The 3-season category is the Goldilocks temperature range for sleeping bags. We define 3-season bags as for temperatures between 15ºF to 29ºF degrees. This range is where most camping takes place. A 3-season bag can be used in summer at high elevations where the nighttime temps are frigid in addition to warm, low elevation camping. It can also transition into the cool nights of spring and fall. If we were only going to own one sleeping bag, it would be a 3-season model because it is the most versatile and will perform well in most situations.
There are two interesting trends in this category that we explore in our review: backpacking quilts and bed-style sleep systems. Backpacking quilts are designed to be lighter and more compressible than your average mummy-style sleeping bag. They dispense with hoods and zippers to keep the weight low and the packed size small. Backpacking quilts will be most appealing to long-distance hikers, lightweight backpackers, and people with more experience overnighting in the outdoors. At the opposite end of the spectrum are bed-style sleeping bags, which aim to be less confining and more comfortable than a mummy bag as they mimic the feel of sleeping in an actual bed. These products greatly enhance sleep comfort but tend to be a little heavier and bulkier than a regular bag. Bed-style bags will be more appealing for people who hate the standard sleeping bag shape, those who don’t often sleep outside, and beginner backpackers.
To initiate this review, we spent hours identifying the most popular products and researched all the new innovations being developed. We were rewarded with the opportunity to test four new-for-2019 sleeping bags. In total, we called in eight models that we think represent the best-of-the-best in the 3-season sleeping bag category. Then we assembled a team of eight testers of different genders, age, and outdoor experience to use and then report their opinions of these products. In order to truly test them, these bags traveled the world, from the Bugaboos in Canada to Cochamo in Argentina to a multi-day ascent of El Capitan in Yosemite National Park.
Editor’s note: When comparing product review scores, keep in mind that different testers have a different scoring methodology, so head-to-head scores from year-to-year are not always perfectly balanced. For best results, compare tests within each yearly test cycle (for instance, the 8 products from 2019).
When reviewing the specs and tester opinions of all the sleeping bags in this review, we realized that the Z Packs Classic Sleeping bag has the highest warmth-to-weight ratio of all the bags in our three-season test. It is a backpacking quilt that lacks a hood, but zips fully closed along the back. It is also overstuffed with down, creating a luxurious cocoon of warmth. Both the Therm-a-Rest Vesper and the Feathered Friends Tanager come really close to the warmth-to-weight ratio of the ZPacks bag, being slightly lighter weight but also a tad less warm. The Z Packs bag is less expensive than those other two contenders, making it a better deal overall. As a result, the Z Packs wins our Best in Class award by a single point. We love this thing.
It was a very close call between the ZPacks Classic Sleeping Bag and the Therm-a-Rest Vesper for our Best in Class award. Both are lightweight hoodless backpacking quilts and both compress to a very small size. The Vesper comes with a compression sack that cinches it down to roughly the size of a water bottle. Ultimately the ZPacks bag won by one point because it is a little bit warmer, but we love the Vesper. It does not have a zipper and features a fully open back with a huge draft collar with a secure snap. It is packed with Nikwax Hydrophobic down, and we did put this to the test. After getting doused by rain and remaining warm in the Vesper, we can vouch that this water-resistant coating works.
For the ultralight backpacker, thru-hiker, or mountaineer, the Tanager is a blessedly simple and lightweight product. As with all Feathered Friends products it is well constructed and filled with high quality, compressible down. This was the lightest product in our three-season test, weighing only 1 lb., 2.6 oz for a regular length. It manages this low weight by eliminating the hood and zippers, leaving just an insulated tube to sleep in. It is also constructed with a featherweight 7-denier shell. For the weight-conscious, this bag is hard to beat.
