In this article, we explain why a waterproof bivy sack is a great ultralight backpacking shelter option.
Of course, you hope for clear skies and lots of sunshine, but as any seasoned trekker knows, those are some long odds. Especially if you’re heading out for more than a day or two, there’s a good chance you’re going to experience some rain.
Some of the most important gear decisions you are going to make involve how to best deal with unpredictable weather. This includes deciding between shelters.
A high-quality waterproof bivy sack is the most flexible, reliable item you can bring to protect you from the unpredictable weather.
What Is A Bivy Sack
A bivy sack is an ultralight outdoor shelter that ranges in usefulness as simply a sleeping bag cover to a tent substitute.
Original Military Bivy Sack
Bivy sacks were originally designed and used by the US military as a lightweight camping solution for soldiers in the field.
From there they became popular with early outdoor adventurers like mountaineers and long-distance cyclists.
These early bivouac shelters worked perfectly as they eliminated the need to carry a heavier tent.
However, they were not known for being comfortable and came with their own set of inconveniences.
Bivies have grown in popularity over the years and are now used as a primary shelter for ultralight backpackers and long distance thru-hikers.
Convenient Ultralight Shelter
They’re one of the lightest shelters you’re going to find weighing usually between 1-3 pounds at the absolute heaviest.
Most bivy sacks also come with a stuff sack which helps in giving you the ability to pack it down nice and tightly.
Overall they take up very little space in your pack and add very little weight for you to carry.
Sleeping Outside Without A Tent
Many traditional campers can’t imagine the idea of hitting the trail without a tent.
They’ve justified the extra weight and work of pitching a tent as just part of the camping experience.
But if you want your adventure to be more about hiking than about actual camping, you’ll find a bivy sack is a perfect solution.
Ultralight Tent Alternative
As great as tents are, if you’re a solo backpacker, you may not need the extra space that a tent offers.
Especially if you plan on trekking long distances for lots of hours, a bivy sack will make hiking easier on your body.
Even just saving the few extra pounds that you get from a bivy sack over a tent will make a tremendous difference.
Not to mention, many modern-day bivy sacks are now designed with a number of features which make them more of a tent substitute than just the sleeping bag cover they were originally built as.
Features that you’ll find on a bivy sack include:
- Waterproof fabric
- Bug Netting
- Overhead Hoops For Pitching
- Stuff Sacks
- Extra Insulation
These features give you extra protection from the harsh elements of nature that you get with a tent.
At the same time, a bivy sack naturally allows you some extra exposure to the beauty and ruggedness of nature that you miss in a tent.
Waterproof Bivy Sack
One of the most useful features of a bivy sack is its protection from the rain and snow.
This is also one of the oldest features and exactly what bivies were designed for in the first place.
Even the most basic bivy bags come with waterproofing and are guaranteed to keep your sleeping bag dry.
Emergency Bivy Sack
While more advanced bivies won’t necessarily keep you any drier, they will offer you extra space and air circulation.
Even if you don’t use it as a shelter, an emergency bivy is great for waiting out long storms.
Sometimes on the trail, you get caught in bad weather and have no shelter to wait out the storm.
Pitching your tent can take too much time and work.
A bivy sack, on the other hand, can simply be pulled out of your bag and rolled out in 2 minutes.
Plenty of backpackers carry waterproof bivy sacks just for these situations.
As you search for a bivy sack that provides excellent waterproofing, make sure you keep your eyes open for anything made with Gore-Tex.
The waterproof Gore-Tex membrane is a reliable, highly breathable fabric that is built into many bivies on the market today.
Gore-Tex consists of a multi-layer membrane that both keeps water out while allowing internal condensation to escape.
It makes your bivy sack more comfortable and for many people actually sleepable.
A lot of backpackers who use bivy sacks complain that they wake up in the morning wet due to the build-up of condensation inside the sack.
This was a huge problem for many of the early bivy sacks.
Especially since the whole point of the bivy was to keep you and your sleeping bag dry.
Gore-Tex pretty much eliminated this problem by allowing that condensation to escape through its membrane.
There are other lines of waterproof fabrics that you’ll find on bivy sacks, but they’re not as effective as the original Gore-Tex.
Waterproof Bivy Sack Features
While some people can rough it with just a bivy bag cover, others want something more that will offer space, comfort, and safety.
