Feathery cocoons
Zipping into the finest lightweight down sleeping bags

A few years back, my friend Pete and I topped out on Andromeda Strain, a huge mixed alpine route in the Canadian Rockies. We were cold, tired, and unsure about how to get off the mountain. After wandering around by headlamp in the inky night for a few minutes, it soon became obvious that our safest option was to wait until dawn before heading down. No big deal, except that we had left our bivy gear at camp, hoping to sprint the route in a day.

We crawled into our packs, sat down on the ropes, and resigned ourselves to the fact that for the next 10 hours we were going to be absolutely freezing. Carrying bags would have slowed us down a bit, but with two feet of fresh snow on the route, we should have expected to be benighted. Immediately after that endless night of shivering five years ago,

I ponied up for a two-pound down bag, and have since been toasty warm on even the crummiest of forced bivies. Since coughing up the cash for my purchase, however, advancements in lighter shell material, smaller zippers, and loftier fill have vastly improved the warmth-to-weight ratio of the current crop of lightweight down bags, mandating that I start shopping for an upgrade.

First, I trimmed the crowded field down to encompass only the bags that met my climbing-specific needs. I wanted a down bag with a 15- to 20-degree Fahrenheit temperature range, weighing 2 pounds, 5 ounces or less, and offering a full- or three-quarter-length zipper.

This review excludes bags with synthetic insulation because down is warmer and more compressible for its weight than man-made fibers — crucial considerations for any alpinist. Down is also incredibly durable. Synthetic bags start to show degradation after just a few seasons of heavy use. Treat a down bag well, though, and it will last you 15 years. Plus, feather bags have a natural comfort range thanks to hairs on the down clusters that react to the outside temperature. When it’s cold, the hairs stiffen and loft increases. In warmer temps, the hairs relax. And let’s not forget about comfort! Nothing feels better than zipping yourself into a heap of feathers after a long day out. The only drawback to down is that it’s useless when wet (Synthetic fill retains some insulative value when wet, making it suitable for soggy environments). However, with today’s new shell materials you’d be hard pressed to thoroughly soak your bag unless something drastic happened — like an open bivy in the rain.

All of the bags tested use an advanced polyester or nylon shell that has been coated with a durable-water-repellent (DWR) treatment. A few of the bags opt for microfiber shells for their increased water and wind resistance, a result of packing the threads of the fabric so close together that the elements can’t sneak through. Feathered Friends goes one step further, using a relatively new fabric called Epic. Epic is unique because a permanent, water-resistant, silicone-based polymer encapsulates each fiber of the fabric, guaranteeing outstanding water and wind resistance for the life of the bag.

What about waterproof/breathable shell fabrics? They offer only a slightly higher degree of water protection than today’s new high-tech shells, cost significantly more, and are not nearly as breathable, tending to trap sweat in the down.

A great way to compare one bag’s potential warmth to another is via its fill weight, i.e. how much down is in the bag. Consider the size of the sacks you are comparing along with the quality of the down used. A bigger bag with the same fill weight as a smaller bag will not be as warm, just as a bag with considerably higher quality and lighter down may be warmer than a bag with heavier, low-quality down. So, as a general rule when choosing between similar-sized bags, the model with the highest fill weight should be the warmest.

Full-length zippers help to increase a bag’s versatility — if it’s unseasonably warm, you can turn your bag into a blanket, and when you feel claustrophobic, it’s easy to stick a foot out. Three-quarter-length zippers are an ounce or two lighter (ideal for the weight conscious) but tend to limit comfort, and can prevent you from zipping your bag into a mate’s.

Another key characteristic is open baffles. This lets you move the fill from the bottom of the bag to the top when you need more insulation, and vice-versa, thereby increasing the temperature range of the bag.

After crunching the numbers, a crew of testers and myself headed into the backcountry to see if the zippers ran smoothly or snagged, and if the hood was easy to use, especially in the middle of the night when the pee demon woke us with full bladders. We also checked to see if the bags had insulated neck collars. For some testers, this handy feature helped reduce heat loss from the top of the bag when the hood was partially open.

We did not attempt to answer the slippery question, “Which bag is the warmest?” An almost infinite number of variables would have to be accounted for in order to accurately judge the warmth of the six bags in this review. Eat a triple helping of pasta before hitting the rack and you might sweat all night long. Conversely, bedding down tired, hungry, and dehydrated will probably set you up for a cold night no matter what the bag’s rating. Instead, we tried to establish whether or not the manufacturer had rated the bag accurately. To the manufacturers’ credit, all the bags tested fell within their official temperature range.

Finally, I busted out the digital scale and weighed the stuff sacks. Most companies sell their sleeping bags with a standard mid-weight nylon sack, while a few others include an ultra-light rig. REI goes one step further and throws in a compression sack. It’s interesting to note that an ultra-light stuff sack saves one ounce over mid-weight sacks, and two ounces over a compression sack. The weights listed below are for the sleeping bags sans sacks.