Bags for use in below-freezing temperatures should have large hoods in which you can bury everything but your nose. Bags for warmer conditions sometimes have smaller hoods, or even no hood at all, to save weight. In above-freezing temperatures, I often find the hood too warm and fold it under the bag.
Draft Collars
A filled, drawcord-adjusted collar or neck baffle to prevent drafts is a feature of many bags, especially those designed for cold weather. It lets you close the bag around your shoulders while leaving the hood open. The most basic, lightest bags don’t have draft collars. You can drape a shirt or warm top around your shoulders if necessary. Baffles usually have a drawcord adjustment and snap fastenings on the zipper side. I find them restrictive, so I do them up only when it’s really cold. Some makers—GoLite, Marmot, Western Mountaineering—have a smaller filled tube in some of their bags that seals around the face rather than a large collar. This saves a bit of weight, since it requires less material than a draft collar.
Boxed Feet
To keep your feet warm, a sleeping bag should have a shaped or boxed foot section. If the two halves of the bag are simply sewn together at the foot, your feet will compress the fill when they push on it, reducing loft there. A boxed foot has an extra circular section, which could be made either in channels or as a single unit. Cold-weather bags may have an offset double layer of fill in the boxed foot. In down bags, some boxed feet have internal box walls.
Zippers
Almost all bags, except for the lightest down ones, now have zippers, usually on the side, occasionally on the top. For years I distrusted zippers—they added weight, leaked heat, and had the potential for disaster if they broke. I’ve now developed a grudging acceptance of them, since the latest ones are pretty tough, though I still can see no real advantages. In theory, zippers allow you to regulate temperature and make getting in and out easier. Some bags can be zipped together to make a double bag.
Most bags have full-length side coil zippers. A few curve up toward the top of the bag at the hood to make using them easier. Some bags have short central zippers, a style that used to be standard. To prevent heat loss, zippers usually have filled baffles on the inside, though these may be absent in bags for above-freezing temperatures. Unfortunately, baffles snag zippers. A stiffened, antisnag strip will lessen the number of times the zipper catches, though these are far from perfect. When the zipper does jam, as it will, don’t try to yank it free—you could tear the fabric and damage the zipper. Gently ease the fabric sideways out of the zipper teeth. Two-way zippers let you open the bottom of the bag so you can stick your feet out to cool off if you overheat. You could even waddle around outside wearing your bag as a somewhat restrictive, but very warm, coat. Some sleeping bags are designed for this purpose and come with sleeves (the down-filled Nunatak Raku Alpine, weighing 32 ounces) or zipper openings for the arms (Feathered Friends down-filled Rock Wren at 27 ounces, Exped down-filled Wallcreeper at 33 ounces).
Warmth
Rating sleeping bags for warmth is difficult. There’s no standard rating system, and even if there were, individuals aren’t standard and feel the cold differently. Most companies use temperature ratings. These give the lowest temperature at which the bag should keep you warm. Thus a bag may be described as a 40°F (5°C) bag or a 20°F (−7°C) bag. Another figure sometimes given is the bag’s loft. What’s important is the loft over the body, not the total thickness of the bag. Makers usually give the total loft, though some also give the loft for the top half of the bag. Halve the first to see how much loft you’ll have around you.
Although there’s no standard, bags with comparable weights of the same type of fill should keep sleepers comfortable over roughly the same temperature range. I’d be very suspicious of any maker that rates a bag as vastly warmer than competitors’ bags with a similar weight of the same quality of fill.
No rating system, however, can account for the different metabolic rates of different bodies. Warm sleepers, like me, can use lightweight bags below their rated temperatures; cold sleepers may shiver a summer night away in a bag made for polar conditions. I have a friend who sleeps buried in a four-season mummy bag while I’m comfortable in a summer bag with the hood open. Be realistic about how warm you sleep. It’s easy to be tempted by a too-light bag in order to save weight. (A friend pointed out that it’s just as easy to be tempted the other way and buy too heavy a bag to be sure of sleeping warm.)
