First, if you're unsure about whether an ultralight product is right for you, our Buying Advice article for traditional backpacking sleeping bags provides a detailed analysis of the categories we test and score. This incredibly thorough overview covers types of insulation, shell fabrics, and construction techniques, as well as different styles of bags and their best uses. In order to not be redundant, the below article focuses on styles, features, and strategies that are particular to ultralight sleeping bags, and doesn't repeat the useful basic information relevant to all sleeping bags.
Choosing the Right Sleeping Bag
It is the intention of this article to walk you through a decision making process that will result in you choosing the perfect sleeping bag for you. This involves asking yourself a series of questions that will best help you identify your needs and desires, and also rule out any particular bags or styles that are going to be completely inappropriate for your adventures. The end result should be a very narrow focus of products that you can then research in more depth before making your decision.
Why Choose an Ultralight Sleeping Bag?
When we first started backpacking about 28 years ago, it was very common to head out on week-long trips with a frame backpack full of 50 or more pounds of gear, and wearing a big ol' pair of heavy hiking boots. That was just the way most folks went about it, and was certainly the way we were trained by the Boy Scouts. Today, not only is there much more advanced gear, but lots of backpackers and climbers recognize how much easier it is on your body to carry a light load. Anyone who has ever been backpacking can tell you a story about the relief they felt when they took off their enormous pack, and the dread that came each morning when it had to be donned once again. Imagine carrying a pack so light you don't ever feel like you need to remove it! Simply put, traveling light is much less arduous, and therefore much more fun. In addition, if you want to cover a lot of mileage each day or you're carrying your overnight kit up a technical climb, there is no arguing that light is right.
While ultralight sleeping bags are ideal for use while backpacking, they are also great for all of the many outdoor sports that require a "light is right" ideal. Especially in the last few years, ultra-endurance activities have seen a surge in popularity. Long distance thru-hiking, bike-packing, fast-packing, and bike touring have become somewhat commonplace, and ultralight sleeping bags are just one of the pieces of lightweight kit needed to make these adventures happen.
How Can a One-Pound Sleeping Bag be so Warm?
On average, the ultralight sleeping bags and quilts we review weigh half of what backpacking sleeping bags weigh, but usually deliver similar warmth. How is that possible? Most of the bags we tested use the most advanced lightweight materials and the highest quality insulation. However, the materials are only one key part; how the sleeping bag is used is equally important.
Most thru-hikers and alpinists sleep in most or all of their warm clothing on cold nights. Not only are they dressed and ready to go for a pre-dawn start, but they can also get away with a lighter sleeping bag. Ultralight enthusiasts also know how to pick campsites with a warm microclimate or protection from the wind. Ever put in your camp right in the bottom of the valley, only to walk a few hundred feet up the hillside at dawn and realize it's a good 10 degrees warmer up there? Choices like this one can make a huge difference in whether or not you stay warm enough to sleep through the night. Hot drinks before bed and at dawn, a Nalgene full of boiling water to preheat your bag, a set of crunches to ramp up the blood flow to the extremities these are all tricks we use for a comfy and warm night's sleep.
Types of Ultralight Sleeping Bags
Ultralight sleeping bags generally fit into two different categories based on their design: Mummy Bags or Quilts. However, there are many variations of these two simple designs, and hybrids also exist.
Mummy bags are the most traditional and common style of three-season sleeping bag. All of the bags in our Backpacking Sleeping Bag Review are mummy bags. They are designed to enclose you completely like a mummy, and are shaped just like the Pharaohs you can see at the museum. They are narrow at the feet and legs and wider through the torso. Most mummy bags have a large hood that will fully cover your head and can be cinched tight around your face to allow only the tiniest opening to breathe through, thereby giving you the very best protection against the cold. Mummy bags help you stay warm by only leaving a small amount of space inside the bag that is unfilled by your body, meaning less air to heat. This also makes them feel constricting and claustrophobic to some. They also tend to be the warmest options available. Seven of the 11 bags we tested for this review incorporated aspects of the mummy design.
Hooded Mummy Bags
The Patagonia 850 Down Sleeping Bag 30 and The North Face Superlight 15 are classic hooded mummy bags that are very light for a three-season mummy bag, but are among the heaviest in this review. They are also the two warmest bags we tested.
