The world's most in-depth and scientific reviews of gear

Best Winter Down Sleeping Bags of 2021

Our seasoned testers took these bags on winter adventures, like backco...
Photo: Matt Bento
Thursday December 24, 2020
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Meeting the cold head-on for 2021, our experts have tested 27 of the best winter down sleeping bags over 8 years. Purchasing 13 of the best and warmest, we spent months of winter camping while sacrificing the comforts of a warm house. Tried and tested by ski patrollers, road trippers, and climbing dirtbags in the mountains through the cold months in California's High Sierra, we've got a pretty good handle on which bag is warm and which don't stack up. We meticulously evaluate key performance metrics to score each product. Our comprehensive review offers recommendations based on proven performance for those seeking to save a buck and for those seeking the best bags of feathers on the market.

Top 13 Product Ratings

Displaying 6 - 10 of 13
 
Awards Top Pick Award     
Price $717.75 at Amazon
Compare at 3 sellers
$625.00 at Amazon$500 List$299.95 at Backcountry$398.00 at Amazon
Compare at 3 sellers
Overall Score Sort Icon
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Pros Very warm, most weather resistant in its categoryWarm, incredibly lightGood warm-to-weight ratio, very compressiblePlenty warm, comfortable hood, bomber outer fabricWarm, comfortable hood, ultra light shell fabric
Cons Heavy, zipper snagsWeak neck baffle Velcro, shallow hoodNot as warm or as comfortable as the KodiakLow end down, substantially heavier than many other bagsNeck baffle integrated with zippe baffle (not a true neck baffle), low weather resistance
Bottom Line This is an excellent bag for hunkering down and waiting out bad weatherThis lofty, lightweight bag has an excellent warmth-to-weight ratioThis bag offers decent warmth and weight for $100 less than the top performersAlthough not our top budget pick, this bag delivers when you need warmthIf you sleep in a tent and take to keep your bag dry, this is the one for you
Rating Categories Marmot Col -20 Antelope MF Rab Neutrino 800 Mountain Hardwear Rook 0 Marmot Lithium
Warmth (20%)
9
6
7
7
7
Weight (20%)
3
8
7
5
7
Comfort (20%)
7
6
7
7
5
Packed Size (15%)
5
7
7
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7
Features (10%)
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6
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6
Weather Resistance (15%)
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Specs Marmot Col -20 Antelope MF Rab Neutrino 800 Mountain Hardwear... Marmot Lithium
Measured Weight (lbs, size Regular) 4.08 lbs 2.63 lbs 2.85 lbs 3.20 lbs 2.90 lbs
Fill Weight (oz) 44 oz 26 oz 28 oz 33.2 oz 27.8 oz
Type of Down Fill Goose Down Goose Down European Goose Down Down RDS Cert/Fluorine Free Goose Down
Fill Power 800 850 800 650 800+
Material Weight (excludes down, oz) 21.3 oz 16 oz 17.65 oz 18 oz 14.12 oz
Temperature Rating -20° F 5° F -4°F 0°F 0°F
Pocket Yes No Yes Yes Yes
Shoulder Girth (inches) 64" 62" 59" 60" 61"
Hip Girth (inches) 61" 53" 51" 55" 56"
Foot Girth (inches) 47" 39" 49" Not listed 42"
Shell Material Pertex Microlite 30 Denier 20 Denier Microlite XP Pertex Quantum 30D nylon, DWR treatment Pertex 20d 100% nylon ripstop
Continuous Baffle Yes Yes Yes No No

Best Overall Cold Weather Down Sleeping Bag


Western Mountaineering Kodiak MF


Western Mountaineering Kodiak MF
Editors' Choice Award

$710.00
at Backcountry
See It

74
OVERALL
SCORE
  • Warmth - 20% 8
  • Weight - 20% 7
  • Comfort - 20% 8
  • Packed Size - 15% 7
  • Features - 10% 7
  • Weather Resistance - 15% 7
Weight: 2.85 lbs | Fill: 30 oz of 850-fill goose down
Super roomy
Stellar warmth-to-weight ratio
Snag-free zipper
The price