Having tested dozens of sleeping bags over the years, I conclude that ratings for down bags are pretty accurate for a warm sleeper like me, while synthetic bag ratings are usually on the optimistic side. I recently tested fifteen bags for a magazine review—eight synthetic, six down, and one a combination down-synthetic. I was chilly in all the synthetic bags at temperatures higher than their ratings but warm at the rated temperature in five of the down bags, the only exception being a bag with no fill on the bottom. The combination bag was also warm at the rated lowest temperature. I measured the loft of each bag. None of the synthetic bags had as much loft as the lowest-lofting down bag; mostly they had half the loft of down bags with the same temperature ratings. Adding five or ten degrees to the rating of a down bag and more to a synthetic one would be wise for many people.
Other factors also influence how warm you’ll sleep. Food is fuel is heat, so however tired I am at the end of a long day, I always try to eat something before going to sleep on a cold night; if I don’t, I wake up in the early hours of the morning feeling chilly. (If it’s warm and I don’t eat, I wake up because I’m hungry!) Putting on some clothes is an obvious thing to do when you wake up in the night feeling chilly, but a carbohydrate snack can also help warm you up. If you don’t eat, fatigue can keep you shivering long after you expect to be warm. The weather is a factor, too—high humidity means a damp bag (though it may feel perfectly dry), less loft, and conductive heat loss. Thus you may feel colder when the temperature’s near freezing and the humidity is high than you do when it’s below freezing but dry. Wind reduces a bag’s efficiency, as does sleeping under an open sky with no barrier to prevent radiant heat loss. If you regularly sleep under the stars, you’ll need a warmer bag than if you always use a tent. Any barrier can make a difference. I’ve sometimes slept under a tree with the foot of my sleeping bag outside the tree’s cover and awakened to find the foot of the bag covered with frost.
In cold weather, sit in your sleeping bag to keep warm.
Weight
High loft requires more fill, which means more weight. Down-filled bags are much lighter than synthetics across all temperature ranges, from about 1 pound for 40°F (5°C) bags to 2.5 to 3.5 pounds for 0°F (−18°C) models. The lightest synthetic-fill bags start at about 1 pound, 12 ounces for a 40°F bag and 3.5 pounds for a 0°F bag. Based on weight alone, I’d choose a down bag, especially since my experience suggests that synthetic bag ratings are on the optimistic side.
Models and Choices
There are hundreds of sleeping bags—371 from thirty-four companies in Backpacker’s 2004 Gear Guide. However, it’s fairly easy to reduce the choice to a handful of models that fit your specific criteria. I look for the lightest, least bulky bag—which means one with down fill—that will keep me warm when I sleep unclothed in a tent in the average temperatures for the time and place of my trip. If temperatures are cooler than average, I wear clothes in the bag.
Several years ago the lightest 40°F (5°C) bags weighed about 25 ounces and had 10 ounces of down fill. New lighter shell fabrics and higher-lofting down mean they now weigh 16 ounces and have 8 ounces of down fill. I have two of these ultralight bags, both of them favorites. The first is a British-made 32°F (0°C) Rab Quantum 200, with 7 ounces of 850+ fill-power down, box-wall construction, a hood, and a Pertex Quantum shell. The weight is 16 ounces. There’s no zipper. I took it on a five-week hike in the High Sierra and needed to wear clothes in it only on the five nights when the temperature dropped below freezing. My only complaint is that the lining is white an
d shows dirt. My other ultralight bag is a 40°F Western Mountaineering HighLite, which also has a Quantum shell and weighs 16 ounces. It has 8 ounces of 850+ fill-power down contained in chambers that are square rather than long and thin and that have sewn-through horizontal seams and baffled vertical seams. There’s a half-length zipper and a hood, and the lining is black. Both bags are fine for summer trips when I’m expecting temperatures to be mostly above freezing, and they can be used together, since the Quantum 200 is cut slightly smaller than the HighLite. Similar bags weighing under a pound and a half are sold by Exped, PHD, GoLite, Marmot, Mountain Hardwear, Mountain-smith, Nunatak, Sierra Designs, and Bozeman Mountain Works.
