After an hour of stumbling through the dark cirque, with spindrift gusts stinging my eyes and plastering my clothing with wet ice crystals, I finally discovered a boulder that served as a wind break. I tucked behind the boulder, crawled into the Brooks Range Drift 15 sleeping bag, cinched the draw-cord tight and hoped that the hydrophobic-treated down insulation would keep me warm.
As many people know, down insulation offers an unsurpassed warmth-to-weight ratio, and it excels in dry conditions. But, it is all but useless when wet. This makes down bags a hard fit for climbing or backpacking in wet climates like the Pacific Northwest.
The insulation in the Brooks Range Drift 15 sleeping bag is treated with DownTek, a down coating that prevents the feathers from absorbing water. Since water rolls off the down, the feathers stay light and fluffy—keeping you warm. Unlike synthetic sleeping bags, which are typically bulkier and heavier than down, treated down sleeping bags offer the lightweight, low bulk warmth found in down bags without sacrificing packability.
The Drift 15 is designed to be used comfortably from 20 degrees F down to -7 degrees F. This sleeping bag is roomier in the chest than comparable ones from Feathered Friends and Western Mountaineering and the extra two inches of girth in the shoulders and hips allows ample room for keeping gear warm. Plus, if it gets really cold, I have room to layer up without feeling squished. According to Brooks Range, this sleeping bag's shoulder width is 62" and the hip width is 58" in regular. The long bags are one inch wider in the shoulders and hips and two inches longer.
I like the compressibility of the Drift 15; it easily stuffs into a 7 inch by 12.5-inch stuff sack, which is slightly smaller than comparable sleeping bags by Feathered Friends and Western Mountaineering. Brooks Range designed the Drift 15 with 20.5 ounces of 850 fill-power down and a lightweight 15-denier rip-stop nylon shell. The nylon's relatively low thread count keeps the bag's weight and bulk down without sacrificing too much durability. For example, I scraped my ice axe on the sleeping bag and it didn't leave a mark.
Treated down weighs more than untreated down. This means the DownTek coating adds a bit of overall weight, so the Drift 15 (size medium) weighs 2 pounds (32 ounces), about average for a 10 or 15 degree sleeping bag.
I slept well that night behind the boulder thanks to the cinched hood that kept air from creeping in and robbing me of warmth. During the night snow collected on the bag and melted near my face and over my chest, In the morning, the surface of the bag was soggy despite the durable-water-repellent (DWR) coating, but the down remained lofty and I couldn't feel any wet clumps. And, the small internal pocket above the chest was close enough to my ear for me to hear my watch alarm for an alpine start.
For additional testing, I exposed the Drift 15 bag to an April sleet storm for six hours alongside an old, conventional down bag and a Feathered Friends bag made with Pertex Endurance (a waterproof-breathable membrane fabric). After this heavy precipitation, the old bag was soaked. The Drift 15 was wet with some water beading on the fabric, and the Feathered Friends bag was covered in beaded droplets of water. Inside, the Drift 15 felt wet, although it retained most of its loft, and when I shook it off and crawled inside the bag felt damp, but sleep-able. In another test, I fully submerged all three bags for a minute in the tub. The Drift 15 bag fluffed back to life after a couple minutes of vigorous shaking, while the other bags did not. Then I climbed inside the Drift 15 and noticed it still had enough loft to provide some warmth.
While the Drift 15 is expensive, the price is comparable to other bags in the same category.