The Western Mountaineering Kodiak MF is our favorite cold weather bag. WM has been quietly churning out this bag to a devoted following of adventurers for years. Like the Antelope and the Versalite, this bag has a huge 3D draft tube and a snag-free zipper. What elevates its score is the super comfy 66" cut in shoulders and its 30 ounces of 850 fill down, making our favorite balance of warmth, weight, and comfort for winter camping in the lower 48. Testers loved that they could sleep on their stomach, side, or back without skipping a beat AND hold all of the gear that needs to be insulated, all while staying comfortable. It also packs down small.

Extra room in a sleeping bag is nice if you're going to be spending weeks at a time under the stars, but keep in mind that uninsulated space won't feel as warm as a tighter fitting bag. You can remedy this by stuffing your extra layers and jackets in the bag with you. Western Mountaineering bags are the gold standard, but they're expensive. Care for it, though, and this high-quality model could last decades of winters.

Read review Western Mountaineering Kodiak MF

Best for Fast and Light Winter Camping


Mountain Hardwear Phantom 0


73
OVERALL
SCORE
  • Warmth - 20% 8
  • Weight - 20% 8
  • Comfort - 20% 8
  • Packed Size - 15% 5
  • Features - 10% 8
  • Weather Resistance - 15% 6
Weight: 2.68 lbs | Fill: 29.6 oz of 850-fill goose down
Super compressible
Small storage pocket for headlamp or batteries
High-quality stuff sack included
Could be a tight fit for some
Expensive

The Mountain Hardwear Phantom 0 has been tweaked and redesigned over the decades, but it remains one of the highest quality bags on the market and is still highly coveted by anyone who dreams of spending nights out in a wilderness of white. Featuring 850-fill power down in a 10D recycled nylon shell, this highly compressible, sub 3-pound bag is perfect for winter backpacking trips and overnight ski tours. Speaking of compression, MHW pulls out all the stops, including a high-quality compression sack with this bag. Our testers appreciate the DWR treated shell fabric that keeps the down dry and protected from condensation, and they also love thoughtful features like the storage pocket and glow-in-the-dark zipper pulls.

Though the cut of the Phantom 0 is standard compared to most of the top-performing down bags, larger folks may find it a little tight, especially if they're spending multiple days in a base camp situation, keeping a liter of water, a set of clothes, or even their boots in the bag with them. There's also no getting around the price on this bag, as quality goose down just doesn't come cheap, especially when it's encased in a lightweight and durable shell fabric. Hopefully, if you pony up for the Phantom, your excuses not to get out in the backcountry this winter will disappear, as will any buyer's remorse. We'd bet on it.

Read review Mountain Hardwear Phantom 0

Best Bang for Your Buck


REI Co-op Down Time 0


REI Co-op Down Time 0
Best Buy Award

$239.00
(8% off)
at REI
See It

48
OVERALL
SCORE
  • Warmth - 20% 6
  • Weight - 20% 2
  • Comfort - 20% 6
  • Packed Size - 15% 4
  • Features - 10% 6
  • Weather Resistance - 15% 5
Weight: 3.87 lbs | Fill: 27 oz of 650-fill down
DWR-treated shell fabric
Under 4 lbs
Comfortable draft collar
Affordable
Heavy

The REI Co-op Down Time 0 is a down bag for everyone that easily outperforms similarly rated and priced synthetic bags. Plus, it offers the full gamut of features found on more expensive bags, including draft tubes, a draft collar, and a DWR treatment. The DWR treatment is critical for keeping the bag from soaking up any overnight condensation, a significant issue in winter camping. This bag arrived loosely packed in a large storage sack, a good sign that the 650-fill duck down isn't stored in a compressed state and a nod to REI's commitment to quality, even when handling the less expensive duck down.