These ultralight summer bags are fine for warm sleepers like me, but many people will find them inadequate in all but the very warmest temperatures (over 45°F [7°C]). Bags in the 15 to 25°F (−9 to −4°C) range are the standard for three-season use. The weights of these have come down as well, with many below 2 pounds, though some weigh as much as 3.5 pounds. The ones at the lighter end (with 16 to 20 ounces of fill) should be adequate for most people. Of the ones I’ve tried, I like the 1-pound, 11-ounce, 20°F (−7°C) GoLite Feather, which has 18 ounces of 800-fill-power down (700-fill-power in my early model) and a Pertex Quantum shell. There’s a quarter-length zipper on the top and an excellent-fitting hood. The Feather has kept me very warm at 28°F (−2°C), and it’s now my first choice for trips where temperatures are likely to be between 20 and 32°F (−7 to 0°C), which generally means spring and fall. Most makers have bags like this—it’s the closest thing you can find to a general-purpose bag.
My well-used winter bag sees little use these days because I rarely venture into areas where the temperature will be below 15°F (−9°C) on many nights, for which the Feather plus clothes is adequate. In colder temperatures the HighLite and Feather bags combined only weigh 2 pounds, 11 ounces and are warmer, smaller-packing, and more versatile than the winter bag. My bag (the model hasn’t been sold for many years) is typical of many winter bags: it weighs 3.5 pounds, with 26.5 ounces of 650-fill-power down. It’s rated to 0°F (−18°C) and is warm at 5°F (−15°C) but too hot at 35°F (2°C). Most makers offer similar bags, as well as bags designed for much colder temperatures. If I were replacing my old bag it would probably be with a Marmot Lithium. I borrowed one of these 0°F-rated bags for a spring ski trip and was extremely impressed. It contains 27 ounces of 900-fill-power down, has a Pertex Quantum shell, and weighs 2.5 pounds, less than many 20°F (−7°C) bags. There’s a half-zipper and a superbly comfortable hood. Marmot’s two other bags in this 900-fill-power series, the 15°F (−9°C), 29-ounce Helium and the 30°F (−1°C), 21-ounce Hydrogen look excellent too.
Combining bags is a good way to increase the warmth while keeping the versatility of two bags. Not all combinations are comfortable, however, and some can be hard to get in and out of, so it’s best to check that bags are compatible before trying them in camp. Obviously the outer bag will need to be roomier than the inner one. Some makers offer bags designed to fit inside others, such as Western Mountaineering’s 45°F (7°C), 14-ounce LineLite, which has no hood or boxed foot so it will fit easily inside other bags.
I use synthetic bags only when they’re sent to me for tests and reviews, but they’re the ones most people buy. I find down softer and more comfortable, as well as lighter and more packable. If I were buying a synthetic bag, I’d look for Polarguard or Primaloft, and I’d choose one rated 5 to 10° lower than the temperatures I expected to use it in. I did try a 54-ounce, 20°F (−7°C)-rated Polarguard 3D bag on a nine-day trip and found it warm and quite comfortable, though the coldest overnight temperature was only 36°F (2°C). A down bag half the weight would have been just as warm and much smaller-packing.
Carrying
Sleeping bags are best carried inside the pack, where they are protected from rain, dirt, and damage. I pack my down bag at the bottom of the lower compartment, in an oversized waterproof stuff sack (see page 122). The oversized stuff sack lets the bag mold to the curve of the pack around my lower back and hips and fill the corners. A round stuff sack packed to bursting is very hard to fit in a pack without leaving lots of unfilled space. If I use a synthetic sleeping bag I pack it in an even bigger stuff sack and carry it packed as loosely as possible at the top of the pack, since compression reduces the loft of a synthetic bag. Because they are bulky when packed, many synthetic bags come with compression stuff sacks. These should never be used unless you like replacing your sleeping bag frequently.
Care
In the field, all sleeping bags benefit from being aired whenever possible to let any moisture evaporate. This is especially important with down bags, which can absorb a surprising amount of moisture overnight. It’s also a good idea to remove down bags from their stuff sacks a while before you use them to let the fill expand, and to give them a shake before you climb in, which helps distribute the fill. Neither makes the slightest difference to synthetic bags.
