Bivy Sacks, also known as bivouac sacks, are small, lightweight, waterproof, shelters that work well as emergency survival shelters. I consider bivy sacks to be an essential survival tool that everyone interested in survival needs to have in their arsenal of survival gear.
They were first developed for the mountaineering and ultralight backpacking folk who are always on the lookout for lighter, more compact gear. Originally, they were little more than waterproof bags that fit over sleeping bags to give them more protection against the wind and rain.
It didn’t take survivalists long to realize how perfect bivy sacks are for survival situations. They provide immediate shelter from the wind and rain and can slow down heat loss significantly. Several bivy sack manufacturers now make emergency bivy sacks solely for survival and other emergency situations.
Advanced Bivy Sack Designs
Bivy sacks have been going through quite a few advancements over the last couple of years. There are versions of bivy sacks now that have high tech breathable fabrics such as Gore-Tex and the even more breathable eVent fabric. Theses fabrics help eliminate condensation problems that the early bivy sacks were famous for.
Some bivy sack manufacturers have also begun incorporating more tent like aspects into their bivy sacks, such as a bug screens and arched poles at the entrance that create a self-supporting hood around the facial area. These more advanced bivy sacks are sometimes known as bivy shelters or bivy tents. They are much more expensive than an emergency bivy but will give you a less claustrophobic nights sleep without annoying, biting insects bugging you. They are also more durable than the emergency bivy sacks. When the weather gets wet they can be zipped up to help keep the rain off of your face.
Here is a good video showing a more advanced bivy shelter being set up.
Bivy Sacks vs Mylar Blankets For Survival
All bivy sacks are better suited for survival than their cousins the Mylar space blanket. Bivy sacks do take up a little more room and weigh a few more ounces than space blankets, but they provide better overall protection from the elements and are more durable. Mylar blankets are notoriously easy to puncture and tear, and are often only good for one use.
Bivy sacks, on the other hand, are puncture and tear resistant. They reflect up to 80% of the body heat just like the Mylar blankets do, but do a better job of protecting the entire body from exposure. Some of the cheaper models will tear after extended use, but they will take some abuse before doing so.
Bivy sacks are important pieces of survival gear that will work well with all survival kits, vehicle kits, camping gear, and backpacks. You can still use them as they were first designed– as a shell that goes around a sleeping bag for lightweight camping or mountaineering. On the other hand, they also make good survival shelters– with or without the sleeping bag. They are lightweight, compact, and will create a highly effective survival shelter that will help protect you from the elements in an emergency.