Staying warm at night is important not only for comfort, but also for safety. Hypothermia is a very real risk if you are sleeping in a cold environment without heat. Sleeping bags or warm blankets along with layers of warm clothing can make the difference between being comfortable and dangerously cold. As nomads, many of us travel with the weather to avoid extremes, but what do you do when the weather turns unexpectedly cold and your gear is not adequate?
This situation actually happened to me in the fall a few years ago as I was camped above 7,000 feet near Flagstaff, Arizona. The days were still nice, but the nighttime temperatures started dropping into the 20s. Since my sleeping bag was designed for warm weather, I was suddenly unable to keep warm at night, even wearing several layers of clothing. The worst part was that my feet were cold all night no matter what I tried.
I hit upon a crazy idea one night as I was in bed trying to stay warm. Why not line the sleeping bag with a scrap piece of Reflectix that I had in the trailer? The next day I slid the Reflectix into the sleeping bag toward the bottom. That night I slept comfortably, even though the temperature was still only in the 20s.
Reflectix is an innovative, reflective insulation material that is manufactured by Reflectix, Inc. The material is thin and light, but works surprisingly well. Essentially, Reflectix is a layer of plastic bubble wrap sandwiched between two layers of foil. Despite being thin, it does a great job of reflecting heat. Whether you want to keep heat in or out, this material is amazing for its weight and density.
Using Reflectix as a sleeping bag liner helps to keep body heat inside the sleeping bag so you can stay warm. This is a simple and inexpensive way to sleep warmer at night when the temperatures drop.
Since Reflectix does not breathe well, you should use some caution to avoid condensation buildup. Moisture in your sleeping bag or clothing will lead to rapid heat loss. Using a single layer instead of wrapping it around you will help avoid condensation. It may also be worth taking it out and opening the sleeping bag to air out during the day if you are concerned about condensation.
Ultimately, it is preferable to have the right gear so that you do not need to resort to tricks like this that might introduce condensation problems. In a pinch though when you are caught off guard by a sudden change in the weather, this trick may make a significant difference in being able to sleep comfortably.