight in their pack.
They’re reporting a more enjoyable experience on the trail with less fatigue and body aches.
In this article, we explain what bivy sacks are and why they’re such great ultralight shelters.
We also hope to clear up any questions you might have surrounding these amazing lightweight camping solutions!
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What is a bivy sack?
A bivy sack, also known as a bivy bag or a bivy shelter, is a portable, lightweight, waterproof shelter.
They’re perfect for the minimalist backpacker who’s more concerned with logging miles than sleeping in a portable hotel.
They can almost be thought of as a mix between a sleeping bag and a tent, and are a perfect tent replacement if you don’t need the extra space that you get with a tent.
Nowadays more and more backpackers are focused on staying lightweight on the trail as they see how a lighter pack helps you trek longer with less strain on your body.
Many backpackers are also noticing they don’t need the extra space you get with a heavier tent.
In most cases, the only thing you need a tent for is simply to rest your head at night.
If that’s the case then why not shed a pound or two by going with a bivy sack?
If you’re trying to figure out whether to go with a tent or a bivy sack, check out our article that compares the differences between bivy sacks vs tents.
Who uses bivy sacks?
A good ultralight bivy sack is incredibly reliable.
Along with backpackers, bivy sacks are used by the military, mountain climbers, touring cyclists and hikers.
These are all people who need a lightweight shelter solution that takes up very little space in your pack and can be used at a moment’s notice.
Bivys in the mainstream
Lately, the idea of ultralight backpacking has gone from a fringe group of daredevils to become an almost mainstream way of backpacking.
All over the internet hikers on forums are advising ways to cut weight out of your pack down to the gram.
There are backpackers who will go so far as to cut their toothbrush in half if it means less weight on their backs.
We are not advocating for you the reader to take your adventure to that kind of extreme.
On the other hand, these weight cutting hikers are reporting more enjoyable experiences on the trail. Probably because they don’t have to lug as much cargo around.
It makes sense because as you spend your days covering miles, walking up giant hills and crossing through rough terrain, the last thing you want is your pack weighing you down and increasing the work for your back and legs.
Great for long distance
Especially for those of you who are planning longer trips, the miles can really add up.
The first day or two you might feel the rush of the outdoors and that alone might power you through.
Eventually, the physical pain and fatigue starts creeping in and takes a toll on your body and your spirit.
The more pounds you can cut, the longer you can hike with less strain on your body.
Whether you’re on a shorter backpacking trip (1-3 nights), or even a long distance thru-hike like the Appalachian trail, a bivy sack can provide excellent overnight accommodations at a fraction of the weight you’d get with a tent in your pack.
No need to spend time and effort setting up a campsite only to break it down and do it all over again the next day.
Just pull the bivy out of your pack, lay it on the ground and slide in. Simple.
Bivouac shelter evolution
The name “Bivy sack” is actually derived from the term “Bivouac shelter” which entails any improvised shelter for temporary use.
They were first used by mountaineers and climbers who needed a more lightweight and more compressible solo shelter solution.
The early bivies acted more as a waterproof, emergency sleeping bag than an actual accommodation.
Bivy popularity grew once the military began to issue bivy covers to the troops.
These were perfect for soldiers who spent days at a time away from any reliable shelter.
They also had to be ready for unpredictable sleeping situations.
These soldiers were also trekking miles every day in physically demanding conditions.
Carrying bivy sacks helped lighten their packs and alleviated strain on their bodies.
Bivy sack features
Today’s commercial bivy sacks have evolved to include a number of features that make them the perfect outdoor shelter for you and your sleeping bag.
On the lower end, they can act as a protective shell that you simply slide over your sleeping bag.
Of course, you can spend a few more bucks and get a bivy with a hooped-rod that provides some distance between the inner lining of the sack and your head.
Some sacks are actually big enough that you could potentially fit your pack inside as well.