On the other end of the spectrum are the Sea to Summit Spark I and the Western Mountaineering HighLite, which are also both hooded mummy bags, but are the two lightest bags in this review. They are only suitable for the warmest of temperatures, as the way they are so light is by including less insulation and having a higher temperature rating.
Hoodless Mummy Bags
The Zpacks 20 Degree and the Feathered Friends Vireo UL are hoodless mummy bags, meaning they are shaped like a mummy, but do not have a hood. This is one way that they trim off a few precious ounces. The Zpacks 20 Degree has a classic ¾ length zipper and enclosed foot box, so if it is hot you can unzip it all the way and it acts like an enclosed quilt. On the other hand, the Vireo UL is a zipper-less bag altogether, meaning you have to wriggle yourself down inside it, and it also saves weight by having less insulation around the torso, assuming that you will pair it with a warm insulated jacket.
Down quilts are a versatile solution to the feeling of constriction that is inherent in a mummy bag design. They also manage to save weight by not including as much material or insulation, and also nixing the hood and zipper. The basic premise is that in order to be an effective insulator, down needs to be able to loft up and create space that traps air. When you are sleeping on top of down it is fully compressed, thereby losing the vast majority of its insulating abilities. Rather than carry the extra weight and bulk of that "wasted" down insulation and fabric that is enclosing it, why not simply forego having an underside to the sleeping bag altogether? Interestingly, despite the logic of this argument, ultralight quilts in this review were not statistically lighter than their mummy counterparts (they are still much lighter than traditional non-ultralight mummies). However, they do allow for a great range of comfortable sleeping styles and the ability to either wrap oneself up in the cold, or spread out and ventilate in the heat. Six of the bags tested in this review were quilts.
An interesting feature found on most quilts that is not found on mummy bags is a sleeping pad attachment system. In order to stay comfortably wrapped around you so that warm air does not escape and cold air does not infiltrate your comfort envelope, manufacturers have devised different systems of straps that wrap underneath a sleeping pad and attach to the sides of the quilt, holding it in place. In our experience, the functionality of these attachment systems ranged from "awesome" to "useless." The quilts we tested came in two basic designs: foot box enclosed, or full blanket. They are described below.
Enclosed Foot Box Quilts
For added warmth around the feet, some quilts have fully enclosed foot boxes, and the blanket aspect of the design starts roughly a foot up from the feet. This design tends to be a little bit warmer, and also simpler as there are less features like drawcords and zippers needed to enclose the feet, but are slightly less versatile than a full blanket design. The Sierra Designs Backcountry Quilt 700 and the Katabatic Gear Palisade 30 each used this design. When the zipper is fully opened up the Zpacks 20 Degree also acts as an enclosed foot box quilt.
Three of the quilts we tested open up into a full blanket, meaning the foot box is not fully enclosed. These were the Feathered Friends Flicker 40 UL, our Best Buy winning Enlightened Equipment Revelation 20, and the Sea to Summit Ember II. The Flicker 40 UL is the most versatile bag that we tested, as it also has a full length zipper so it can be enclosed like a mummy bag, but does not come with a pad strap attachment system. On the other hand, the Revelation and Ember II both have pad strap systems and are designed to be used that way. All of these blankets have draw cords at the feet that cinch all the way up to fully enclose the feet on cold nights.
Safety & Warmth
Your sleeping system, along with your shelter to keep it dry, is your primary safety net while deep in the backcountry. On your quest to lighten your load, this should always be in the back of your mind. No! Actually, it should be right up front. Our testers who have thru-hiked big trails want us to emphasize this point - it can take a LOT of experience to use a 10 pound backpacking kit in threatening conditions.
When the weather takes an unexpected turn for the worse, you have two options: hunker down and wait it out or stay on the move for what could be hours or even days. In order to stay safe with your ultralight kit, you must know how to use your shelter plus sleep system to make it through a long unexpected storm. Two days and nights of cold rain (or even snow) are always a possibility, even in the summer, in most mountains. And we often hear folks say "well if my bag gets wet or I can't pitch my tarp, I'll just keep hiking to stay warm until the weather clears." But can you do this in the dark? Or in weather that makes it hard to see and navigate? Make sure your skills and systems will see you through hunkering down to wait out storms. Practice a lot. Spend nights out in terrible weather close to your home or vehicle to prepare.