While acceptably warm for its price, the Down Time 0 is not lightweight. The 650-fill duck down is warm, but its warmth-to-weight ratio is not anywhere near as good as bags with 800+ fill goose down (but those are more than twice the price). Lugging this bag miles into the mountains is a chore, but for winter time car camping or shorter excursions out to the hunting camp, this is a great choice.

Read review REI Co-op Down Time 0

Best for Lightweight Winter Adventures


Western Mountaineering Versalite 10


Western Mountaineering Versalite 10
Top Pick Award

$590.00
at Backcountry
See It

69
OVERALL
SCORE
  • Warmth - 20% 5
  • Weight - 20% 9
  • Comfort - 20% 6
  • Packed Size - 15% 9
  • Features - 10% 6
  • Weather Resistance - 15% 6
Fantastic warmth-to-weight ratio
Narrow cut for thermal efficiency and weight savings
Awesome snag-free zipper
Not as resistant to rain and snowmelt
Impressive warmth falls noticeably short of heavier models

The Western Mountaineering Versalite is our go-to bag for ultralight winter adventures. Weighing in at a scant 2 lbs 1 oz, this bag has a great warmth-to-weight ratio and is fantastic for spring ski tours and chilly climbing trips. As with all Western Mountaineering bags, the Versalite has an excellent snag-free zipper, a lofty draft tube, and a warm draft collar. Paired with a down jacket, the versatile Versalite is a great choice for those who tend to sleep warm and want to cut weight.

The Versalite isn't as weather-resistant as some of the heavier bags in this review, but it packs down smaller and weighs less than every bag in its class. If you're going to be facing temperatures consistently colder than the mid-teens and below, we'd suggest carrying a warmer or heavier bag, like the Mountain Hardwear Phantom 0 or the Western Mountaineering Kodiak. If not, this bag is worthy of falling in love with.

Read review Western Mountaineering Versalite

Best for Comfort


NEMO Sonic 0


NEMO Sonic 0
Top Pick Award

$479.95
(4% off)
at Backcountry
See It

71
OVERALL
SCORE
  • Warmth - 20% 6
  • Weight - 20% 6
  • Comfort - 20% 9
  • Packed Size - 15% 6
  • Features - 10% 9
  • Weather Resistance - 15% 7
Roomy
Unique vents for releasing some heat
Versatile
Comfortable for many different sleeping positions
Not as warm as other bags rated to the same temperature

The Nemo Sonic earns a spot in the winner's circle for its comfort. The generously wide-cut gave our testers plenty of room to toss, turn, and sprawl inside this bag. Thermal vents allowed us to dial in just the right amount of warmth for a wider range of usefulness (though through most of our testing, it was so cold we opted to keep them closed). Additionally, the deep hood, wide shoulder cut, and elastic foot box allowed our testers to change clothes while still inside the bag.

Our testers feel like the Sonic isn't as warm as some of the other 0-degree F bags in our review, most notably the Western Mountaineering Kodiak MF. Because of the extra room, this bag isn't as thermally efficient as some of the tighter fitting bags. A good way to add a little warmth is to stuff your puffy jacket in the bottom of the bag to fill up the extra space. If comfort is your top priority, this could be the bag you've been looking for.

Read review Nemo Sonic

Best For Expeditions


Marmot Col -20


Marmot Col -20
Top Pick Award

$717.75
at Amazon
See It

68
OVERALL
SCORE
  • Warmth - 20% 9
  • Weight - 20% 3
  • Comfort - 20% 7
  • Packed Size - 15% 5
  • Features - 10% 9
  • Weather Resistance - 15% 9
Super wide cut for storing boots, water, or extra clothing
Weatherproof
Reinforced inside the toe box to resist damage from boots
Heavy
Takes up lots of space in a backpack

The Marmot Col is a great bag for expeditions, where you'll likely spend days on end inside your sleeping bag, staying warm and waiting for good weather. This bag has plenty of room to store water bottles, boots, extra clothing, and anything else you don't want to freeze. This bag is so spacious that one of our testers found he could even read while remaining completely inside.

