| Vapor Barrier Fabrics Properly used vapor barrier bags and sheets can effectively increase the warmth of any sleeping bag. However, the incorrect use of vapor barriers can dangerously decrease warmth, comfort and safety. All of the following options should be completely mastered before heading for the backcountry. A vapor barrier (VB) bag can be used inside the sleeping bag for 10-150 F added warmth. Some people however, find that such bags are uncomfortable. Thin long-john underwear can be worn to keep the VB fabric and any condensed moisture away from the skin. Aninformative discussion on cold-weather vapor barrier use can be found on the Internet at: www.warmlite.com/vb.htm. A VB bag traps body vapor close to the skin and quickly raises the inside humidity to 100%; this then shuts down the body's excessive heat loss due to the evaporation of the always present insensible perspiration from the skin. Once no longer needed to evaporate this perspiration to water vapor, this heat stays in the body and slowly builds up warmth during the night. Of course, using a VB bag also keeps body moisture, dirt and skin oils out of the sleeping bag, thus reducing the need to dry or wash it. Washing the VB bag is much easier than washing the sleeping bag. Use
of a full length VB bag with reflective light-colored fabrics can effectively
reduce convective, radiant, and evaporative heat loss. This simple inexpensive
and lightweight option is an excellent way to add warmth to a sleeping
bag or hammock. |
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