Our female testers loved this bag. It is lightweight, fluffy, very warm, and packs super small. The hydrophobic down makes it even more versatile and reliable and the fit and cut, which is wider in the hips and narrower at the shoulders, is ideal for the average lady. Its EN warmth rating is for higher temperatures than any other bag in this three-season test, but the weight and bulk remain among the lowest. The fact that it comes with an excellent compression sack that squishes the bag into a tiny bundle is a bonus. For women in search of a three-season bag for backpacking, this one comes highly recommended.
The ZenBivy Bed is a multi-piece, bed-style sleep system that offers comfort similar to your bed at home as well as versatility for sleep position and temperature. We often used the quilt on its own as a blanket around the campfire, when van or truck-bed sleeping, and even as a throw-blanket around the house. For car-camping or short backpacking trips, this sleep set-up is incredible and comfortable. For long-distance hikes or trips where every gram counts, we wouldn’t suggest the ZenBivy because it is heavier and bulkier than other options. If minimalist backpacking comprises only a small part of your camping itinerary, then the ZenBivy is an ideal choice because the quilt can be brought on its own for the occasional fast and light trip. Finally, ZenBivy is exceedingly affordable. At $269 it is the second least expensive product in our three-season test. At this price, you aren’t taking a big risk on a product that you might not like or that you might only use for half of your camping trips. If you want to invest in backcountry comfort, you won’t find a better option for less money.
A top-notch 3-season sleeping bag, which we define as one in the 15ºF to 29ºF range, needs to a achieve a difficult balance: it has to be warm for cold nights but also should ventilate for warm nights. Ideally, it should be lightweight and pack down very small so that it can fit into a backpack and not be burdensome to carry for multiple nights in a row. On top of all that, we hope that it is comfortable and durable. Our favorite bags were the ones that achieved an impressive warmth-to-weight ratio. We like it when our sleeping bags are light to carry but warm for sleeping.
For this review, we had the opportunity to test a good cross-section of the 3-season bag market. We evaluated lightweight down bags and wet-weather ready synthetic sleeping bags. We tested a range of shapes and designs, including standard mummy bags, backpacking quilts, and bed-style sleep systems. We even reviewed a women’s specific model alongside the unisex models to see what is different about a gender-specific product.
Evaluating the warmth, comfort, and durability of the Sea To Summit Women’s Flame III in the High Sierra backcountry.
Weight
For most backpackers, the primary consideration when selecting gear to carry is how much does it weigh? A sleeping bag is one of the big three items (along with a tent and backpack) that most affect the weight of your backpacking set-up. This means that the weight of this product should be carefully considered. To effectively compare the weight of all of our test products, we weighed each one on our own scale. In some cases, this was a little misleading because we tested a size a long in one model and we tested a prototype that had a heavier liner than the final product. However, this did give us an excellent baseline for comparison.
The lightest of all was the Feathered Friends Tanager, which is a hoodless, zipperless bag. It is not a quilt, because it does not open in the back, instead, it is a single continuous tube. This bag weighs 1 lb, 2.6 oz for a size regular.
The Feathered Friends Tanager was the lightest bag in our 3-season test, weighing a mere 1 lb 2.6 oz. This bag features a minimal design with no hood and no zipper. It can be used in combination with a lightweight hooded down jacket for increased warmth.
Closely behind the Tanager for weight were the ZPacks Classic Sleeping Bag (1 lb, 4.6 oz) and the Therm-a-Rest Vesper (1 lb, 4 oz). Both of these are backpacking quilts that lack a hood. The Sea to Summit Women’s Flame III is close on the heels of these innovative quilts, weighing in at 1 lb, 7.8 oz, and that includes an insulated hood. The ZenBivy Bed is worth noting here because even though the complete package is rather heavy (2 lbs, 10.2 oz), the quilt can be used and carried on its own, and it only weighs 1 lb 9.6 oz.
The heaviest product in this test is the synthetic Big Agnes Bolten (2 lbs, 15 oz), which justifies its weight by being a supremely comfortable model that does well in wet weather.
