Bivouac & Bivvy Bag: How to Sleep Out Light, Dry and Discreet

What is a bivvy bag and what is a bivouac?

Originally, a bivouac is an improvised, often unplanned night in the open — a climber on a ledge, a hiker overtaken by darkness. Today the word also means a deliberately simple night outside with minimal kit and no tent. The bivvy bag is the key piece: a body-shaped shell that protects your sleeping bag from dew, wind, splashes and light rain, and adds some warmth by stopping draughts.

Most bivvy bags have a waterproof, tough floor (often called a bathtub floor) and a waterproof-breathable top fabric that lets part of the moisture from your body escape. They differ mainly in how the head end is built.

A breathable bivvy is the best all-rounder. An emergency bivvy belongs in every first aid kit as a backup, but is a poor choice for planned nights because it soaks your sleeping bag from the inside. Our sleeping gear guide explains how bag, pad and bivvy work together as one sleep system.

Bivvy vs tarp vs tent: which one when?

None of the three is "best" — each shines in different conditions. The bivvy gives the smallest footprint and the most direct contact with the night; the tarp gives a dry roof and room to cook and pack; the tent gives full enclosure against rain, wind and insects. The wider decision, including hammocks, is laid out in tent vs tarp vs hammock.

The tarp plus bivvy combination sits in between and is a favourite in bushcraft: the tarp gives you a dry roof for cooking and packing, the bivvy protects your sleeping bag from splash, blown-in rain and dew. See tarp shelter setups and our guide to choosing a tarp. If you prefer to sleep off the ground, a hammock is the other lightweight option.

Choosing a spot for your bivouac

Because a bivvy lies directly on the ground, the ground matters more than with any other shelter. Look for level ground that is slightly higher than its surroundings: rain runs off instead of pooling under you, and on still nights cold air flows past you into the hollows below. The general rules for a safe camp are in how to choose a camp site.

In a thunderstorm, a bivvy offers no protection at all: avoid summits, ridges, lone trees and open fields when storms are forecast, and choose a tent or a hut instead. Check the forecast before you go and keep an eye on the sky.

How to set up a bivvy bag

Setting up a bivvy takes minutes — but a few details decide whether you sleep well. Do it while there is still light, especially on your first night out.

Keep your pack close — under the head end of the tarp, beside you with a pack cover, or as a pillow base with soft clothing on top. Water, head torch and a warm layer should be within reach without getting out. On cool nights, the bivvy adds a little warmth; calculate your sleep system for the expected night low with the sleeping bag and R-value calculator.

Condensation in a bivvy bag: why it happens and what helps

Condensation is the biggest complaint about bivvy bags. Your body releases moisture all night, through the skin and with every breath. A breathable fabric lets part of this vapour out — but only when the outside of the fabric is warm enough. On cold, clear, still and humid nights, the outer fabric cools below the dew point, and the moisture condenses on the inside of the shell, or freezes as frost.

Bivvy and tarp: the classic bushcraft combination

A small tarp over a bivvy gives you the best of both: a dry place to cook, pack and get dressed, and a sleeping spot that stays dry even when rain blows in. Because the bivvy protects against splash, the tarp can be pitched lower and smaller than without it. Plan size and pitch with the tarp planner.

Where there are no trees, trekking poles can hold the ridge. On open ground, a low pitch facing away from the wind is more important than a large tarp. More pitches, from lean-to to diamond, are in our tarp shelter guide; the right knots for tarps make setting up quicker.

Bivouacking in the rain: strategy

A good bivvy keeps light and moderate rain out for a night, but it is not a tent: getting in and out, packing and cooking in steady rain without a roof is hard work. Decide before the rain arrives.

If you get your sleeping bag wet in a cold night, the situation can become serious quickly. Keep a dry warm layer in reserve, know how to recognise the early signs of hypothermia, and have a bail-out plan — a car, a hut or a shorter route home. Our guide to fire in wet weather helps where fires are permitted.

Bivouacking in cold weather and in insect season

The bivvy bag is a year-round tool, but the two ends of the season ask different things of it. In the cold, the challenges are ground chill, frost inside the shell and a sleeping bag that slowly gets damp. In summer, the problem is midges, mosquitoes and ticks — and a shell that is too warm to close.

