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REI Co-op Joule 21 Review

The Joule is a great lightweight, quality choice for all your backpacking adventures.
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Price:  $299 List | $299.00 at REI
Pros:  Warm, high-quality materials, good price
Cons:  Uncomfortable fit, zipper fabric bulky and uncomfortable
Manufacturer:   REI
By Jessica Haist ⋅ Review Editor  ⋅  Oct 9, 2018
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#5 of 15
  • Warmth - 25% 9
  • Weight - 25% 8
  • Comfort - 20% 8
  • Packed Size - 15% 8
  • Features - 15% 8

The Skinny

The REI Co-op Joule 21 is a high scorer in our review and directly competes with bags like the Rab Neutrino 400. It's heavier than the Neutrino but also warmer and much less expensive. It kept us warm and cozy on cold, wet, and windy nights in the High Sierra. The 700 fill-power down insulation provides a good night's sleep in the backcountry, and we appreciated its low weight-to-warmth ratio. We think the Joule is a great choice for any backpacking need at a great price.

Compare to Similar Products

Our Analysis and Test Results

A high-quality bag that's warm and relatively light, the Joule was a pleasant surprise to our testers.

Performance Comparison


After the Feathered Friends Egret UL 20 - Women's, we think this contender is one of the warmest sleeping bags in this review and is just a little warmer than the Mountain Hardwear Heratio that is rated to 15 degrees. We feel that its EN rating of 21°F is dead on, and indeed, it kept us warm down to that temperature. The bag feels cozy, and the 700 fill down is very lofty. The Joule's shell material protected our testers from wind when they slept out under the stars on windy nights.

The bag's shell material has a waterproof coating. This is an added piece of mind when we were in a torrential downpour in a floorless shelter. It kept us dry throughout the night despite a constant misting from water bouncing off of the ground and tarp. This could be a good option for someone who wants a down bag in a wet climate like the North Cascades.


The Joule 21 weighs in at 2.19 pounds, which is not super lightweight for a down sleeping bag but falls in after our top 4 super light sleeping bags in this review. This is a pretty average weight for a down backpacking sleeping bag, but we think it could be lighter.


Thankfully, REI has abandoned the woman's hour-glass shape and made the leg area larger. This is an upgrade. The proportions were previously about as exaggerated as Barbie's. Now the bag is much more comfortable, and the dimensions are similar to the Heratio and Neutrino.

Packed Size

The stuff sack that is included with the Joule is not a compression sack but is made from lightweight materials. When we took it out in the backcountry, we used one of our own compression sacks instead, and it packs down quite small. We really like the compression sack that comes with the Rab Neutrino 400 - Women's.


REI has trimmed the fat in this department, and we are in favor of the work they have done. They have gotten rid of the stash pocket entirely and added a light colored liner fabric so you can find your missing sock without difficulty. The color hides dirt. The zipper works well, contrary to reports we read about this bag and so we are wondering what's with the super burly zipper lining fabric? We think it may be a reaction to complaints of zipper catching on this bag, but unfortunately, it adds weight and bulk, and our testers can feel it when they're sleeping; it bunches and creates a hard, uncomfortable lump.

Although the waterproof coating on this bag works well, it also adds extra weight. We appreciate the degree of mental comfort it gave us when using it in an exceptionally wet summer season in the Sierra. We watched water bead off the coating with relief more than once in our floorless shelter, but we wonder how long this coating will last without being re-treated.

Best Application

Overnight to week-long backpacking trips are what this bag was made for. For truly long-distance thru-hiking, we would opt for an even more lightweight model. But for the majority of folks heading on backpacking trips, the Joule 21 is ideal.


The Joule is a great value for your money and we agree that it is worth it to invest in a quality down bag like this model. If you're looking for a really lightweight bag the Sierra Designs Women's Cloud 800 costs the same and is much lighter.


The REI Co-op Joule 21 is warm and relatively lightweight. If it weren't for the lower fill power weight, this bag would be neck and neck with the Rab Neutrino. We still think it would be a great choice for your backpacking adventures.

Jessica Haist