What is a bivvy bag?

What is a bivvy bag used for?

A bivvy bag is used to keep a sleeping bag dry and out of the wind when you sleep outside without a tent. You lie inside your sleeping bag, inside the bivvy bag, directly on the ground or on a mat.

The word is short for bivouac, a basic overnight camp with little or no shelter, which English took from French in the 18th century. Walkers, climbers and wild campers use bivvy bags when they want the lightest possible shelter, or a pitch too small or rocky for a tent. A bivvy bag also works as an extra layer inside a tent or bothy on a cold night.

How does a bivvy bag work?

A bivvy bag works as a waterproof, windproof outer layer around your sleeping bag. The top fabric sheds rain and blocks wind, and on breathable models it lets some of the moisture from your body escape.

The base is usually a tougher waterproof fabric, like a tent's groundsheet, because it sits on wet ground under your weight. Most bivvy bags close around the head with a drawcord or zip, and many have a mesh panel to keep insects out on still summer evenings.

What are the types of bivvy bag?

The three main types of bivvy bag are a simple waterproof bivvy bag, a breathable bivvy bag, and a hooped bivvy bag.

A simple bivvy bag is a waterproof sack. It is cheap and light, and it traps condensation. A breathable bivvy bag uses a waterproof, breathable fabric on top, so less moisture builds up inside. A hooped bivvy bag adds a short pole or two over your head, holding the fabric off your face so you can read or look out when it rains; it sits between a bivvy bag and a small tent.

Emergency bivvy bags, the foil or bright orange plastic kind carried in a first aid kit, are a different item. They are made for surviving an accident, and they trap so much condensation that they are no substitute for a camping bivvy bag.

Browse our bivvy bags range.

Should you choose a bivvy bag or a one man tent?

Choose a bivvy bag if the lowest weight and smallest pitch matter most, and a one man tent if you want shelter to sit up, change and cook in. A bivvy bag is lighter, packs smaller and fits on smaller pitches; a tent gives far more shelter from rain, room to sit up and change, and a porch for wet kit and cooking.

On a clear, dry night a bivvy bag lets you sleep under the stars with almost nothing to pitch. On a wet evening you get into it in the rain, and you get out of it in the rain the next morning, so there is no dry space for changing or packing. Most first-time wild campers are happier in a tent. Our guide to one man versus 2 man tents covers tent sizes, and the one man tents range is here.

Many bivvy campers pitch a small tarp overhead in bad weather, which gives some of a tent's shelter for a little extra weight.

Do bivvy bags get condensation?

Yes. Bivvy bags get condensation because your body releases moisture all night, and it condenses where warm, damp air meets the cold outer fabric.

Breathable fabric reduces this, and a hooped design helps by holding fabric away from the sleeping bag. Leaving the head opening partly open helps most of all. A synthetic sleeping bag copes with some damp better than down, which loses much of its warmth when wet.

Waterproofing is stated as a hydrostatic head in millimetres, the same as tent fabrics. Our hydrostatic head guide explains what the figure means.

What do you need with a bivvy bag?

With a bivvy bag you need a sleeping bag, an insulated sleeping mat, and a plan for rain, such as a small tarp or a waterproof bag for everything else you carry.

The mat can go inside the bivvy bag or underneath it. Inside keeps it from sliding away in the night; underneath leaves more room. Either way, its R-value matters as much as it does in a tent, as our R-value guide explains. See the full wild camping kit list for everything else.

Where can you use a bivvy bag in the UK?

You can use a bivvy bag wherever you can wild camp: on most unenclosed land in Scotland under the Scottish Outdoor Access Code, on the Dartmoor Commons where backpack camping is allowed, and elsewhere in England and Wales with the landowner's permission.

A bivvy bag is less visible than a tent, which is a courtesy to other walkers and does not change the law. The wild camping hub covers where you can camp in more detail.