Compressibility
Compressibility is closely related to both warmth and weight because it is dependent on the quality of the insulation used. Down bags almost always compress into smaller bundles than synthetic bags, which is not the fault of the products but rather the nature of these insulations. We found this to be true, with the synthetic Big Agnes Bolten being the least compressible. However, the ZenBivy Bed, with its sheet, pillow, and multiple pieces, also ended up packing into quite a large package, even though the insulation is down. Most of the bags in this review could be compressed even smaller if packed into a compression sack with straps that cinch down the sides. Only some came with an included compression sack, while most came with a generic stuff sack and would require an after-market compression sack to be purchased.
Our 3-season sleeping bag line-up compressed into included sacks: Sea to Summit Flame III, Therm-a-Rest Vesper, ZPacks Classic Sleeping Bag, Patagonia 850, Feathered Friends Tanager, The North Face Hyper Cat, and the Big Agnes Bolten.
Predictably, the models that compressed the smallest were the ones with the highest quality down and fewest bulky features, like zippers and hoods, to take up space. The Feathered Friends Tanager, Therm-a-Rest Vesper, and Sea to Summit Flame took the highest scores for this metric with the ZPacks Classic just one point behind.
Warmth
Warmth is one of the most important features of a sleeping bag. If insulation wasn’t required, then a sleeping bag would not be used at all. Mostly, warmth is a subjective metric, but we back up our conclusions by evaluating EN (European Norm) temperature ratings whenever possible. We felt that the ZPacks Classic Sleeping bag was the warmest: it was the fullest and loftiest of all the bags in this test. Our research confirmed this assessment: ZPacks stuffs its baffles with 30% more down than the fill power dictates. This over-filling helps keep the bag warm and super-lofty even as loft loss occurs throughout its use.
The ZPacks Classic Sleeping Bag was the warmest 3-season bag we reviewed. We tested it on a 3-day ascent of El Cap. Here our testers prepare for a night on a porta-ledge.
The Feathered Friends Tanager, Sea to Summit Flame III, Therm-a-Rest Vesper, and Patagonia 850 all tied for second place in warmth. Each of these bags, including the ZPacks, is constructed with full box baffles rather than sewn-through seams. This method of construction is more expensive and complicated, but more durable and much warmer. A box baffle allows the insulation to reach its full loft height, rather than trapping and squishing it into a tapered, sewn-through baffle. It also eliminates the presence of any cold spots, because there are no seams that cold air can seep through. Instead, the bag’s occupant is fully encased in a consistent layer of insulation.
Ventilation
Since a 3-season sleeping bag’s claim to fame is that it can be used in the heat of summer as well as in cool shoulder seasons, ventilation features increase a bag’s comfort in warm weather. The hoodless quilts from ZPacks and Therm-a-Rest are extremely versatile in this regard. They can be folded back and left open to achieve airflow. The ZenBivy Bed is the standout product for this metric. With multiple pieces, it can be configured differently for a range of temperatures. The quilt can be left unattached to the sheet or even used entirely on its own, which makes for excellent ventilation.
The unique design of the ZenBivy Bed allows for excellent temperature regulation. If it is cold you can cinch the foot box and nestle underneath the hood. If it is warm you can sleep with the foot box open and the blanket tossed back. If it is really hot you can just use the quilt on its own.
The ones with the worst ventilation features were the ones with short zippers or no zippers at all. The Tanager is a fully enclosed tube with no zipper, so the only way to dump excess heat is to push the whole bag lower on your body. At least it does not have a hood. The North Face Hyper Cat has one half-length front center zipper, which does not leave much room for letting cool air inside. Even a standard mummy bag shape with a side-zipper, like on the Sea to Summit Flame, offers more ventilation than the front zip on the Hyper Cat.
