This video identifies five things that you should consider when looking for a sleeping bag:
- Warmth - Consider how cold it will be on most of your trips, then go at least ten degrees colder...unless you sleep cold. If you sleep cold, consider dropping the temperature more.
- Features - Zipper length can vary. Do you want pockets or extra drawstrings? What makes the most sense to you?
- Shape - Most mountaineers and climbers will want a mummy bag. These decrease dead air space and increase efficiency.
- Insulation - There are two types of insulation, down and synthetic. Down fill is warmer and more compressible, but it doesn't work well if wet. New technology may be changing this dynamic. Synthetic bags are heavier and may be better for wet conditions...
- Try it Out - Make sure the bag fits. Can you operate it effectively? Can you reach the drawcords and zippers...?
The preceding five questions are a good start. But they're not the end of the equation. Most mountaineers have a quiver of sleeping bags. I personally have two workhorse bags, but many people have more.
First, I have my moderately cold bag. This is a 10-degree down bag that I use when I'm actively mountaineering, climbing or hiking in the snow. And second, I have my 40-degree lightweight bag. I use this for summer climbing and backpacking. This second bag is quite small and light...
Many guides also have an arctic bag. This is a -20 to -40-degree bag that is designed for high altitude-cold weather trips. These bags are specifically designed for places like Denali, Everest or Antarctica. Some guides use a heavy bag and a lighter bag together to create a "Denali Bag."
And finally, most guides also have a bivy sack. This is a very light sack that only provides 10 to 15-degrees of additional warmth. This can be used in conjunction with a sleeping bag or completely without one for super light -- but cold -- ascents.
Some bags have vapor barriers on the outside. I'm not a big fan of that. I commonly use my sleeping bag as a drying machine and any type of barrier on the outside will trap water inside. As I currently use down bags that are not water resistant, I don't want any water near my body.
About the use of "old down..." It's important to note that while this is a lightweight and extremely packable option, it is a risk. If you elect to go this way, you should be very careful with your sleeping bag. It should never ever get wet...
There's a lot more to think about when it comes to the right bag for the right job. Consider this a primer and ask your favorite shop employee or mountain guide what he or she thinks is right for you...
--Jason D. Martin