Bivouac sack

From Wikipedia, the free encyclopedia

This article does not cite any references or sources. (April 2007)
Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed.

A bivouac in winter at Benediktenwand, Germany.

A bivouac sack, bivy, bivy sack, bivi bag or sometimes, in the UK, Emergency Sack or Survival bag, is an extremely lightweight, waterproof alternative to traditional tent systems. It is used by climbers, mountaineers, hikers and minimalist campers. A bivy sack at its barest is a thin waterproof fabric shell designed to slip over a sleeping bag, providing an additional 5 to 10 °F of insulation and forming an effective barrier against wind chill and rain. A drawback of a simple bivy sack is the humidity that condenses at the inner side leaving the occupant or the sleeping bag moist. Better bivy sacks consist of Gore-Tex (or a similar breathable fabric) to allow the humidity to pass.

Very similar is the swag, very popular in Australia.

Rock climbing bivouac in Yosemite National Park

Nowadays there also exists the bivouac shelter or "bivy shelter", a compromise between bivy sack and single-person tent. Using hoops or poles, a bivy shelter is usually supported along its length just enough to keep the fabric off of the occupant, and especially to provide some additional breathing room around the head.

In contrast to a bivy shelter, a traditional bivy sack typically cinches all the way down to the user's face, leaving only a small hole to breathe or look through. Many campers gladly accept the increased carrying weight of a bivy shelter for the huge increase in comfort it affords. However, the traditional bivy sack certainly still holds its place among mountain climbers and backpackers, and is frequently carried on long or dangerous hiking or hill walking expeditions and high mountain climbs as a compact emergency shelter.

In the UK, Bivy shelters have become very popular amongst coarse fishing and large Carp fisherman, who, in pursuit of their quarry, fish throughout the night. This upsurge in popularity has increased competition amongst manufacturers and designs have become more advanced.

An alternative spelling is "bivvy".