It's your first night on your long-awaited camping trip and you're dog tired. It took all the energy you could muster to pop open that can of beans, fire up your stove, and replenish your aching body with much-needed calories. Gratefully, you crawl into your tent and slide blissfully into your sleeping bag. Rest at last. Hiking over the big pass tomorrow doesn't seem quite so impossible. Until you wake up in the wee hours of the morning, teeth chattering ferociously, toes like Popsicles, and the rest of your body feeling as frozen as a side of beef in a meat locker.
Getting cold in the middle of the night, or so hot and sweaty that you can't sleep, doesn't necessarily mean you didn't buy a good sleeping bag. More likely, you just bought the wrong sleeping bag. Since there are literally hundreds of models of sleeping bags available, perhaps even thousands, this happens more often than you would think.
While it is always important to consider how you plan to use equipment, sleeping bags tend to be more of a general-purpose general purchase. However, if you are planning on serious winter camping (in very cold weather) or mountaineering, you may well want to invest in a winter bag that is rated to twenty or thirty degrees below zero, in addition to a lighter bag for three-season use. Alternatively, some bags offer zip-out linings, so you have a double bag for cold weather, and your choice of the lining or outer bag for warmer conditions.
In general, three-season bags are rated to about 20 degrees above zero, which will work for warm conditions and usually be sufficient for brisk spring and fall nights. However, remember that there is no universal standard for bag rating. Also, people sleep at different temperatures, so while a 20-degree bag might keep your companion warm on a cold night, you might freeze in the same bag.
When you buy a bag, a good rule of thumb is to think about the coldest condition you might experience, and then drop down ten or twenty degrees. Keep in mind that it is more difficult to stay warm in an insufficiently insulated bag than it is to vent a bag designed for cooler temperatures. A bag rated to zero is usually a good choice, since it will keep you warm on unexpectedly cold nights, but can be zipped open for venting. When you buy a bag, any bag, there are several features you should check. Start at the top.
Hood. Most bags have a hood that can be drawn tight around your head in cold weather. Up to 50 percent of your body's heat can be lost through your head, so a good hood can greatly improve the efficiency of your bag. Get in the bag and pull the drawstring. Can you still breathe with the hood in place? Can you turn, or roll, without suffocating? A hood should have slightly more fill material than the rest of the bag, and when in place, still have room to accommodate a cap.
Draft collar. Scrutinize the draft collar, which is at the base of the hood. This insulated tube is designed to prevent heat loss from around your neck and shoulders. Rectangular, summer bags may not have draft collars, but they are an instrumental part of winter bags. The collar should be fluffy enough to fill the excess space between your neck and shoulders, but not so bulky you feel like you are wearing an inner tube around your neck.
Foot box. Since your feet take up room in the bottom of the bag, many sacks are designed with a flared, boxed, or barrel-shaped foot box to accommodate these protrusions better. In some mountaineering bags, extra room is added to the foot box to accommodate boots or water bottles.
Zipper and stitching. Look at the zipper and stitching. The zipper should have teeth big enough to run smoothly, without catching on fabric. Make sure the fabric has enough integrity to hold up along the sewn seams. Tug evenly at the seams to ensure that they don't separate from the fabric, and that the fabric stays in place. Stitching should be close and tight. Open the bag and look at the overall construction, features and finish of the bag to determine its quality.
Zipping bags together. One convenient trick is to zip two bags together to turn a single sleeper into a double. Many manufacturers use the same zippers. If bags have zippers that are similar in design, they can often be zipped together. If you are zipping two bags together, you can use bags of different warmths. In cold situations, put the thicker bag on top. Remember that mated bags provide less heat than separate bags, since there are more gaps and more movement to push out warm air. If you have a bag you might want to mate with your new purchase, bring it along to ensure compatibility.
