The term ‘bivouac’ is derived from the French word bivouac, which means an encampment for the night. In addition to sleeping in a tent or a hut, bivouacking is another common way to spend the night in the great outdoors. In contrast to the other option, however, there is usually no roof over your head, unless you sleep in one of the rather sparingly equipped accommodations, known as bivouac huts. If you don’t have this luxury and still need a weatherproof place to sleep, there is probably no way around getting yourself a bivvy bag. In the following, we’re going to tell you all about bivvy bags, including what to look out for when buying one.
- Bivouacking in a bivvy bag.
- What is a bivvy bag?
- The basic characteristics of a bivvy bag.
- How to bivvy bags differ from one another?
- What is a bivvy bag made out of?
- Are there bivvy bags with membranes?
- Bivvy bag shapes and designs.
What is a bivvy bag and what does bivouacking mean?
Simply put: bivouacking is basically like camping, but instead of sleeping in a tent, you’re sleeping in a bag. Oftentimes, you won’t even sleep in it, but merely use it as shelter until a storm passes or wait for rescue teams to arrive in the event of an accident.
If possible, you should figure out well in advance what kind of bivvy bag you need for your trip. It’s always a good idea to have a more breathable bag, especially for shorter breaks. Otherwise condensation can build up really quickly and start dripping onto your clothes or sleeping bag.
The good and the bad
Doesn’t sound very inviting, does it? It rarely is. Bivouacking has many faces. Here are two of them:
The good side
High up on this picturesque ledge under a starry sky, sheltered from the wind in this cosy, lightweight and breathable two-man bag. Snuggled up with your loved one, you can relax and enjoy the peace and quiet of the mountains until you drift off into a blissful slumber.
The bad side
High up on this remote mountain ledge, dark clouds appear out of nowhere and suddenly it starts bucketing down. Now you’re panicking, struggling to get your bivvy bag out from the bottom of your pack in face of brutal winds and rain, sweating into your already soaking-wet clothes. And, the inside of the bivvy bag ends up getting as wet as the outside.
When you’re both finally inside the bag, you have to zip it up completely and crouch down so that the wildly fluttering fabric doesn’t keep hitting your face. It’s moments like these when couples hate snuggling. Plus, despite the protective cover, it seems to keep getting colder, and the air quality is getting progressively worse. In situations like these, it’s important to keep the material at a distance because when it comes into direct contact with you, it will cool you down instead of warming you up. And, since weather is so unpredictable, you have no idea if the storm will have passed a half an hour from now or a half a day. Time to go to your happy place…
Most bivouacking experiences lie somewhere between these two versions. The starry sky will certainly be the rarer occasion of the two because if the sky is clear enough to see and enjoy, you probably don’t need the bivvy bag. In such cases, a sleeping bag will suffice, especially if it provides some warmth and protection from the wind whilst keeping moisture at bay. This is something that a lot of sleeping bags are perfectly capable of doing nowadays.
Even those surprising changes in weather will become rarer with time, considering the fact that we have devices that provide weather forecasts and allow us to plan our adventures in real time. At least this is true for those more moderate adventures in the Alps and Central Europe. However, as long as unpredictable weather conditions and remote areas still exist and people go on physically demanding adventures spanning over several days, our beloved bivvy bags will continue to exist.
What is a bivvy bag and what do I need it for?
Simply put: a bivvy bag is the bag in which you sit or lie when bivouacking.
The simplest version consists of a more or less waterproof top and bottom made of synthetics that is sewn together. The top bit has a slit that allows you to slip inside and serves as an opening for your face. There are bags for one or two people, with the latter having the advantage that it generates more heat and the disadvantage that it is more difficult to use.
A bivvy bag is lighter and cheaper than a tent and makes it possible (at least theoretically) to set up a weatherproof shelter anytime and anywhere. Unfortunately, just having functional clothing is not always enough. When bad weather lasts long enough, water usually always finds a way in. In such cases, bivvy bags can be a life saver.
The basic characteristics of a bivvy bag.
Less expensive bivvy bags can provide acceptable protection from wind and water for shorter periods. However, they cannot withstand the violent gusts of winds and are less resistant to abrasion, so when they come into contact with shoes and other equipment, they won’t last long. Plus, the pressure exerted on the material by sitting or lying on it causes moisture to permeate the fabric surprisingly quickly.
Here you should make sure that the base material has a hydrostatic head of at least 2,000mm (significantly more is better, because the pressure applied to the material can be much greater when you’re squatting).
