Sleeping bags for snow camping should be of a walled construction and filled with duck or goosedown and have a large draw-cord hood. Other points to look for in a sleeping bag are:
- loft—the greater the loft the warmer the bag
- shape/fit—which design best fits your shape, the extent that you move inside a bag, and how claustrophobic you are
- outer material (Gore Dryloft reduces dampness, but is expensive and makes the bag heavier)
- baffle design—smaller down pockets are generally more effective in keeping the down where it is meant to be
- foot design—for mummy bags a shaped foot is likely to improve comfort/ warmth
- zips—let in cold
- draught tubes—stop cold, but add weight.
There are some good synthetic fibre bags on the market that are much cheaper than down bags. They dry much more quickly if wet, but they are generally heavier and bulkier to carry, and they do not seem to last quite so long.
Manufacturers’ temperature guides for sleeping bags are just that—guides. Some seem too cold, others too warm, and people have different insulation needs to feel comfortable. You will need to come to your own conclusions. An inner sheet will make a bag a few degrees warmer, and will prolong the life of your bag by keeping it clean. Cotton is cheaper, silk is lighter and slightly warmer but more expensive.