There’s nothing worse than camping out in the winter in a sleeping bag that isn’t able to keep you warm. When it comes to winter camping, sleeping bags should actually be rated for lower temperatures than you’ll be camping in. For instance, if you’re going to be sleeping out in temperatures of -15 Fahrenheit, it’s a good idea to use a sleeping bag that’s rated for -30 Fahrenheit temperature.
Sleeping bags are made of several different types of insulation, such as Primaloft, down, Polarguard, Microloft, and Qualofill. The best types of bags are those that are mummy-style and come with a hood. The bag should also come with a draft tube alongside the zipper as well as a draft collar placed at the neck.
The sleeping bag should conform well to your body. If it’s a bit too big, there will be spaces where convection currents can get into and these will make you cold. If the bag’s too big, you’ll likely have to wear some extra layers of clothing to help fill in the empty spaces.
Expedition sleeping bags are good as they’re rated to -30 Fahrenheit; and three-season bags that are rated for 0 Fahrenheit are fine if you augment them with a vapor barrier liner as it can add about another 5 to 10 degrees of heat. You can also use a summer sleeping bag over top of your mummy bag to keep you warmer.