The aptly named The North Face Inferno -20 is one of the warmest bags in its class. It achieves this with a combination high loft down and a conservative(ish) cut, leaving less uninsulated space than the wider Marmot Col -20. A unique, half-length two-way zipper zips in the warmth from the top the bag and dissects a series of trapezoidal baffles. While the winds howled outside, our testers found themselves pleasantly roasting inside this high lofted heat-trapping sack. However, when warmer spring temperatures arrived, our testers were burning up and wished they could fully vent the bag.
The North Face Inferno -20 Review
Compare prices at 3 resellers Pros: Super warm, thermally efficient
Cons: Half length zipper doesn't allow for venting the footbox
Manufacturer: The North Face
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Our Analysis and Test Results
This bag is one for the minimalists who find themselves sleeping out in the lowest of low temps. It's warmer than the Big Agnes Crosho -20 and more heat-efficient than the Marmot Col, but not as versatile as either of those bags. Because of the half zipper and the lack of any venting for the lower body, the Inferno -20 is only appropriate for the coldest of winter climates. What it does have going for it is an impressive warmth-to-weight ratio.
The Inferno cranks up the heat with 36.4oz of 800 fill down. That's more down than the Feathered Friends Snowbunting, the Western Mountaineering Kodiak MF. Only the hefty Marmot Col -20 has more down. The zipper is offset with the baffles on the top of the bag, so there is not a dedicated draft tube protecting the zipper. Instead, an extension of the chest baffles sits between the user and the elements. Arguably, this may work better than a closed draft tube, since it allows warm air to circulate into the zipper area. Our testers, human and ignorant to the subtle movements of hot air, didn't pick up on any cold spots near the zipper, so we feel confident in saying that this design performs as well as a regular draft tube. The draft collar contains an ample amount of snuggly down and tightens in conjunction with the dual hood cinches.
Tipping the scales at 3 lbs 7 oz, the Inferno scores toward the bottom of the competition in the weight metric. The shell fabrics make up a large percentage of the Inferno's total weight. This is hardly noticeable to the user, but considering that the Kodiak has a full-length zipper and a roomier cut and is still lighter, and the advantage of lighter materials becomes apparent. While this bag doesn't have as good of a warmth-to-weight ratio as the Kodiak, it's still much warmer than heavier bags like the Kelty Cosmic Down 0, The Big Agnes Storm King 0, and the slightly lighter Rab Ascent 900. If you need less warmth and a cheaper price point, these contenders might be for you.
An inch wide strip of fleecy material lines the draft collar where it touches the chin, giving a general impression of plush snugglyness. Our testers who primarily sleep on their backs felt the cut of the bag is plenty wide, but the side sleepers among us preferred the more generous cut of the Marmot Col -20. The two-way half-length zipper makes it difficult to vent the footbox sufficiently, and on a warmer night where temperatures climbed into the high 20s, one of our testers (a self-proclaimed cold sleeper) felt so hot that she had to completely get out of the bag and cool off. The Inferno earned a fair score for comfort, whereas the Nemo Sonic 0 and Western Mountaineering Kodiak MF were top scorers.
The Inferno -20 packs down smaller than the Marmot Col, but a touch larger than the Western Mountaineering Kodiak MF, since it has a heavier shell fabric and just a little bit more down. The Inferno's high fill goose down makes it much more compressible than the Kelty Cosmic Down 0, though it's almost triple the price. It's one of the few bags that comes with a stuff sack that has compression straps, which we appreciate.
The most apparent and unique feature on the Inferno -20 is the half-length, two-way zipper located on the top of the bag. This design saves a little weight, and the two-way zipper allowed our testers open up a hole in the front of the bag to stick their hands through so they were able to drink coffee and eat breakfast while remaining almost completely inside the warm bag!
Again, the disadvantage of the half zipper is that you can't vent the foot box as well as a full-length zipper. The hood has a cinch cord on either side the like a jacket, but it doesn't really tighten the draft collar. Finally, a small zippered stash pocket is located inside the bag over the left side of the chest. Top scorers in this metric include the Big Agnes Storm King 0 and the Marmot Col.
The silky feeling Neovent Air shell fabric does an excellent job of protecting the down from moisture, but not quite as well as the Marmot Col or the Feathered Friends Snowbunting, earning the Inferno a strong score in this metric. The shell proved itself to be truly waterproof and breathable in our submersion test: we squeezed out all the air and no water was able to penetrate the fabric and a barely detectable amount of water entered through the seams. We realize this test is beyond what these bags were designed to handle, and feel the Inferno can easily deal with the frozen forms of precip it will encounter in its natural habitat.
We recommend this bag exclusively for colder temperatures since it's not very versatile due to the half zipper. However, it keeps out the cold and beats back the weather while remaining light and packable enough to carry into the mountains.
At $599, the Inferno -20 is a big investment. It doesn't have as good of a warmth-to-weight ratio as the Big Agnes Crosho -20, a similarly priced bag that also features a half zipper design.
The North Face Inferno -20 is an excellent bag that warmed us up and kept us cooking through the night. If you're interested in its unique design, but want less or even more(!) heat, it is also available in -40, 0, and 15-degree versions. If this warm of a bag is not a necessity, consider the Nemo Sonic 0, Western Mountaineering Versalite 10, Western Mountaineering Antelope MF, Rab Ascent 900, Big Agnes Storm King 0, and the Kelty Cosmic Down 0. While these bags may earn a lower overall score, they are a pretty penny cheaper.
— Matt Bento