The Col weighs over 4 pounds and doesn't pack down as small as lightweight bags in our review, so this isn't the best choice for long-distance human-powered activities. This is a better choice for folks getting around on a snowmobile, horse, or dogsled. If comfort, weather resistance, and warmth take priority above weight and packability, the Col is a perfect choice for your winter base camp.

Read review Marmot Col -20


Why You Should Trust Us


This review is brought to us by Matt Bento and Jeff Rogers. Matt has spent more of his life in a sleeping bag than he cares to admit, working in wilderness therapy, as a backpacking guide, and during his personal backcountry climbing pursuits. He's used roomy bags for weeks of living out in the snow and more lightweight bags for alpine missions in the Sierra. An ambitious skier, Jeff has many big ski descents under his belt, traveling everywhere from Alaska to Bolivia to pursue big lines. These adventures take him deep into the backcountry, where he appreciates a sleeping back that is light and warm.

Discovering the best down bags began with scouring the market for the most popular models. Then we purchased and evaluated the top candidates, scoring them with our metrics of warmth, weight, comfort, packed size, features, and weather resistance. We tested these bags primarily in the Sierra Nevada mountain range of California while also taking them on trips in New England in the dead of winter. After 100s of zipped zippers, packed backpacks, and plenty of chilly nights under the stars, we feel confident in our recommendations.

Click to enlarge
Click to enlarge
Click to enlarge

Analysis and Test Results


A key piece of gear in every person's overnight winter kit is their sleeping bag. Without it, you will likely succumb to the extreme cold while trying to catch some sleep. Another great way to visualize your sleeping bag is that it's your "survival capsule." Say you were to rip a hole in your tent or break your leg far away from the nearest help, your sleeping bag will likely be the difference between getting rescued or becoming hypothermic waiting to be rescued. In most situations, you just need the ability to burrow inside a lofty down cocoon at the end of a cold day and get warm. Remember, there is often no other heat source except for your body heat in most winter trips; building fires isn't always an option. Thankfully, modern down bags allow us to stay alive and even sleep comfortably in the coldest conditions with waterproof/breathable fabrics, hydrophobic down, and various clever design strategies. The ability to not only fall asleep but also rest and recover adequately is key to enjoying any of the skiing, hiking, or climbing you plan on doing during your trip. Shivering all night and surviving is one thing, but slumbering into a deep sleep to wake up refreshed is another.

Our review selection includes bags that will keep you warm and comfy in the parking lot of your favorite winter crag, as well as high-end, lightweight bags suited for climbing expeditions and backcountry ski tours. We brought back some tried-and-true favorites from our previous review and pitted them against a range of newcomers. Each bag was evaluated for its warmth, weight, comfort, packed size, features, and weather resistance.

Quite a colorful, lofty bunch of sleeping bags ready for our testers...
Quite a colorful, lofty bunch of sleeping bags ready for our testers to analyze.
Photo: Jenni Snead


Value


A key part of purchasing a new winter bag is ensuring it fits within your budget constraints. While we don't factor value into a product's score in this review to remain objective about performance, we understand that this is a top consideration for most buyers. A big trade-off in this category is the quality of the down fill and the loft it provides. If you're paying less, the bag will generally weigh more and loft less, leading to a heavier pack and a less warm bag. But, to save a few hundred dollars (or more), you might be willing to haul a tad more weight and sleep with your puffy on (which is more than likely with you on any winter trip). This is a personal choice, but one worth wrestling with. Also, consider the use case of this sleeping bag. Being as realistic as possible, how often are you sleeping in this bag? Once or twice a year? Ten times a year? 50 times a year? A top-dollar sleeping bag may not seem like much of an expense when you divide its price by 50 nights.