It is rather difficult to say how much warmth any given model will provide. Why? Well, it depends at least as much on the situation as it does on the model and individual physiological factors. So, no blanket statement can be made here. More important than the strength of the material is the layer of air that serves as insulation between your body and the bivvy bag.
Simple enough, right? Well, things get a bit more complicated when the breathability of the fabric comes into play and with it the coatings, membranes and laminates, which are either on the top, bottom or both sides.
Then, there is an array of other features, including completely closable 3D hoods with mosquito nets and anatomical foot boxes, tent-like pole structures and heaps of other bits and bobs that can be added to the bivvy.
How do bivvy bags differ from one another?
Based on what we’ve talked about so far, it should be clear by now that the perfect bivvy bag has to meet all sorts of different requirements. Unfortunately, there is no such thing as a do-everything bivvy bag. Maybe someday, though!
Until some genius creates this miracle bag, we have to navigate between the following three points when deciding on a model:
- Comfort (breathability, spaciousness, features)
- Low weight and pack size
- Weather protection (Quality of the material, robustness, complete sealability (for lack of a better term))
There is no bivvy bag that meets all three criteria equally. It’s like buying a car. Despite all the high-tech euphoria, you still can’t get a family-friendly and environmentally-friendly hybrid race car.
However, when it comes to bivvy bags, we can at least have two of the three mentioned above: i.e. 1) and 2) or 1) and 3). A combination of 2) and 3) is much more difficult or significantly more expensive, but still feasible.
What materials are used for bivvy bags?
The desired criteria determine the composition of the material and the construction of the bivvy bag. Let’s list the materials first:
The key component of most ultra-light models is a a metallised foil. Such bivy bags may be damaged or unusable even after a single use, but are also intended for emergencies only, similar to a rescue blanket.
The more durable basic models have a tent-like nylon or polyester fabric with a polyurethane coating (PU coating). Nylon, polyester and cotton blended fabrics are not waterproof without such a coating. PU gives the material its functional properties due to its high density and flexibility.
In addition to PU, silicone is also used, which is usually classified as being of a higher quality. Silicone coatings are more elastic, more durable and more expensive than other coatings. They not only increase the fabric’s tear resistance, but its UV resistance as well. They are also significantly lighter than PU coatings with comparable levels of waterproofness.
Bivvy bags with membranes
More elaborate bivy bags also have membranes. You can read more about how they work and what the advantages are compared to a coating here.
If you prefer a membrane, let me say this: in practice, you will notice only minor differences between the different membrane brands when it comes to breathability. As a rule, all technologies reach their limits at a certain amount of moisture and/or temperature distribution.
All coatings, laminates and the like increase the weight and pack size just like any other additional feature. The more protection, versatility and functionality the fabric offers, the more weight you’ll have to carry and the larger the pack size will be. Every other little addition, like more room or covered zips add more weight as well.
Bivvy bag shapes and designs
Most bivvy bags are cut like a slightly larger sleeping bag and lie flat like a blanket. The volume of the bag results from our bodies or other little extras like stiffeners, guying options or small poles.
The latter offers additional headroom, which can come as a welcome relief when sleeping in it for multiple nights in a row. However, the stability of models with this simple frame should not be overestimated. Some can stand upright only when the zip is completely closed, whilst others tilt towards your face as soon as a little breeze picks up. More reliable are the more complex constructions like a criss-cross pole structure. However, so much comfort and weather protection is neither light nor cheap.
An important question you may need to consider is whether the bivvy bag should close completely. After all, there’s no way to be completely protected from the elements unless the interior can be sealed off completely with a strong zip. Drawstrings, hook-and-loop fasteners and vents always leave small gaps and openings, which in extreme cases will have to be facing away from the the direction of the weather.
Oftentimes, that’s easier said than done. However, sealing yourself in to this extent is only for ambitious projects in higher altitudes or colder climates. For most other emergency situations and “normal” bivouacking adventures, you’ll be fine with bivvy bags that can “only” be closed with buttons, drawstrings or the like.
Bivouacking is more than just an emergency solution in adverse mountain conditions. It allows you to experience nature in a way you never have before and is a flexible option between camping and sleeping “completely unprotected” out in the open.
However, bivouacking is not recommended for people who prefer not to be in direct contact with the ground, materials or other peoples’ bodies. But, if you discover the urge to be in the great outdoors and can overcome your inhibitions, you may end up loving it! Then, you’ll venture a little further out, head up to the mountains and realise you need to start looking for the proper bivvy bag! We hope this article will help with that.