It’s plain and simple – a bivy or bivouac sack is only a weatherproof cover for your sleeping bag equipped with a breathing hole. Just like any other type of light equipment, bivvies are specialized pieces of gear. And they also require you to go light and set your priorities. Because anything you add to your bivy sack will add weight.
While bivy shouldn’t be considered a replacement for a tent, because of their limited functionality, they do provide a certain level of protection. But, is a bivy an adequate waterproof barrier, or do you need an extra layer of protection, like a tarp?
According to many experienced campers and hikers, the bivy + tarp practice is a remnant of a time before DWR fabrics, when water-resistant down was considered standard. With new Argon layers, it becomes redundant. Although bivvies work great with tarps since they keep it on top of you and block the drafts at the bottom edge (not a significant benefit for a sleeping bag), often you may find that you need only one of them.
Read our article to get the idea of bivy/tarp symbiosis and whether you actually need a tarp with a bivy.
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What is a Bivy Sack?
Bivy or bivouac sack is a single-person camper’s gear designed as a lightweight emergency waterproof protection for sleeping bags. When they were first introduced to the market, bivvies were a sort of waterproofed nylon slipcovers for sleeping bags.
A bivy sack is solid protection from rain, and not quite good when handling vapor and condensation. Basically, it’s a sack that you pull over your sleeping bag, intended to protect you and your stuff from the elements.
The bivy consists of two tiers
The bottom tier is typically manufactured from a durable grade of nylon with a urethane coating which makes it waterproof.
The top tier is usually manufactured from ripstop nylon and treated with a breathable, waterproof laminate.
If your budget allows it, you may find it more in line with your requirements to purchase a tent-like bivy. They come with an expanded area of shielded headspace and a full enclosure to protect you from weather and insects which can be of use to you when bivvying in the rain. This is what made bivvies extremely popular, especially with hikers.
A bit larger than your sleeping bag, bivvies come in various styles. There are traditional, ultra-minimalist bivy sacks (i.e., Pro Bivy and E-Bivy manufactured by MRS), which are lightweight and fit for utilitarian travelers. On the other hand, you may consider somewhat weightier full-featured bivy shelters. They come with full-length zippers and an internal pole for expanded headspace giving you a feeling similar to that of sleeping in a tent.
Is Bivy the Right Choice for You?
Before deciding whether a bivy is an adequate choice for your outdoor adventure, you need to consider a couple of factors. They include bugs, condensation, the limited space, and the forecast. Based on your preferred type of adventure and the level of comfort you need, you should be able to pick the right bivy.
A bivy sack may be a great solution for you if you’re a fan of fast and light travel, and if used under the right conditions. A bivy allows you to move fast and is an extremely efficient shelter if you prefer traveling without high volume packs. Especially if you don’t mind trading the comfort of a tent for the advantages of a lighter load.
Bivy sacks are a preferred choice for alpine climbers for squatting during multi-day missions and in places where tents cannot fit in sleeping ledges. However, bivy sacks have become increasingly popular with thru-hikers, backpackers and fast packers, and adventurers. Namely, those who prioritize minimalism coupled with weather protection.
Unlike tents, bivvies do provide a certain level of freedom. They make you closer to nature and require a genuinely minimalist mindset.
If you’re far from a Spartan mindset, bivy sacks and shelters may be too cramped for you. True, a tent can provide a much more comfortable, spacier experience, but a bivy is giving you a unique perspective on your environment and allows you to interact with nature more intensely. And you’re also protected from bugs and rain. On the other hand, if tight spaces don’t tackle your fancy, a bivy may be too uncomfortable for you, in which case you should opt for a tent.
The Downsides of Camping in a Bivy
Air circulation in a bivy may be something all campers are bored with. This is also when the usage of tarps with bivvies marches in. And whether you need a tarp at all. With breathable bivvies, manufactured from waterproof laminates like Gore-Tex®, it is possible for moisture produced by your body heat to evaporate through (and out of) the fabric. And it typically works in dry and cold conditions.
If camping in the rain, you should have enough zippers and overlapping material to avoid zipping them shut completely. You can control the interior humidity level by manually venting a zipper or flap. A tarp hanging over your sleeping system may be a good point to consider.