Features
All of the bags in this review are kept simple in order to maintain a low weight. Simplicity is exactly what we look for in a top-tier product for backpacking. This means that there are no stash pockets or comforting extras on any of these products. The features that we evaluated are the overall design and shape of each bag. We tested four that employ the standard mummy shape, two with side zippers: The Sea to Summit Flame III and the Big Agnes Bolten, and two with center zippers: the Patagonia 850 and The North Face Hyper Cat. Two products were lightweight backpacking quilts: the ZPacks Classic Sleeping Bag and Therm-a-Rest Vesper. The Feathered Friends Tanager is in a class of its own as a hoodless, zipperless, tapered tube. And finally, there is the ZenBivy Bed, which is a multi-piece sleep system that imitates the comfort of a bed from home. The ZenBivy comes with a sheet that attaches to a sleeping mat, a quilt that can be zipped to the sheet or used independently, and an inflatable pillow with a super-soft case. The ZenBivy and the quilts offer freedom from the restrictive shape of a mummy bag and accommodate different sleep positions and lots of rolling around throughout the night.
The Therm-a-Rest Vesper is a lightweight backpacking quilt. One of its features is called Synergy Link. These are thin, stretchy straps that wrap along the underside of your sleeping mat to keep the bag tucked in around the pad and to keep the sleeper from rolling off in the middle of the night.
Durability
Short of tearing a hole in one of the sleeping bags, durability is an important metric that is difficult to assess. Zippers tend to be problem spots in insulated products like jackets and sleeping bags, so the models that do not have zippers are likely to last a little longer just by virtue of not being vulnerable to zipper failure.
Long-term, down bags have more longevity because the natural insulation can survive more compressions and expansions before getting worn out. A properly cared for down bag can last years. Synthetic insulation starts to wear out and lose loft much sooner.
Short-term, synthetic bags are more durable. If a hole is torn in the shell material, synthetic insulation, which is one big sheet inside the bag, will not leak out or get lost. Down, on the other hand, falls out and floats away, leaving you with an empty piece of delicate fabric that provides no warmth.
Most of the sleeping bags in this 3-season review are made from ultralight textiles ranging from 20-denier all the way down to 7-denier materials. The lower the denier, the more fragile it can be. Here is the Feathered Friends Tanager (right) and the Sea to Summit W’s Flame III.
To compare durability, we noted the denier of the textiles used as shell materials in each bag. Denier measures the linear density of fibers. A higher denier indicates more dense fibers over a given length. Denier can provide some indication of durability, but thread count and weave pattern also affect the sturdiness of a product, so a lower denier does not always signify lower durability. Typically, a high denier also equates to higher weight, so lightweight products feature low denier fabrics.
Many of the products in this test use impressively lightweight materials: the Patagonia 850 uses a 15-denier shell and liner materials, the Therm-a-Rest Vesper and Sea to Summit Flame use 10d shells, and the Feathered Friends Tanager features a 7-denier shell. Even these models with lightweight materials held up to the rigorous demands of testing. We did not experience any rips or tears.
Test Methods
Hours of product research and spec comparison will tell you a lot of things about different outdoor products, but all that nerding out will not tell you one key thing: how does the item actually perform when you use it? Is it comfortable? Is it warm? And even more subjectively, do you like it? At Gear Institute we believe in a combination of research and good-old-fashioned usage.
Sleeping bag testing during a High Sierra Summer.
We spent a lot of time building out spreadsheets and comparing details such as weight, down fill, and the denier of the textiles used in the shells and liners. We independently weighed each product on our own scale to verify the manufacturer weights and added this data to our notes. But we also spent multiple nights in each sleeping bag to reach the more subjective conclusion of which ones we like the best. For this 3-season sleeping bag review, we solicited opinions from eight different testers of different ages, genders, and experience levels to best understand how different people view and value different features. We stuffed and carried, unstuffed and slept, zipped and cinched each and every one multiple times. These bags took trips to the Wind River Range in Wyoming, the Bugaboos in Canada, Cochamo in Argentina, the High Sierra in California, and a couple even spent a few nights on a portaledge hanging on the side of El Capitan in Yosemite National Park.
