There are basically two types of insulation used as fill in backpacking sleeping bags—each with their pros and cons. No bag will be perfect for every situation, so it is important to determine what your primary uses will be and buy accordingly.
Goose and Duck Down
- Lightest warmth per weight ratio
- Most comfortable and breathable fill
- Comfortable over a larger range of temperatures because of breathability
- More compressible and much longer-lasting than synthetics if properly cared for
- An excellent choice for desert conditions and/or when using a reliable shelter
- Worthless at insulating once it gets wet (it flattens when wet and loft is what is necessary for insulation)
- Takes forever to dry once wet—forget about it on the trail!
- Requires special care for cleaning. Be sure to use knowledgeable cleaners or launder with down soap and dry thoroughly with special care to not tear interior baffles.
- More expensive for an initial purchase but lasts longer
- Insulates even when wet
- Dries quickly
- Less expensive than down
- Wash and dry at home without much in the way of extra care
- Not as breathable or comfortable a range of temperatures
- Heavier and less compressible
- Not as long-lasting as down
Synthetics are made from polyester—the same material used in the leisure suits of the seventies! It is very easy to care for but doesn’t breathe as well as the natural fibers. Because of this, synthetic bags can feel clammy and are not as comfortable over a large range of temperatures as down bags are. But they definitely have their place in many backpacks. Different conditions call for different strategies. Synthetic bags are perfect for wet conditions—conditions that you would encounter during a canoe or sea-kayak trip or in really wet weather. Synthetic materials don’t absorb water and mat down; therefore they hold their loft and ability to retain heat even when wet. Once synthetic bags do get wet, they dry quickly. They are very easy to care for-just throw them into a front-loader machine, then the dryer for one cycle. Use a mild soap rather than a detergent.
Down is much lighter and more compressible than synthetic materials. It has a greater warmth-to-weight ratio than synthetics. This means you can get a lighter weight bag and it will keep you as warm as a synthetic bag that weighs considerably more. It can also be compacted into a smaller space, which is very important when you have an internal frame backpack and the bag is carried on the inside. Down bags are much more expensive initially than synthetic bags, but since they last as much as four times longer, they are cheaper in the long run.
The main problem with down is that it is useless when wet. Loft, or trapped warm air, is what actually keeps you warm, not the weight of the fill. Down is very absorbent, causing it to mat down when it gets wet. It also takes a long time to dry. It is useless as insulation once it gets wet; therefore, you must always use some kind of shelter to protect the bag. Even in dry conditions, your body produces some moisture and on trips, you should air the bag daily to dry it out.
Down also requires special care when it comes to cleaning. Follow the manufacturer’s cleaning instructions carefully. If you take your bag to dry cleaners, BE SURE that they specialize in cleaning down. I had a friend who had a North Face Blue Kazoo down sleeping bag, which he brought to a cleaner who had said they knew how to clean down. From the time he got it back, it never lofted very well again. It was obviously not cleaned properly. Because of his experience, I don’t trust the cleaners and will launder them myself.
To launder your bag, be sure to use down soap, usually available at the store where you purchased your sleeping bag. Laundering your sleeping bag is a time-consuming process. Always wash your bag in a front-loading machine. The agitator motion in most washing machines can easily rip the baffles inside of your sleeping bag. The baffles are pieces of material that stabilize the down and keep it from settling. It will take several hours to fully dry your bag—more or less depending on the humidity of your location. It’s a good idea to put a tennis shoe or some other object in with it to help break up the clumps of down so it can dry faster and more effectively.
Some of the important features to look for in a wilderness-worthy sleeping bag are:
- A sleeping bag that fits your body, both in its width and length. A mummy-shaped bag is the best choice for backpacking. The reason for this is because a mummy is made to fit the contours of your body without a lot of wasted weight. Not only does it help reduce the weight of the sleeping bag, but it also makes the bag more efficient for your body to heat, minimizing the cold spots. Don’t go too far in the other direction and get a bag that is too small and uncomfortable.
- A two-way zipper with a draft tube to prevent cold air from coming through the zipper. This allows unzipping from either end to provide better ventilation.
- An insulated hood that is shaped and can be pulled around your head with a drawcord, preventing heat loss through your head. It is also very helpful to have a draft collar at the base of the hood so you can tighten the bag around your shoulders without having to tighten the hood.
- Good insulation in a shaped foot box. Some manufacturers also have a durable nylon lining in the foot box so you can put stove fuel or other items that need to be kept warm inside with you.