November 10, 2010
When I’m traveling by bicycle, I like to keep camping as simple as possible. Especially when I’m traveling alone, I try to maximize my time on the bike and minimize the time I spend doing “camp chores.” For this reason, I usually opt to eat sandwiches over cooking an evening meal, don’t usually build fires, and don’t like to spend time constructing elaborate shelters.
However, when traveling as light as possible is also your goal, it can be difficult to find a lightweight shelter that doesn’t require extensive staking or outside objects — such as trees and poles — to erect. Also, commercial lightweight shelters — such as tarp tents and Megamids — generally leave out what I consider the most important part of a shelter: a solid barrier between me and the cold, wet ground. I could carry the necessary ground cloths, bug nets, hiking poles and stakes needed to erect these shelters. Or, I can just sleep in a bivy sack.
A bivy sack is a thin waterproof shelter designed to slip over a sleeping bag, protecting the bag and the person inside from the elements. You just throw it on the ground, stuff your sleeping bag and mat inside, and you’re ready for a night of sleep. Some bivy sacks come with a single pole to hold the end of the bag away from the sleeper’s face. The simplest versions are little more than nylon bags that provide insulation against wind chill and rain. This is the version I prefer to use. I have a Black Diamond Winter Bivy made out of water-resistant Nextec fabric that weighs a mere 9 ounces and packs to the size of a burrito. I have snuggled up inside my bivy in a range of conditions, including winter camping in 35 below zero, a 60-mph windstorm, and a light rainstorm that lasted the entire night. The sack has proved itself to be a great barrier from the elements, durable, and in its own way comfortable (bivy sacks are cozy but they don’t favor the claustrophobic.)
The drawback to bivy sacks, besides confining the sleeper to a small space, is unavoidable condensation. Breathable waterproof fabrics such as Gortex help reduce the amount of moisture that builds up inside the sack, allowing humidity to pass through while also holding out moisture from outside. Another solution is to use a vapor barrier liner, which keeps humidity from penetrating the sleeping bag.
Bivy sacks can also become a drag if you’re forced to spend a longer period of time hunkered down, such as waiting out a storm. Plus, all but the most waterproof (and therefore non-breathable) bivy sacks can’t hold out heavy rain. When I’m facing the possibility of a larger storm, I pack a small tent. My Big Agnes Seedhouse SL 2 tent weighs in at 3 pounds 6 ounces and easily dangles from my handlebars on my pannier- and trailer-free bikepacking set-up. If you don’t require a floor (as I mentioned earlier, I like my shelter to be completely enclosed), you can set up the fly alone and pack as little as 2 pounds, 2 ounces of waterproof shelter. Plus, this tent can cozily fit two people, which makes it a good option for trips with a friend.
Of course bivy sacks aren’t for everyone, but for simple, lightweight sleeping solutions, there’s really nothing better.
Photo by Jill Homer. Photo caption: Cozy quarters -- prepping for a night of winter camping with bivy sacks.