Zipper flap. Most bags have an insulated tube or flap that runs parallel to the zipper in order to block heat loss. The tube should be sewn only to the lining material, since sewing through the bag creates holes that allow air leaks. Cold weather bags may have two thickly filled draft tubes. If there is a single flap or tube, it should be sewn to the top zipper so it hangs down when you sleep. Flaps or tubes that are too narrow may interfere with the zipper, so check out the action before you buy.
Pockets. Some bags come equipped with accessory pockets, but they can be more of a hindrance than a help. Are you a Princess and the Pea sleeper? Do you really want to roll over onto your glasses and car keys? If an accessory pocket sounds appealing, put items in it to test its position and padding.
Warranty. Ask about the bag's warranty. What is covered and for how long? Some companies offer a warranty on materials and workmanship for the owner's lifetime, others limit warranty to"faulty" materials and construction. If you buy a bag, note the name and customer service number of the manufacturer. Most companies will repair damaged equipment for a nominal cost.
Just like people, sleeping bags come in all sizes and shapes.
You want a sleeping bag that is big enough for comfort, but not so big that you are carrying unnecessary poundage in your pack. Dead space in a sleeping bag is difficult to keep warm. Extra room takes more calories to heat, so your body has a more difficult time keeping the bag warm. Also, insulation tends to get compressed if your bag is too tight around your body. Once it is packed down, it won't work efficiently.
It used to be that there was not much choice in bag length, but now they come in all increments. Select a bag that gives you several extra inches of length in both the bottom and top–so you can stretch–but no more.
A current debate rages over the need for women-specific bags. Some companies make the argument that bags should fit bodies, regardless of sex, while others contend that women's broader hips, narrower shoulders, and colder sleeping temperature necessitate differently cut bags.
Mummy bags, which are cut wider at the shoulders and narrower at the feet, are the most efficient (for both sexes), in terms of weight and warmth. Since the bag conforms more closely to the human shape, sort of like a sarcophagus, the space is warmed using minimal body heat. However, if you have a tendency toward claustrophobia, or like to wriggle around in your sleep, a mummy bag might be too restrictive.Rectangular bags have more room to toss and turn, but aren't as efficient for warmth. Because of the larger top opening, heat can escape more easily.
Semi-rectangular bags are a good compromise, with a tapered foot (roomier than a mummy) and contoured hood, and additional space at the torso for comfort. There is no universal consensus on the best fabric. Often bags will have a tightly woven synthetic shell with a DWR (Durable Water Repellent) finish. The higher the thread count of the fabric, the better the water and wind resistance. Check the entire bag for leaking fill, which is a sign that the fabric might not have a sufficiently tight weave.
Shells run the gamut from simple, smooth polyester/nylon taffeta to waterproof Gore-Tex. The majority of sleeping bags available have outer shells made from tightly woven polyester or nylon micro fiber that tends to be supple, light, and somewhat water and wind resistant. Ripstop is also another strong shell contender, mainly because the nylon/polyester is extremely durable. A smaller percentage of bags are made with Gore-Tex or Dry Loft shells. Gore-Tex is usually not recommended because it doesn't breathe sufficiently to allow moisture to escape to the outside of the bag. Dry Loft, also made by Gore, is more breathable and more highly water-resistant than most microfibers.
Down or synthetic, that is the question. For most first-time buyers, whether to invest in a fluffy goose down bag or a less expensive one filled with man-made fibers is a real dilemma. Insulative materials are sandwiched between the shell and lining fabrics using a variety of methods (enclosed channels, layers, baffles). Check on how the fill is distributed throughout the bag. Shake the bag, and make sure the fill stays in place. Insufficient baffles, channels or layers can allow the fill to migrate away from your body, compromising the integrity of the bag and its ability to keep you warm.
If you're car camping or relying on strong Sherpa shoulders, synthetic bags are a good choice. They do tend to be heavier and much bulkier than a down bag of comparable warmth, but they don't lose their loft over time, and require as much maintenance, such as airing out after each use to avoid dampness. Synthetic bags also retain much of their warmth, even after taking a soaking.