Condensation is undoubtedly a factor with a bivy, given that it’s sort of a single-wall tent. When your body produces vapor, it escapes and mixes with colder air. At one point, the moisture becomes too heavy to be carried by air and starts collecting on the inner wall of your bivy. This is important as you may wonder whether a bivy is capable of maintaining your sleeping bag dry.
If you use Gore-Tex fabric, it may feel damp when it touches your skin, but it actually handles the moisture sensationally. Coupled with good ventilation, it can really help you minimize condensation.
The Pros of Using a Bivy
- Lightweight – The most minimalist of bivvies weigh just a few grams. Some of them, designed to meet the needs of professional alpinists and big-time adventurers.
- Packable – on the account of their ultra-compact nature, bivvies are a great ally when minimizing weight. You can stuff them into your backpacking bag or small alpine pack.
- Sleeping spaces – bivvies just work tremendously for any technical terrain, because all they require is the space to place your sleeping system. This may include climber’s nooks, rock ledges, narrow backcountry spaces, or snow caves that are not spacious enough to stake out a tent. Bivies are also a great way to experience sleeping under the stars.
- Warmth – Compared to tents, bivvies seem to be trapping in warmth far more efficiently. If you opt for any of the top-notch, breathable, water-resistant, ripstop nylon shelters, you’ll have a top layer that can help you stay dry and reduce condensation. They’re especially comfy when the weather is fair, but provide little protection if you’re caught up in a storm. On the other hand, bivies add extra warmth during high-pressure systems in spring and autumn. And if you add a tarp to your bivy arrangement, it may significantly expand your forecast options and make it possible to travel lightweight.
- Efficient – if opting for a bivy, you are free from the hassle of pitching and setup. It also allows you to move faster, as there’s no need to assemble or take anything down. It leaves you with plenty of energy to engage in something more fun.
- Immersion in nature – tents may provide an extra layer of protection, but they do cut off your sense of place, whereas bivy camping allows you to enjoy being out in the open more intensely and with fewer restrictions.
Tips for Bivy Camping
Against the beliefs of most tent-aficionados, bivvying doesn’t have to be tiring and allows you to maintain warmth relying solely on your own resources. If you plan carefully and do the necessary preparation, a bivy can be an awesome adventure, combined with stunning views and a great time with your companions.
We have prepared for you a set of tips for a pleasant night in the mountains:
- Make your bivy site is in a nook – ideally, surrounded by rock walls.
- Make sure you’re not setting down in a small water channel.
- Keep the gear that needs to be kept warm at the foot of your sleeping bag.
- Take off/replace your wet clothing before you go to sleep.
- If the night is cold, use a bottle of hot water for instant warmth
- Avoid cooking close to your sleeping site.
- To prevent condensation from forming, avoid breathing inside the bivy, and use bivy’s hood instead
- Try wearing a face mask – a balaclava or buff for extra warmth
- Air out the bivy during the day
- Use ultralight tarps if you’re camping in the snow to get an extra insulation layer
- Consider bringing a backpack liner/cover to guard against precipitation
- Pick a water-resistant sleeping bag for extra protection.
- Even though you can bivvy in the rain, always check the forecast.
What’s Tarp Got to Do With a Bivy?
It’s mainly down to your goals and priorities whether you’ll opt for a bivy or the room-fitting comfort of a tent. If you opt for a bivy, there are a set of factors you need to consider to ensure you’ll stay dry and as comfortable as sleeping under the stars (often on bare rock) can be. In this article, we have explained the philosophy behind the usage of bivvies, their main characteristics, and the pros of using them.
Most notably, bivies are spatially restricted, tend to develop moisture (condensation), and are not great at protecting your gear.
Many campers and hikers carry a bivy and a tarp but use them both only if the weather conditions are tough (when a storm hits or when it’s really cold). Basically, if the weather conditions are favorable, you don’t need a tarp for the bivy.
On the other hand, due to the development of moisture, bivvies can be quite stuffy (but also warm), which is when a tarp may come in handy and provide an alternative shelter solution for nice weather. In the same manner, you may ask whether you need a bivy with a tarp.
Except for extremely cold weather, sleeping under your tarp in your sleeping bag with no bivy may just save you from tons of condensation and waking up in a damp bag. Your sleeping bag will probably be drier when you get up in the morning than when you go to sleep, even if it’s raining.