Alternatively, if you're only using it a couple of times a year, you don't need the highest-end materials and fabrics. The REI Co-op Down Time is heavier than the top brass in this category but will keep most winter campers sufficiently toasty and cozy without breaking the bank. While it's a touch more expensive than the Kelty Cosmic Down 0, we think it's worth this tiny price bump for better overall performance.

Warmth


A sleeping bag's warmth stems from a few different factors. The bag's fill power, the fill weight of the bag, and the cut of the bag most dramatically affect how warm a sleeping bag is. A bag with a high loft (a combination of fill weight and fill power) will keep you warmer because there will be more insulated air between you and the cold air outside. This insulated space allows you to create a warm microclimate with your body heat. The bag's cut or fit determines the dimensions of the shoulder, hip, and foot box, which can feel tight or roomy depending on a person's body shape. Extra space can be useful for accommodating additional layers you may want to wear or items you want to keep warm with you through the night, like water bottles, radios, headlamps, phones, white gas, stoves, boot liners, and batteries. However, with the added airspace a larger cut bag provides, there is more uninsulated space inside the bag, and it is less thermally efficient. It will take longer to bring the sleeping bag from the ambient temperature to a suitable body heat temperature and feel warm inside. You will also have an easier time noticing any drafts that make it past the draft collar.


The warmest bags in our selection are the bags with the most loft and the most fill material. The Marmot Col -20 houses an impressive 44 oz of 800 fill power down and features a wide cut, with plenty of space for wear/storing extra layers. Our testers found they could even change clothes inside the bag. This is a bag geared toward more extreme temperatures that the vast majority of winter campers are less likely to experience, though, so its extra warmth might not be necessary.

The Marmot Col is incredibly lofty with 44 ounces of down fill.
The Marmot Col is incredibly lofty with 44 ounces of down fill.
Photo: Jenni Snead

The Western Mountaineering Kodiak MF feels less warm while being much lighter than the Marmot Col. It has less room but is significantly wider than the similarly rated Snowbunting and Antelope. It is a great option for those who value roominess and want to have plenty of insulation to keep them warm at 0F.

Somewhere in all that lofty goodness is a very warm human. This bag...
Somewhere in all that lofty goodness is a very warm human. This bag employs 30oz of 850 fill down, giving it one of the best warmth to weight ratios out there.
Photo: Matt Bento

For those looking for maximum thermal efficiency, there is the Feathered Friends Snowbunting, one of the slimmest bags in our review. The Snowbunting packs 25.3 oz of 900 fill down into a 2.85 lbs package.

The Western Mountaineering Antelope MF, the Rab Neutrino 800, and the uber comfy Nemo Sonic are similarly rated and weighted bags, but the Rab Neutrino 800 and the Antelope feel warmer than the Nemo Sonic because they both have more down and narrower fits. The Western Mountaineering Versalite, conservatively rated to 10 degrees, is the lightest bag in our review but is still warmer than the heavier Nemo Sonic due to its high loft and a narrower cut.

The Western Mountaineering Versalite (left) is 2lbs lighter than the...
The Western Mountaineering Versalite (left) is 2lbs lighter than the Marmot Col -20 due to its lightweight shell fabrics, but the Col (right) is warmer and way more weather resistant.
Photo: Jenni Snead

Less expensive bags like the REI Co-op Down Time 0, Rab Ascent 900, and Kelty Cosmic Down 0 can feel as warm as some of the higher-end bags. The good news is that you can sleep out in the lower temps at a lower price. The Kelty Cosmic Down 0 is as warm and lofty as the Rab Ascent 900, but you'll pay with your legs, back, and the space in your pack. The REI Down Time is warmer than both of these, which is a large reason it gets our attention as a stellar budget-focused purchase.