If you have doubts about what warmth rating is appropriate for you, choose a product that is warmer than you think you will need. As we discussed in the warmth section of our main Best In Class review, be aware that temperature ratings listed by a manufacturer may not always be accurate. However, they should give you a general ballpark figure for the coldest nights you would want to sleep in that bag. If you are a cold sleeper or have doubts whether you may face colder temperatures, we recommend carrying a few extra ounces and having a slightly warmer sleeping bag. Every bag tested in this review comes with different temperature options (although they may not always be called the exact same thing). For example, our Editors' Choice winning Feathered Friends Flicker 40 UL also comes in 20F and 30F versions. While we ordered the 40F for testing in order to have the lightest version available, for sleeping in the high mountains of Colorado, we would certainly order a warmer version next time.
Also keep in mind the limitations of your preferred style of sleeping bag. For example, quilts that attach to sleeping pads rely on the insulating properties of the pad to complete the comfort envelope. This means that on a cold night you could have a 30 degree bag that is more than sufficient, but a minimally insulated air mattress beneath you that is conducting cold air into your body, meaning you may still be cold. An extra layer of protection, like a lightweight Bivy Sack or a fully enclosed tent can help you in these situations, and also give you a larger margin of safety if bad weather strikes.
Down & Moisture
We purposely selected all down insulated products for this review. Down has a significantly better warmth-to-weight ratio than synthetic insulation, but has one main drawback. It must be kept dry to maintain its loft and keep you warm. We can't emphasize this enough: keeping your sleeping bag dry and taking every opportunity to air it out in the sun is critical to your warmth and safety. If you exclusively backpack in environments that are very rainy, consider paying the weight penalty and using a synthetic insulated bag or quilt. Increasingly, ultralight manufacturers are producing quite light synthetic insulated bags and quilts.
Increasingly, manufacturers are using hydrophobic down in their products, which is down treated with a DWR coating for added water resistance. There are a lot of claims about the efficacy of this treatment, and we recommend you check out the findings of our tester Ian Nicholson in his Buying Advice article for Backpacking Sleeping Bags. The short summary is, while purchasing a bag with hydrophobic or treated down can't hurt, we don't recommend that you rely on it to save you in a downpour. Products in this review that are filled with hydrophobic down are the Sea to Summit Spark I and Ember II, the Sierra Designs Backcountry Quilt 700, the Katabatic Gear Palisade 30, and The North Face Superlight 15.
Another nice feature to look for is a DWR coating on the shell fabric of the sleeping bag, or bags made with a shell fabric that is naturally water resistant, like the Pertex Quantum fabric. While these coatings should again not be relied upon to keep a bag dry when it is wet outside, they can be nice for helping to prevent absorption of water due to condensation inside a tent, especially around the foot of the bag. It is also possible to apply your own after-market DWR coating when you wash your down bag (see the care instructions at the end of this article for advice on doing so).
Stuff Sacks: Only one of the bags in this review comes with a waterproof stuff sack, the Zpacks 20 Degree. We highly recommend purchasing an after-market waterproof stuff sack for your bag. OutdoorGearLab has an entire article dedicated to the Best Sleeping Bag Stuff Sacks. In addition, many backpackers will line their entire pack with a waterproof liner. A heavy duty garbage bag, or better yet, trash compactor bag works great. If you're going be out for weeks or months, consider purchasing a durable and waterproof Cuben fiber pack liner. ZPacks makes excellent pack liners as well as stuff sacks. Find the complete selection here.
Your Ultralight Sleeping Bag as Part of a System
When building your kit for ultralight backpacking, your focus will be on selecting complementary products and systems that lead to an overall light Base Weight. You can read about the fine details of systems and base weight over here in our ultralight tent article.
Your "Big Four" items when building your kit include a sleeping bag and sleeping pad, along with your backpack and shelter. These are usually the heaviest four items a three-season backpacker carries, and the most important for nighttime weather protection, warmth, and safety.