How warm does a bivvy bag keep you?

A bivvy stops draughts and adds a thin layer of still air, so it helps a little — but only a little. The site's sleeping bag calculator counts a bivvy or open bivouac as roughly +1 °C, the same as a tarp, while a closed tent counts as about +3 °C. Plan your sleeping bag as if you slept in the open, and let the bivvy be a reserve, not a substitute for insulation. Wind matters far more: on an exposed spot, a breeze can cost you several degrees, which you can estimate with the wind chill calculator.

Bivouac below freezing

Below 0 °C the ground becomes the main heat thief. Use a pad of at least R 5 for ground around −5 to −10 °C — for example a closed-cell foam pad under an insulated air pad, as explained in the winter sleep system section. Expect frost on the inside of the shell on clear nights; shake it out before it melts. Over several frosty nights, down bags lose loft as moisture accumulates, which is why many winter bivouackers prefer synthetic bags or a vapour barrier liner. If deep snow is available and you have practised, a snow shelter is warmer than any bivvy on the surface. Our guide to layered clothing explains which dry layer to sleep in.

Midges, mosquitoes and ticks

A standard bivvy with the hood open is an invitation to insects. In midge and mosquito season, a bivvy with a mesh insect net over the face opening, or a separate head net, makes the difference between sleep and misery. Avoid still, damp spots near standing water, and choose a site with a light breeze — see insects and camp sites. Ticks crawl up from grass and leaf litter: check your body the next morning and remove any tick promptly, as described in the first aid guide. Keep food in a closed bag away from your head and hang or store it as described in food storage outdoors, so mice and foxes are not tempted to investigate your bivvy at night.

The unplanned bivouac: caught out by darkness or weather

The original meaning of bivouac is the night you did not plan: you got lost, an ankle gave way, or the light ran out before the car park. What matters then is staying warm and dry and being found if necessary — not comfort. An emergency bivvy bag weighs little more than 100 g and belongs in every day pack for exactly this moment.

Your first bivouac: plan, packing list and weight

The best first bivouac is boring: a dry, mild night with a stable forecast (see reading the weather), a known spot within an hour of the car or home, and a bail-out option. Arrive with at least an hour of daylight, lay out your bed first, then cook and eat. Following a simple routine — bed, water, food, then light — is the heart of good camp setup, and it matters even more with a bivvy because you have no vestibule to sort things in later.

Water is easy to underestimate when you camp away from taps: for a summer overnight with dinner and breakfast, around 3–4 litres per person is realistic; the water calculator refines it for temperature and effort. If you plan to refill from streams, bring a way to filter water. Plan cold or simple hot meals — see meal planning for the outdoors.

That puts a complete bivvy-and-tarp sleep system at roughly 2–3.5 kg, often less than a two-person tent plus pads and bags. It fits in a 30–45 litre pack — see choosing a backpack — together with the rest of the essentials on our bushcraft kit list. You can assemble and weigh your own list in the Kit Builder. Good footwear matters too: after a night in dew, dry socks for the morning are a small luxury worth carrying.

Is bivouacking legal? Bivouac vs camping

In many countries, the law distinguishes between camping (with a tent, often for several nights) and a bivouac (a single night without a tent). But the details vary widely, and a bivvy bag is not automatically a legal free pass.

• Germany: overnight stays in the forest and in open country are regulated by the forest and nature conservation laws of the 16 federal states. Whether a bivouac without a tent is allowed, tolerated or forbidden differs from state to state and is often a grey area. National parks and nature reserves are off-limits. Our guide to wild camping in Germany explains the situation in detail.
• Scotland: access rights generally include wild camping when done responsibly, following the Scottish Outdoor Access Code, with local restrictions.
• Scandinavia: the right of public access (allemansrätten and similar) usually allows a night outside, with conditions such as distance from houses.
• Elsewhere: in England and Wales, and in many other places, you generally need the landowner's permission. Always check local rules.

Wherever you sleep out, the same etiquette applies: arrive late and leave early, stay one night only, keep away from paths, houses and wildlife, no fire where it is not explicitly allowed (see fire safety), and take all rubbish with you. A bivouac done well leaves no trace. For more on responsible outdoor skills, see our bushcraft basics, and for cold-season nights, winter camping.