Most bivy sacks on the market today are made with special weather resistant materials like Gore-tex, which is a waterproof, breathable fabric.
This makes them great for snow and frigid temperatures as the sack provides insulation that traps your body heat and can help provide a nice toasty temperature without getting too hot and clammy inside.
They’re very effective in protecting you from rain, snow, gusty winds and most other extreme weather.
Why bivy sacks are great for backpacking
The biggest bivy benefit is its convenience, especially when it comes to setting up and breaking down.
Most bivy sacks can provide reliable shelter in even the tightest spaces.
As opposed to a tent where improvising can be more of a challenge and you need some location scouting.
Especially when you’re out in unfamiliar territory you can need shelter at a moment’s notice.
One minute you’re taking a selfie overlooking the mountain you just hiked, then you feel a few raindrops, and before you can even hit save on your phone you’re standing in the middle of a torrential downpour.
There is nothing worse than trying to set up your shelter in foul weather.
For the inexperienced camper, setting up a tent in perfect conditions can be a challenge..
Then add rain and wind, and the will of even the most experienced backpacker is put to the test.
You’re running around looking for dry ground while trying to keep the inside of the tent dry.
Meanwhile, you and everything you’re wearing is getting soaked.
Once the tent is finally up the inside is leaking onto your already wet body…
Needless to say, all the extra room you get in the tent isn’t going to help you dry off.
But, if you packed away a bivy sack, you can be safe and dry in less than a minute.
Bivy sack accessories
It’s highly recommended that you also use some kind of footprint underneath the sack.
When constantly used the bivy will experience a good amount of wear and tear.
Keep in mind that most bivy sacks use a durable grade of nylon coated with anti-fungal coating to create a disinfected, waterproof bottom, just like a good tent.
Over time, however, the quality will decline, so its good invest in a good footprint.
You can buy a quality one here:
Or you can just make one yourself out of a lightweight tarp or a sheet of Tyvek tarp (which is very lightweight), or ultralight polycryo plastic.
Bivy sack downsides
As great as bivy sacks are, there are some drawbacks that any prospective buyer should be aware of.
The most important thing you must keep in mind is that your sleeping space will become very tight.
Although there is room in most bivy sacks for some tossing and turning, sleeping on your side, or even reading and playing games on your phone, there will be no space to actually sit up.
This isn’t a big deal for a lot of people.
If you have any issues with claustrophobia a bivy sack might be a challenge.
Then again if you are claustrophobic, sleeping in a sleeping bag might also present some problems.
Gear storage space
Also, keep in mind that many bivies aren’t big enough to fit you and also fit your pack.
Most campers will just leave their pack outside the bag and that works just fine for them.
Worse comes to worse you can always pull your most valuable items, like your wallet, phone, or gun, out of your pack and keep them in the sack with you.
Some bivies even have separate pockets for just this kind of occasion.
While a bivy sack is a perfect shelter to pull out if you get caught in a surprise storm, waiting out a long weather delay in a bivy can be tough.
If you don’t have claustrophobia, waiting anxiously inside a bivy sack for a storm to pass can develop claustrophobia.
Bivy sacks get warm
For as effective as the bivy sack is at keeping you toasty in frigid conditions, a bivy can get hot fast.
Even with gore-tex included a lot of people tend to heat up fast inside a bivy sack.
To help with this a good number of bivies on the market come with a mesh bug screen built into the head so you can open the top and let air circulate.
Especially on a nice, clear night, this can give you a nice view of the stars to fall asleep to.
If these concerns don’t scare you off, and your inner navy seal is fired up about roughing it in the outdoors then the bivy sack is right for you.
The sacks themselves come in a number of different styles and cater to a wide range of needs.
You really can find the right one to fit your specific needs.
Today’s market offers such a wide variety of bivies that you’ll be hard-pressed to not be able to find your perfect sack.
Last update on 2021-04-22 / Affiliate links / Images from Amazon Product Advertising API
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