Sleeping System Examples
Here are a couple sleep system examples and how they can be paired up with shelters of similar value. The first is for folks seeking the lightest and warmest set-up without regard to price and the next is focused on "bang for your buck" products. Choosing components with the best warmth-to-weight ratios means you could also add a super light bivy sack to your sleep system and still stay under 2.5 lbs.
Zpacks 20 Degree: 20.3 oz, $415
Therm-A-Rest NeoAir XLite: 12.0 oz, $130
Total: 2 lb. 0.3 oz and $545
With the Mountain Laurel Designs Superlight Cuben Bivy: 4.8 oz, $245
Total with MLD bivy: 2 lbs, 5.1 oz and $790
Pair this sleep system up with the Hyperlite Mountain Gear Square Flat Tarp: 10.2 oz, $340
Sleep plus Shelter Systems Grand Total: 2 lbs, 15.3 oz and $1,130
Carry this expert level kit in the Zpacks Arc Blast 52: 21.3 oz, $295
Big Four Grand Total: 4 lbs, 4.6 oz, and $1,425
This expert level ultralight kit, with the price tag to match, has the added protection of a bivy sack (and it would weigh in under 4 lbs. without). Every thru-hiker we know would be psyched to use this kit.
Enlightened Equipment Revelation 20: 19.3 oz, $270
Therm-A-Rest Z Lite Sol: 14.0 oz, $35
Total: 2 lbs, 1.3 oz (33.3 oz) and $305
Pair this sleep system up with the Mountain Laurel Designs Grace Tarp Duo: 19.1 oz, $170
Sleep plus Shelter System Grand Total: 3 lbs, 4.4 oz and $475
Carry this kit in the Osprey Exos 48: 33.9 ounces, $190
Big Four Grand Total: 5 lbs, 6.3 oz, and $665
These systems demonstrate not only how expensive it can be to shave ounces from your ultralight set-up, but that the investment can lead to a more protective, warm, and comfortable kit. Lots of folks have successfully thru-hiked long trails with systems similar to both of these. The main advantage of the premium system is an added safety margin if you choose to add a bivy sack, or the weight savings if you forgo it. The top-of-the-line bag and pad combo is exactly twice as expensive as the budget focused combo, but it saves you 5.1 ounces and is both warmer and more comfortable. This weight savings allows including the added weather protection and safety of a bivy sack for the same weight as the budget-focused bag and pad combo.
Care & Feeding of Down Sleeping Bags
As we have discussed above, taking every opportunity to make sure your ultralight sleeping bag stays as dry as possible is critical to maintaining loft and warmth on multi-day trips. Long-term care will ensure the best possible life span and performance. After long trips (or at least once a year), you should launder your bag. You can do it yourself relatively easily (we usually do), but several manufacturers offer professional cleaning services. The Feathered Friends Washing Service is one example.
To get started, find a large, front-loading commercial washing machine. Most laundromats will have them. A top loading washer with an agitator can damage down garments don't do it. You'll also want to round up a down-specific soap like Nikwax Down Wash to take with you. Spot clean any really dirty areas of the shell material first with a cotton cloth and then turn your bag inside out. Use your down specific soap on the normal cycle with cold water for all cycles. Select a second rinse if that is an option, or run another full cycle after the first with no soap. Now you have a clean but wet bag and drying it is the most time consuming step.
Move your wet bag to one of the big front-loading commercial dryers. Ideally, you will have used it immediately before for some other laundry to verify that the medium or medium low setting is indeed accurate. Your completely wet down bag will be very clumpy, so here's where a trick helps. We either throw a few tennis balls in with the bag (or a very clean pair of running shoes). While the bag tumbles and tumbles on medium heat, these items will help break up the wet clumps of down. You can also stop the dryer periodically and break up clumps by hand. And that's it. Just make sure you've identified a dryer that will not get too hot and damage the synthetic fabric of your bag. This is the perfect time to reapply a spray-on DWR treatment to your bag. We hit the foot area of the bag thoroughly after a wash. Make sure your bag is absolutely dry before storage. We tend to do this operation on a sunny day where we can lay the bag out in the sun for the DWR to dry for a couple of hours and then stick it back in the dryer on last time to be sure.