One of the first things that scare people away from bivy sacks is their lack of space.
In 2018, however, there are a number of bivy sacks that offer more room inside than you found in older bivies.
Many modern-day bivies are built long enough and wide enough to fit bigger campers.
You can even stake it to the ground to stretch it out and take full advantage of those dimensions.
Once fully pitched this bivy sack will give you enough space to fit you, your sleeping bag, and your most important belongings.
For maximum comfort, make sure you look for a bivy sack with a hoop over the face.
This is usually a single rod that easily slides through the bivy outer material to create a dome.
This helps keep the inner materials off your face for extra breathing room.
One of the most useful features of any bivy sack is bug netting built into the headspace.
The netting is usually made from mesh and its main purpose is to keep out bugs while you have the top of the bivy sack open.
Especially on warmer nights, this feature allows you to enjoy the outdoors to absolute maximum!
You get the added air ventilation, the cool breezes from outside, the view of the stars above, all without having to worry about any creepy crawlers or mosquito’s invading your space.
A lot of waterproof bivy sacks are used in the winter.
They are very popular amongst mountaineers and snow hikers.
To start, the exterior waterproofing keeps the snow moisture from seeping inside bivy sack.
You also get a much warmer internal temperature because of the tighter space.
Your own body heat is used to keep the bivy sack nice and toasty.
Many winter backpackers have complained that even in frigid temperatures they still get hot and sweaty inside their bivy
If you have a waterproof bivy with Gore-Tex, you’ll be able to eliminate much of the condensation and moisture build up inside.
They are also much easier to set up in bad conditions.
The stuff sack is the carrying case of the bivy sack.
The best part about a stuff sack is that it helps shrinks the bivy down to the size of a water bottle.
Once fully packed away, the stuff sack helps to keep the bivy from taking up a lot of space in your pack and helps keep you organized on the trail.
Ultralight Waterproof Bivy Sack
For the ultralight backpacker, a waterproof bivy offers a lot of value.
Ultralight backpacking is all about carrying the least amount of weight possible in your pack.
Since your shelter is the heaviest piece of equipment you’ll carry, the bivy sack eliminates a lot of weight from that equation.
Along with the tent itself, you have to also carry stakes, frame rods, and an extra rainfly.
All in all your shelter weight can easily top 6 pounds, and for the ultralight adventurer, this is not ideal.
A waterproof bivy sack is a 1 step solution that needs no extra parts like a rainfly.
Even most of the hoop rods that come with many bivies weigh only a few ounces but are worth it.
Downsides To A Waterproof Bivy Sack
As great as bivy sacks are they are definitely not for everyone.
Despite being lightweight, easy to use, and fully waterproof, a lot of backpackers find them hard to sleep in.
If you’re claustrophobic or a light sleeper the tight space can be challenging.
Even if you’re not claustrophobic there is some mental fortitude that goes into sleeping in a bivy sack.
Little Vertical Space
There is not a lot of vertical space so most bivy sacks are impossible to sit up in.
This isn’t a problem if you’re just laying down to fall asleep.
However, if you’re looking to kill some time inside your shelter reading, playing cards, or just looking at pictures you took on the trail, a bivy sack will not give you a lot of space to get comfortable.
Internal Condensation Build Up
Another big problem is that a lot of bivies build up internal condensation.
This can be alleviated by opening the top head part or buying a bivy sack with Gore-Tex, or some kind of air circulating membrane.
Although in warmer, humid conditions this can be hard to avoid even with the most advanced bivy sack.
No Room For Your Gear
Unless you are backpacking with an ultralight backpack in the “under 15L” capacity range, you will be hardpressed getting gear inside with you.
Plenty of backpackers have pulled it off.
However, plenty more just make peace with leaving their bag outside the bivy sack.
A waterproof bivy sack is a great solution for any backpacker who wants to travel light.
Gone are the days where you had to haul an 8-pound tent for just yourself.
Now you can have a reliable, waterproof shelter that takes up very little space in your pack.
A bivy sack works great for anyone who will be dealing with cooler temps and unpredictable weather.
Even if the weather is nice, a bivy sack will allow you to sleep comfortably under the stars with minimal setup and breakdown.
Anyone from a newbie backpacker to an experienced ultralight adventurer can benefit from camping in a waterproof bivy sack!