Information for consumers on the design, use,
maintenance and lmitations of


1 Shell and Lining Fabric
The choice of shell fabric and finishing affects the weight, water repellency, comfort, cost, durability and longevity of a sleeping bag. There is no universal consensus on the best fabric. Often bags will have a tightly woven shell with a DWR (Durable Water Repellent) finish. High thread count fabrics are designed to minimize down leakage and to improve wind resistance. Lighter fabrics may not be as durable or down proof but with careful use may suit your extreme lightweight needs for many years. Cotton is not as strong as nylon and polyester, it absorbs moisture easily, and is hard to dry. Inside liner fabrics are generally a lightweight nylon, usually lighter in weight than the shell fabric.

2 Insulation Materials
The typical insulation materials that are used in sleeping bags include natural fills (down and feathers) and battings of synthetic fibers (hollo fiberfill and polyester fiberfill). These insulating materials are sandwiched between the shell and lining fabrics.
Synthetic insulation is extruded polymers, essentially plastic threads. These threads may be either continuous filament (a single long strand) or short staples, pieces 1.5 to 4 inches long. Either type may be made with hollow threads. The hollow interior reduces weight, and traps air for insulation.

3 Draft Tube
This is an insulated tube running parallel to and alongside the zipper that blocks heat loss through the teeth of the zipper. Otherwise, this area would have a long uninsulated seam running the length of the bag. Depending upon the temperature requirements of the bag, this tube may be thickly insulated, a simple flap of fabric, or absent altogether. For cold weather bag, a filled draft tubes may be necessary .

4 Collar, Draft Collar, Neck Yoke
The collar is an insulated tube covering your throat and shoulders. It may be a flap of fabric or an insulated tube. The purpose of the collar is to prevent heat loss from around the neck. Warm air can be pushed out and cold air sucked in as the volume inside the bag changes. The collar acts as a dam to help slow this loss. Collars are more important on colder weather bags.

5 Shifting Insulation, Amount of Loft
Down bags may be built with continuous baffles, these are uninterrupted tunnels that run from the top of the bag to the bottom. They allow you to fine-tune the warmth of the bag by redistributing insulation from top to bottom and vise versa. However, contnuous baffles can allow down to shift on its own, so periodic shake-ups may be needed. More fill is generally placed into the top of a bag since heat rises and since the insulation value in the bottom of the bag is reduced due to compression.

6 Sewn through seams and Baffles
Sewn-through seams are the easiest, and lowest cost construction for a sleeping bag. The insulation is sandwiched between the inner liner and the outer shell and the seams sewn through all three layers. “Three” and “four” season Down bags are constructed with sewn in baffles. In this case the inner and outer shells are connected by a piece of baffling material that separates the two shells. In that way the insulation keeps the two shells apart throughout the entire length of the bag.

7 Hoods
Up to 50% of your body’s heat can be lost through your head, an effective hood is a weight efficient way of improving a bag’s warmth. Hoods should be able to draw up and close to a 3" opening, provide room for wearing a hat, and should feel comfortable against the face.

8 Foot Box
Better-designed mummy bags are flared and boxed, and have more insulation in the foot area

9 Air space within a bag / Cold Spots
Other things being equal, the more snugly a bag fits, the more thermally efficient it is, since your body will heat a smaller volume between you and your bag. However, the bag must be roomy enough to allow a good night’s sleep. The amount of space needed is a personal judgment.

10 Size and Volume of bag- Length and Width
Sleeping bags with lower internal volume are more efficient since there is less air inside the bag to heat up. First the air inside the bag then the dead air within the insulation must warm up before the bag will begin to insulate. Lower volume bags heat up sooner and insulate sooner.

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