Testing the ZPacks Classic Sleeping bag and the Feathered Friends Tanager on the side of El Cap.
What is a 3-Season Sleeping Bag?
We define a 3-season sleeping bag as one rated for between 15 and 29 degrees Fahrenheit. These bags will be most often used in the summer, but are warm enough for the cool shoulder seasons of spring and fall. This means that warmth is a high priority, but ventilation is still a consideration. If you were only going to purchase one sleeping bag, this would be the style we suggest because it is the most versatile for the widest range of conditions.
Insulation type:
In this test, we included bags featuring both insulation types.
Down
Down bags are insulated with feathers, often from geese but sometimes from ducks. Down is commonly considered the best insulation for lightweight products because it has the highest warmth-to-weight ratio of any insulation and can pack down very small. Down feathers are durable enough to handle years of expansions and compressions and still perform well. This insulation’s primary weakness is that when it gets wet, the feathers clump together and stop insulating, becoming useless. Many manufacturers now treat their down with a water resistant coating, such as the Nikwax Hydrophobic Down in the Therm-a-Rest Vesper, that will withstand light rain and moisture. Down products are vulnerable to tears since a breach in the shell material allows the feathers to leak out.
Synthetic
Synthetic insulation is composed of man-made fibers. Often, it tries to mimic the warmth-to weight ratio and high compressibility of down. There are many different brands of synthetic insulation on the market, and these insulations are improving with each new generation. Synthetic insulation’s primary benefit is that, unlike down, it maintains insulating properties when wet. A synthetic bag is the best choice if camping in a wet climate with frequent rain. Synthetic insulation wears out and loses its loft sooner than down, so a synthetic product does not have the longevity of a down product. In the short-term, it can seem more durable because rips and tears won’t compromise the function of the bag.
Design and Shape:
To make sleeping bags lighter and smaller, companies are experimenting with shapes other than the classic tapered mummy shape, such as quilts and bed-like systems. We included examples of all three of these styles in this test.
Classic mummy bags
A mummy bag has a tapered shape that is wider at the shoulders and narrower at the feet. (Though most women’s models break this mold and are wider in the hips and narrower at the shoulders.) This shape is an extremely efficient way to conserve heat and stay warm, while also resulting in a lightweight and packable product. Most mummy bags have a zipper down one side, a hood with a cinch, and a draft collar to seal in warmth around the neck and shoulders. Many modern users feel this shape is confining and uncomfortable, and companies have found ways to create bags that allow for more freedom and are lighter weight, but they compromise a little on lost warmth.
Backpacking Quilts
Backpacking quilts are the lightest weight option for sleeping in the backcountry. A backpacking quilt can be a flat blanket, like in the case of the Feathered Friends Flicker or in the separate quilt piece from the ZenBivy Bed. However, most often a backpacking quilt is a hoodless, backless, and zipperless bag with a fully enclosed foot box. The Therm-a-Rest Vesper is an excellent example of a backpacking quilt. There are variations on this design, such as the ZPacks Classic Sleeping bag, which is still a hoodless quilt with an enclosed footbox, but it has a zipper down the backside. The benefit to a quilt is that it strips away unnecessary parts of the sleeping bag, and leaves you with nothing but functional insulation. Bags of this style typically require some backcountry camping experience and may not be comfortable for beginner backpackers.
Bed Systems
The market response to complaints about restrictive mummy bags is the advent of bed-like sleep systems. Sierra Designs makes a product called the Backcountry Bed and the ZenBivy Bed is a new sleep system that was popular enough to make its start through a Kickstarter campaign. Bed systems do away with confining footboxes and typically have multiple pieces, one of them a blanket, and aim to resemble the freedom of sleeping underneath blankets in your bed at home. These systems will not be the most efficient in weight and packability, but they might be the most comfortable.
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