Weight


A sleeping bag's total weight is a function of its fill material and the weight of its shell fabrics. There are two important indicators in our tests: the fill weight and the weight of the rest of the bag. You can compare this ratio against other bags to see how warm the bag is for its weight. A bag with higher quality down filling (800 or more) can achieve a lower temperature rating at a lower weight. High-tech shell fabrics allow for weather resistance and durability, even in light, 12 denier shells. Light is right if you're going the distance! But it's usually very expensive.


The lightest bag in this review is the Western Mountaineering Versalite, with its super thin 12-denier Extremelite shell. The Versalite boasts 20 oz of 850 fill goose down and weighs in at 2 lbs 1 oz; it has an excellent warmth-to-weight ratio but isn't as weather-resistant as the heavier Feathered Friends Snowbunting. The welterweight Western Mountaineering Antelope MF tips the scale at 2 lbs 10 oz, similar to the Nemo Sonic, but the high-quality lightweight shell allocates more of that weight to insulation, so it feels warmer. It's important to also look at what kind of environment the bag will be experiencing. Maybe it makes sense to get a more weather resistant shell if you often face damp climates during your winter excursions.

Purchasing a lightweight bag is an easy way to lighten the load on...
Purchasing a lightweight bag is an easy way to lighten the load on your next ski tour or winter backpacking trip.
Photo: Jenni Snead

The warmest bags in our selection are also some of the heaviest. The Marmot Col -20 weighs 4.08 lbs, dedicating 21.3 oz to its tough, highly weather-resistant 30-denier Pertex shell fabric. The Western Mountaineering Kodiak MF (2.85 lbs) cuts off a few ounces while still having a wide fit and great features due to its light shell fabrics. The Mountain Hardwear Phantom 0 deserves recognition regarding its weight. It feels pretty equal to the Kodiak in warmth but weighs almost three ounces less.

Each of these bags has similar weights, but the Kodiak MF is warmest...
Each of these bags has similar weights, but the Kodiak MF is warmest because it has the highest quality down and lightweight shell materials.
Photo: Matt Bento

The Kelty Cosmic Down is the least expensive bag and among heaviest bag we tested, weighing 3.8 lbs, almost the same as the Marmot Col -20, but not even close in terms of warmth and weather resistance. The REI Down Time is very similar to the Cosmic Down in this aspect. These heavier, budget-friendly bags make for stronger legs and heavier wallets as compensation.

Staying warm and comfy while sitting up, drinking coffee, and even...
Staying warm and comfy while sitting up, drinking coffee, and even cooking is key in cold winter camping situations.
Photo: Matt Bento

Comfort


We determine comfort based on the feel of the bag against our skin, how the hood and draft collar fit, and, most importantly, how much space is in the bag. Sleeping bags with a wider cut generally received higher comfort scores. If you sleep exclusively on your back, a wide cut isn't too much of a concern. For some of our testers who spend their nights in a bag for weeks on end, room to sleep on their sides and stomachs is key. The price of comfort? Extra fabric equates to extra weight and less space in your backpack. Consider how well you perform after a poor night of sleep, and you may decide the extra weight is worth it.


The Nemo Sonic has the widest cut of all the bags; it employs a 20 denier ripstop fabric to keep the weight down from all that extra girth. Our testers found they could sleep comfortably in this bag in any position, even in the classic "can opener" position, due to the slight stretch in the middle.

Our lead tester has plenty of room to sleep on his stomach with one...
Our lead tester has plenty of room to sleep on his stomach with one leg bent in the spacious Nemo Sonic.
Photo: Jenni Snead

The Western Mountaineering Versalite and the Antelope lost points in this metric due to their shallow hoods. Our testers generally preferred the slightly deeper hood of the Kodiak with drawstrings for the hood and the draft collar. The lower scores in the comfort metric go to the Feathered Friends Snowbunting and the Kelty Cosmic Down 0. The Snowbunting and the Cosmic Down have shallow hoods and relatively narrow (but thermally efficient) cuts. These bags didn't score very high here but are by no means uncomfortable - simply average. Again, if you primarily sleep on your back, the width isn't so important. Additionally, if you're interested in the Snowbunting for alpine and big wall climbing, you'll likely be on your back anyway, sleeping on a narrow ledge or nestled among the rocks. Conversely, if you are spending weeks climbing Denali, or weeks camping in remote and cold locations, a thermally efficient cut can get tight quickly. With the added amount of items needed to sleep with and the overall longevity of time spent in your sleeping bag, it makes sense to go with a wider cut like the Kodiak or Marmot Col.