However, if you want to go light, with a small pack, down is your best choice. It's the Cadillac of bag fill, with a higher weight-to-warmth ratio than any synthetic fill on the market. But get down wet, and you're due for a cold night. Down also takes much longer to dry than synthetic fiber.
Synthetic fills come in many forms and a bewildering variety of brand names. The technology behind them keeps getting better and better, yielding fibers much closer in weight, warmth, and compressibility to down than ever before. For the best performance, look for sleeping bags stuffed with Lite Loft, Polarguard 3D, Thermolite Extreme, and PrimaLoft Sport (formerly PrimaLoft 2).
Fiber manufacturers vary certain fiber characteristics to improve the thermal performance of a batting (increase its insulation per unit weight). They can vary the fiber diameter (denier), fiber length (from short staple lengths to long, continuous filaments), the shape of the fiber cross section, fiber crimp, and the size and shape of holes or voids inside the fiber. Batting producers can vary the thickness, density, and weight of the fiberfill also. Down bags will each have a fill power number. The number indicates how much space an ounce of down can fill. The higher the fill power, the loftier and warmer the bag.
Wet bags. Wet bags aren't as warm as dry bags. A simple means of keeping your sleeping bag dry is to place it inside a plastic garbage bag. (You can then use the bag for garbage on your hike out). If you have a down bag, always allow the bag to dry before you place it in your stuff sack. If possible, hang any bag outside of your tent in the morning, until you are sure the moisture has wicked away. The caveat here is to avoid excessive sunlight, so either find a shady place or pack up your bag before the day gets hot. Most shell fabrics are treated with a DWR (durable water repellency coating). Check the bag's care manual for when to reapply a waterproof booster.
Eating and drinking also affect sleeping. Remember to eat and drink before going to bed. The warmer the food, the warmer you'll start out. If you go to bed cold, it is more difficult to warm up your bag. A brisk walk before bed, or a few stretches in the tent, can help to boost your body temperature. If you find you get cold sleeping at home, you'll probably have the same difficulties on the trail, so invest in a warm bag.
Tent or bivy sack. A tent or bivy sack will add at least 10 degrees F to the warmth of your bag. You can also invest in an outer bag or bag liner to boost your bag's capabilities for those frigid occasions.
Sleeping pad. Always use a sleeping pad. It will help prevent conductive heat loss between you and the ground, as well as providing a more comfortable berth.
Extra clothing. Bring along a light hat, gloves, and a pair of warm socks, even for summer camping. They can add crucial warmth on cold nights. Sleeping nude is not warmer than wearing a layer of clothing, but don't sleep in the clothes you wore hiking during the day, since they may be wet with sweat. Bring along a layer of warm, comfortable clothes to wear inside your bag, but none so bulky that they restrict circulation.
Tent placement. Consider the placement of your tent or sleeping pad. Low areas may become pockets for cold air. High elevations, especially when exposed to wind, can also present a chilly problem. If possible, select a sleeping spot that is protected from the wind and weather.
Bag handling. Shake and fluff your bag several times before jumping in. This is especially important for down bags, which may need time to fully loft. Some manufacturers recommend placing your bag (synthetic or down) in a warm dryer before embarking on a camping trip. The tumbling will help to fluff the bag, and will rid it of any residual moisture.
Stuffing your bag decreases the life of the loft. Don't store your bag in a stuff sack, rather hang it in a cool dry place. When you do stuff your bag for travel, do it gently, and avoid leaving the stuffed bag in a hot car.
Care instructions. Don't toss the manufacturer's care instructions. Always read and follow them. Since fabrics and insulation differ, they might require different care. Most bags can be washed with a mild detergent (you can buy down-specific cleaning agents) in your bathtub or an industrial washing machine. Don't get your bag dry-cleaned.