Sleeping bags are insulated bags intended to keep one warm, particularly while sleeping outdoor or in a tent. It should keep you warm, but not cause you to overheat, while also allowing moisture to escape the bag.
There are many factors to consider when purchasing a bag. You should consider the conditions it will be used in, hot or cold, wet or dry, rough or easy, etc... Then assess each feature of a prospective bag to meet your needs.
Shells are the protective outer material of sleeping bags. They keep out wind and water when not in a shelter as well as protect the inner materials.
- Polyester/Nylon Taffeta is the most common shell. It is inexpensive, light, durable, and offers some protection from wind and water.
- Gore-Tex offers excellent water-resistance and is quite tough, but doesn't breathe as well as other shells
- Dry Loft offers exellent protection from wind and water while being very breatheable.
"Fill" is the insulation that makes sleeping bags warm. When considering bags you will have to consider goose-down or one of the many synthetic available. You will also want to make sure that the fill is well distributed and doesn't tend to clump in specific areas.
- Down, made from the light, soft, warm feathers of geese is a well established fill material. It is very light weight, compact, and warm. It does require some maintenance such as regular drying. If it gets wet it will lose nearly all its insulative abilities.
- Synthetics are generally lower maintenance and less expensive than down while also drying faster and being warmer when wet. Synthetics also provide less warm for a given volume making it bulkier and heavier than down.
It is important to get the correct size when selecting a bag. It should be large enough to leave some extra room for stretching, this will make you more comfortable and prevent compression of the insulation. If you buy a bag that is larger than this you will have to carry the extra weight and it will require more enegy to heat.
- Mummy bags are tapered from shoulder to food and have a complete hood. The more efficient in terms of weight and warmth that other design. If you tend to move around in your sleep or feel constricted in small spaces, a mummy bag might be too restrictive.
- Rectangular aren't as efficient for warmth due to the lack of, allowing heat to escape, as well as a larger volume to heat.
- Semi-rectangular bags are a compromise between mummy and rectangular bags. They have a less extreme taper from head to toe, providing more room that a mummy bag while still being more efficient than rectangular bags.
Hints & Tips
Wet or Damp Bags
Sleeping bags are far less effective when wet. Make sure that you protect then from water by keeping them in a water-proof bag or compression sack. It also helps to hang dry your bag outside your tent after you have slept in it if possible.
Shaking and fluffing your bag before and after sleeping in it will extend the life of the fill, especiall down, making it stay warmer longer.
Don't store down bags in a compression sack, but rather hang them up to make sure their fill stays fluffy and thus warmer.