If you don't need to hike too far, this comfortable and warm bag is...
If you don't need to hike too far, this comfortable and warm bag is great for a chilly evening under the stars. We kept the fly off our tent to push the warmth limit of the Down Time on a December night in the High Sierra desert.
Photo: Matt Bento

Packed Size


Ski touring can be a gear-intensive activity, and pack space is a premium once you've accounted for a shovel, probe, food, water, layers, and a tent—ditto for alpine climbing, when you may find your pack overflowing with ropes and cams. Higher quality materials are critical for increased packability. To assess the packed size, we crammed each bag into our Sea to Summit compression sack and pulled down as hard as we could on the compression straps. We then got an accurate idea of how each sleeping bag compressed in the same stuff sack, as well as how they compressed in their own stuff sacks when the manufacturer included them.


Much to our surprise and delight, each bag fit inside the compression sack, even the hulking Marmot Col, which looks huge when lofted in its storage sack. The ultra-light Western Mountaineering Versalite predictably compresses the most. We found it easiest to compress the bags by sitting on them once they were in the stuff sack; you can then rotate the compression sack and tighten each strap. The Western Mountaineering Kodiak MF packs down to a backpack-friendly size, even though it's one of the wider and warmer bags in the review. This is why we love the Kodiak so much; a ton of loft and room with a manageable packing size.

All the bags in our review included a stuff sack, but only a few had...
All the bags in our review included a stuff sack, but only a few had compression sacks. With a compression sack, all the bags pictured here packed down even smaller.
Photo: Jenni Snead

Bags with a lower fill power down take up the most space. The Kelty Cosmic Down 0 one of the least packable, taking up more room than the Marmot Col.

Features


Features are a subjective, multifaceted metric, comparing aspects universal to all the bags, such as draft tubes, hoods, and zippers, while also factoring in characteristics unique only to certain bags. Some bags had stash pockets, which are useful for storing batteries or a watch but also can be annoying if you roll over on them. Some sleeping bags also had two zippers so you could sit up while still inside the bag. Other bags had "gills" to allow you to vent at the base of the climb, where you may not encounter conditions even close to 0F. All of these features were considered when scoring a bag.


The Nemo Sonic has a ventilation system employing two zippered gills on the top of the bag, so you can cool off when using the bag in warmer weather. We feel this is an interesting feature but do not like the fact that if the zipper breaks, you are now in a 20F bag regardless of how cold the night time low is. The Western Mountaineering bags are a standout for their awesome snag-free zippers, while other zippers snagged on the double draft tubes. A few bags had a small pocket inside the bag for keeping small items accessible and items with batteries warm. Bags with simple, effective features scored higher because features are great, but when they break, they can cause problems, and they also add weight. So if the feature set was well thought out, reliable, and didn't add significant weight to the bag, those scored the highest. The top scorers in this metric are the Marmot Col -20 and Nemo Sonic, pumping out the features.

No bag is designed to withstand full submersion, but many of the...
No bag is designed to withstand full submersion, but many of the bags proved highly water resistant. Here we were able to squeeze the air out of The North Face Inferno, but only a minuscule amount of water got in.
Photo: Jenni Snead

Draft collars are key for keeping out the cold. We found the cinch...
Draft collars are key for keeping out the cold. We found the cinch cord easily accessible on the REI Down Time, making midnight adjustments easy.
Photo: Matt Bento

Weather Resistance


Due to the variety of conditions that can be encountered on a climb, a sleeping bag must be able to withstand wet weather. Condensation from tents, frost from your breath freezing on the inside, and even a light rain shower are all realities your sleeping bag might face on a multi-day climb. When down gets wet, it loses its loft because the down clusters can no longer trap air. This results in a total loss of insulating properties.

