Are Bivy Bags Waterproof?

If you have ever thought about ultralight hiking/camping then you have probably been recommended bivvy camping.

A bivy sack short for bivouac sack is similar to a single-walled tent that you can use as your primary sleeping system or even as an emergency shelter that is more compact and lightweight than a regular single-person tent.

The more important question, however, is how good their waterproofing is or if they are even water-resistant?

Depending on the materials used, a bivy sack can be completely waterproof, repelling every droplet and preventing any of your internal sleeping gear (most likely a sleeping bag) from getting wet. Alternatively, there are bivies that are partially water-resistant and are designed to protect your gear from minor splashes rather than the full force of the precipitation.

To help you better understand this, I did some research and put together a more detailed guide below.

Do Bivvy Bags Keep You Dry?

As I said before, a bivvy, particularly one made of waterproof fabric such as Gore-Tex or Sympatex, is highly breathable and will limit condensation build-up from your breath while also protecting you from the elements.

There is also another factor to consider: the structure of the bivy. There are two main types of bivy, zipper, and drawstring.

When dealing with heavy precipitation and relying solely on the bivy as a waterproof shelter, the zippered bivy is likely to be your best bet.

When zipped up, it blocks nearly all of the moisture from the surrounding environment, and even the seams prevent water from entering.

If interested, you can check this article on How To Repair A Bivy Sack?

While these bags can be quite expensive, most of them include a bug net (mesh layer) that makes them useful for warm weather camping or when the mosquitoes are at their peak.

The drawstring ones, on the other hand, are more prone to water seeping inside due to the way they work. When you use a drawstring one, you have to expose your head outside to prevent suffocation inside, which in turn allows water to enter.

That said, a drawstring bivy is much lighter than a zippered one as well as a lot more inexpensive. For an inexpensive yet light backpacking setup, you can simply use a tarp as the main waterproofing cover and a drawstring bivy to protect against any random water splashes.

How Does A Bivy Bag Work?

Think of a bivy sack as a large sleeping bag cover that acts as a raincoat for your main sleeping system.

A bivy bag’s primary function is to provide weather protection, similar to how a tent does, with a bit of extra insulation as a bonus.

The breathability, weather protection as well as insulation of this gear is highly dictated by the fabric used to manufacture them.

The higher the quality of the fabric, the more sophisticated and versatile the bag will be (which also means an increase in price).

The following are some of the most common materials used to make a bivy bag:

Do You Need A Tarp With A Bivy?

In short, while a tarp is not required for backcountry bivvy camping, having one provides more protection against the elements, especially if you are using a drawstring bivy.

Furthermore, they provide you with the necessary porch above your head, which can be extremely useful when it is raining outside and you need to change clothes or cook food.

Not to mention the privacy it provides by minimizing your footprint around the campsite, which in turn reduces unwanted attention from both other campers and wild animals.

How Do You Stop Condensation In A Bivvy Bag?

Here are some of the most common ways you can reduce condensation buildup inside your bivy:

Are Bivy Sacks Worth It?

So far, I have talked about the many benefits of bivy sacks and how they can be used. But do they really work?

The short answer is yes – but it depends on your situation. Unless you intend to spend a lot of time in them, there’s no real benefit to using them over a tent or hammock, which will provide more protection from the elements as well as be more comfortable.

However, if you plan to spend a lot of time in them, then you might as well go with a bivy sack. The reason is that, when you go ultralight hiking, you will likely have to travel a lot of distance on foot and you want your backpack to be as light as possible.

By reducing your weight, you could hike more comfortably and reach your destination sooner than you had originally planned.

In the case of short trips, where weight or compactness is not an issue, you are free to use any of the other camping setups.

Note that this does not imply that bivy camping is the most lightweight or comfortable option for hiking. Despite this, the easy setup and versatility of this camping method make it worth a shot.

Further reading: Are Bivy Sacks Worth It?

Final Thoughts

The primary purpose of a bivy bag is to offer weather protection while still being compact and lightweight to carry around.

Some bivy sacks are not partially waterproof (rather they are water-resistant with a waterproof coating) providing minor protection against random water splashes, and others provide complete weather protection regardless of whether you’re backpacking or mountaineering.

Anyways, as always, stay safe and happy adventuring!