Patch small cuts or holes in the fabric with rip-stop nylon tape or duct tape to prevent fill from escaping. You can sew a patch on when you return home—just remember to coat the stitch lines with seam seal to make them downproof. If tendrils of down start to work their way through the fabric, don’t pull them out, which may enlarge the hole. Instead, pull the down cluster back into the chamber from the other side.
At home, always make sure a bag is dry before storing it and never store a bag compressed; prolonged compression may damage the fill’s ability to recover so it won’t loft fully anymore, reducing the warmth. This affects synthetic bags the most; prolonged compression can destroy virtually all the loft. Bags should be stored so that the fill can loft—either flat, hung up, or packed loosely in a large bag. They need airflow round them, too, so don’t store them in a waterproof bag; cotton, polyester-cotton, or mesh is ideal. Many manufacturers provide breathable storage sacks with sleeping bags.
Whatever the outer fabric, the shell should have a durable water-repellent (DWR) treatment. As with clothing, this treatment will wear off in time; it can be restored by low-heat tumble-drying, which also helps break up any clumps the down may have formed. Running a warm hair dryer over the bag could help revive the DWR, too. Ironing should work, but I wouldn’t risk ironing a sleeping bag. When the DWR has gone completely, which does happen, you can apply a spray-on DWR treatment (see pages 176–78). Wash-in water-proofing also can be used, though drying the bag thoroughly—which is essential—is said to take a very long time.
Airing a sleeping bag on top of a tent. GoLite Feather.
Airing sleeping bags on skis at a spring camp.
Eventually a well-used bag will need washing. With down bags this requires great care. Down loses some of its insulating properties every time it gets cleaned, so you should do it only when the fill is so dirty that it no longer keeps you as warm as it should. If only the shell is dirty, it can be sponged clean. Synthetic fills may be damaged by washing too, so again do so only when absolutely necessary.
When washing a bag take great care. Down absorbs vast amounts of water, and a wet bag is very heavy; if it’s lifted when wet, the baffles may tear under the weight of the wet down, so sliding it into a laundry basket is a good idea. Most instructions say bags should be hand washed in a large tub or else washed in a front-loading machine and dried on low heat in a large commercial tumble dryer to keep the down from forming clumps. You need a special down soap such as Nikwax Loft Down Wash, since detergents strip the natural oils from down and shorten its life. I always send down bags out to be washed by professionals. This relieves me of the task and increases the likelihood that my bag will survive. Many experts think that improper cleaning ruins more down bags than anything else, including prolonged use.
If you decide to have someone else wash your bag, ask for recommendations from the store where you bought it or from the manufacturer. Dry cleaning isn’t recommended for sleeping bags, since the solvents can remove the down’s natural oils. The fumes fr
om dry-cleaning chemicals are poisonous, too, so any bag that is dry cleaned must be aired well before being used.
Reconstruction
The shell of your down-filled bag eventually may become dirty enough that no cleaning company will touch it. This happened with the bag I used on the Continental Divide walk. It had a polyester-cotton inner shell, which was in appalling condition after 157 nights’ use. Cleaners I approached wouldn’t handle it, saying the inner shell was rotten and would disintegrate during cleaning. Since the expensive goose-down fill still lofted well and kept me warm, I was loath to throw the bag away, so I had it remade. This cost less than half the price of a new bag and included washing the down. The resulting bag not only was a better fit, since I could specify the length, but it weighed just 2 pounds rather than 2 pounds, 12 ounces because the new inner shell was nylon.
Liners
One way to improve the warmth of a sleeping bag is to wear clothes in it. This keeps the bag clean and extends its life too, because it needs washing less often. A liner accomplishes the same thing but adds weight. Clothes you can wear at other times; liners aren’t much use for anything else. I don’t really like liners because it’s easy to get tangled up in them. Liners come in cotton, wicking synthetics like CoolMax, silk, fleece, and coated nylon. I’d disregard cotton entirely because of its weight, absorbency, and slow drying time. Synthetic liners make more sense—Cocoon’s CoolMax Mummy Liner weighs 9 ounces. Silk is really light and low in bulk, and I have a 4.5-ounce Cocoon mummy-shaped silk liner that I sometimes use when weight isn’t important. It’s what I’d recommend if you really want a liner.
Chris Townsend Page 34