Alternatively, if a bag can withstand the elements well enough on its own, you get a bonus weight savings since you don't have to bring along a bivy sack or a tent. A sleeping bag's weather resisting abilities boil down to shell fabrics. The variety of shell fabrics on the market make some down sleeping bags suitable for use out in the open, others made for the shelter of a tent. Some of the bags feature specially treated hydrophobic down.


The manufacturers claim hydrophobic down absorbs less water and maintains its loft better, and dries out faster than untreated down. Our testing team could distinguish a difference between treated and untreated down in some of the sleeping bags with a more delicate face fabric. We found that the sleeping bags with a thick waterproof shell didn't seem to need hydrophobic down as it was hard to get the down inside the bag wet at all, short of sticking the garden hose inside the bag. They were just that waterproof. The Rab Neutrino 800 and the Rab Ascent 900 feature down with a hydrophobic treatment.

The Marmot Col -20 is king when it comes to combating the adverse weather. Its burly, waterproof shell absorbed zero water, even in our submersion test. The Feathered Friends Snowbunting falls right behind the Marmot Col. These contenders kept our testers warm and dry in light rain. And something to note, none of these bags contain hydrophobic down. The best bags for cowboy camping just have excellent shell fabrics. Even the lightweight Western Mountaineering bags were impervious to light rain and condensation. We want to stress how high tech these fabrics are nowadays and that you don't need a full membrane for most applications.

Cold rain is no match for the Feathered Friends Snowbunting...
Cold rain is no match for the Feathered Friends Snowbunting (foreground).
Photo: Jenni Snead

Only the Kelty Cosmic Down 0 absorbed enough rain to soak through to our testers. If you decide to purchase this warm, budget-friendly bag, make sure you've got an effective way to keep it dry, like a tent or the back of your car.

The Kelty Cosmic Down was the only bag to wet through in our rain...
The Kelty Cosmic Down was the only bag to wet through in our rain testing due to its sewn through construction.
Photo: Jenni Snead

Accessories


A stuff sack and a storage sack are included with each of the bags in this category, with the exception of the Kelty Cosmic Down 0, which only comes with a stuff sack. The Western Mountaineering bags have the largest storage sacks so that you can store them at the maximum loft. The Rab Ascent 900 and Nemo Sonic include a stuff sack with compression straps, and the Rab Neutrino 800 comes with a dry bag. Additionally, some sleeping bags come with a compression sack, which is useful for getting the smallest form factor out of your sleeping bag. Alternatively, in some conditions stuffing the bag directly into the backpack can yield the best results. Be sure to purchase a quality pad that will keep your body warmth in. All the expensive, high-quality down is useless if it's compressed underneath your body, with only a thin shell layer between you and the frozen ground. You'll need a pad that's light, durable, and insulates well to complement a winter down bag. Look for an r-value of at least 5, which can be achieved with a foam pad underneath and an inflatable pad in combination. Alternatively, there are some high-end sleeping pads that do not require the addition of foam underneath.

A warm down bag is crucial for a good night of sleep, so that you...
A warm down bag is crucial for a good night of sleep, so that you can feel rested and ready for winter sports action. Here our lead tester is psyched to get up and go skiing.
Photo: Jenni Snead

Conclusion


We hope we've unraveled some of the mysteries around selecting the best cold weather down bag to suit your specific needs. While a down bag may seem like a huge financial investment, it should keep you warm and cozy for years if properly cared for, and nothing beats a good night's sleep under the stars on a long winter's night. So say our testers, at least.

Matt Bento and Jeff Rogers