Picking a Sleeping Bag — What is Your Comfort Zone?
By: Mark Mazour
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Sleeping in the backcountry is supposed to be roughing it, but the difference between roughing it and being miserable and roughing it and loving it is as simple as a comfortable sleeping bag.
Sleeping Bag Styles
This difference in sleeping bags is readily apparent. Two main styles are on the market, mummy and rectangular.
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Many different insulation types are on the market. However, the two main types are synthetic (manmade) fibers and down (primarily goose feathers). They each have their benefits, and at times, a combination of the two creates the best option.
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Made from the undercoating feathers of geese, this soft material is an exceptional natural insulator. The secret to its warmth is the loft it provides, trapping air as an insulator. This is also how it is measured - with a number indicating a volume of air that is displaced by one ounce of down. For quality down, look for fill-power values of 600 and greater. This higher loft number indicates a higher purity down that will loft greater when unpacked and provide more warmth.
Down is also a very light material for the warmth it provides, and it is extremely compressible - allowing you to pack a large, warm bag in a very little space. The drawback with down is that it loses its insulation value once it becomes wet. Since it takes a long time to dry in the field, this is a concern if you will use the bag in wet conditions. With a down bag, also look for construction that prevents the down form shifting and bunching up possibly forming cold spots.
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Most synthetic insulations are constructed of a long hollow-core fiber that is layered to trap air and provide insulation. The hollow core fibers are lightweight and have numerous air pockets for better insulating capability. With a synthetic bag, it is a good idea to look for multiple layers that are offset or overlapping. This helps prevent cold spots and blocks air from moving from one layer to another.
Synthetic materials are usually heavier and bulkier than down, and they are not as compressible. That does not mean that they are not for backpackers, though. Unlike down, synthetics do not lose their insulating ability when they become wet. Should they become wet, they absorb very little water and dry quickly, making drying in the field a possibility with a little heat or sunlight. Price is always a consideration, and compared to a quality down bag, a synthetic model will be less expensive.
Size and Weight
In explaining style and insulation, we've already touched on a lot of this. If space or weight is of utmost concern, a down mummy bag is the best choice. It is all a matter of how and when you will use your bag. Look at the various ratings and carry weights to determine what is best for you. Sometimes the best answer is two bags - a compact model for backpack trips and a larger rectangular model for comfortable sleeping on a cot at base camp.
The other factor to look at is length. Commonly, sleeping bags come in two lengths, regular and long. Generally, if you are six-foot-tall and under, a regular length bag will be more than adequate. However, if you are over six-feet-tall, you may want to look at a long bag for extra comfort.
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Outershell Material
Depending on the use of your bag, you may want to look at the outershell material. If rugged field use is on your plans, you want a shell material that can stand up to it. Heavy cotton canvas works well for rectangular outfitter bags, but with its weight and stiffness, it does suit a packable bag. Then, synthetic material such as ripstop nylon or Pertex is a better choice for increased packability, while still maintaining excellent durability.
If you plan to sleep outside with your bag, you will want a shell that is at least water resistant, to protect you and your bag from light moisture. DuPont Tactel and Gore Dryloft are two materials on the Market that will give you water resistance. However, with all the stitch lines in a bag, it is hard to make it completely waterproof. If sleeping outside in inclement weather is in your plans, a weatherproof bivy sack or shelter is your best option.
Temperature Rating
This is the one measuring stick used to differentiate between bags. Bags all differ in fill weight, fill type, size, and style, but every one has a temperature rating on the tag. What does that mean to you?
The temperature rating is derived as the lowest temperature that the average person can tolerate and still remain comfortable within the bag. Most manufacturers try to maintain similar methods in establishing temperature ratings, but you should know that no standard has been fully accepted industry wide. Therefore, variances do exist from manufacturer to manufacturer.
The other variance that exists is "the people factor." Above, I mentioned this "average person." When speaking about thermal comfort, it is hard to find an average person. Rarely will you find two people in the same room that agree on a temperature that is right. A good example is in our office space; whenever I think it is finally cool enough in here, others are turning on their space heaters because they are too cold.
Some Other Things to Think About
Before selecting a rating, first determine the coldest temperature at which you will be using the sleeping bag. Remember that this is only an estimate. You can't always predict what the weather will be on next week's camping trip, but you need to start somewhere. Also, women tend to be a bit more sensitive to the cold than men, so women should usually try to err on the colder side with their estimate. It is also a big help to know how you view temperatures in regard to other people. I usually run a bit hotter than the rest of the crowd, and most temperature ratings for bags seem to be right on for me.
If you camp in warmer conditions than your bag's rating, you will have to ventilate it slightly. Most incorporate two-way zippers that allow you to zip up and still ventilate portions of the bag, especially the footbox, to release the excess heat. If it is really warm, you can also leave the bag unzipped, and you will definitely want to loosen all the drawstrings on mummy bags.
That one is simple - YES! Picking a bag that is too warm will cause you misery in the long run. Whether at home or camp, I always sleep better if I can remain under the covers. If you pick too warm of a bag, you will be forced to endure a long night alternately sweating and freezing as you throw the top layer back and forth.
When I first started backpacking in college, one guy I hung out with always had the most "extreme" gear, stating that "you never know what will happen." So, preparing for the worst, he obtained a minus 30-degree bag. The hole in his theory was that most of our camping was under summer conditions and temperatures never dipped below 40 degrees. I just laughed as his bag turned into an expensive sleeping pad since he was forced to sleep on top of it every night.
For me, a 15-degree bag is just right for all my three-season camping needs. I can vary what I wear to bed and adjust the zippers and hood drawstrings to make it fit nearly every situation. I have only been cold in the harshest winter conditions where the temperatures approached 15 degrees. If you plan on camping in all four seasons, the best solution is to purchase two separate bags. Pick up a heavy winter bag for the cold times, and then use a lighter, three-season model for the rest.
When searching for your sleeping bag, there are several other questions to ask to help refine your bag selection.
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If you get a little claustrophobic, you may want to look for a warmer bag to compensate for the additional heat loss. If you are still against mummy bags, another solution is a light fleece hat to wear to bed, preventing the major heat loss from your head.