Most often known as “bivy sacks” or the single-man tent, bivouac sacks are simple one-person shelters just big enough to sleep in. While they used to be used for emergency shelter, they now serve many uses and are frequently used by:
- Bicyclists who camp on long cycling trips
- Hikers who travel alone in the backcountry
- Climbers who climb routes that take longer than a day to complete
- People who don’t mind sleeping in snug spaces or are very serious about shedding weight in their packs
Old bivy sacs were nothing more than waterproof shelter, keeping inhabitants dry but offering little in heat protection or ventilating vapor produced by body heat. Today’s bivouac sacks are two tiered layers, the bottom being made of a waterproof nylon and the second is rip-stop nylon usually coated in something like Gore-Tex to keep that layer waterproof but breathable. Gore Tex repels water droplets but ventilates vapor by pushing it out and through the fabric. Unfortunately, in below freezing conditions, occupants can occasionally awaken to a thin layer of frost due to the amount of dampness on the inner walls.
These bivy sacks serve only two basic functions: keep the inhabitant and their sleeping bag dry and increase the warming capacity by 10 degrees. The opening for the head doesn’t offer much in the way of protection unless the drawstring is snugly closed, but this is often restrictive to campers. Some additional amenities in these sacks include:
- Armholes to allow campers to sort gear or cook while remaining inside
- Straps to secure sleeping bags in place and prevent the bag from tangling
- Full-length zippers to allow for several ventilation options
Users of the bivy sack often prefer these shelters to tents because they feel more connected to nature. There isn’t a large shelter separating them from the elements and these sacks give them more of a feeling of sleeping under the stars than a tent would. However, if campers prefer that tent feeling but don’t want to pack a tent and its weight around, there are now two-walled bivy tents, smaller than a tent but heavier than a true bivy sack, weighing in at about four pounds. They offer more interior room while still remaining lightweight, without the occupant feeling constricted or weighed down by a heavier shelter.