The NEMO Kayu 15 is a down-insulated mummy sleeping bag designed for three-season backpacking and camping. Weighing 2 lbs 3 oz, the Kayu is not the lightest weight sleeping bag in its class, but it has several features that differentiate it from comparable sleeping bags with the same temperature rating. Chief amongst these are special thermo-regulation gills on the chest that let you vent it in warmer weather without having to crack open the side zipper and let in chilling drafts. It also has waterproof/breathable fabric on the hood and footbox to prevent tent condensation from degrading the bag’s insulation, since these are the parts of the sleeping bag most likely to be affected.
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Specs at a Glance
- Gender: Men’s
- Tested Lower Limit: 17F / -8C
- Tested Comfort Limit: 27F /-3C
- Insulation: 800 fill power
- Water-Resistant Down: Yes
- Weight: 2 lbs 3 oz / 992g (Actual weight is 2 lbs 4 oz)
- Down Fill Weight: 17 oz / 480 g
- Length: 72 inches tested (78″ also available)
- Girth: Shoulder (63″), Hip (55″), Footbox (46″)
- Compressed Volume: 5.9L
- Compression Sack Weight: 3.3 oz (included)
- Storage Bag: Included
- Fabric: 20D nylon ripstop with DWR on the shell, 30D nylon taffeta lining, and a 40D nylon ripstop waterproof/breathable footbox.
Sleeping Bag Features
Unlike NEMO’s spoon-shaped bags which are designed for side sleepers, the Kayu is primarily designed for back sleepers who don’t roll onto their sides or curl up when they sleep. To that end, the bag is cut somewhat slim in the chest, although roomier in the hips and foot box, to reduce the amount of body heat required to heat it up and keep it warm while you sleep.
Feature-wise, Kayu 15 (also available in a 30-degree model) has all of the standard features you’d expect on a premium sleeping bag, including:
- a beefy draft collar that covers the upper chest and back to prevent heat from coming out the top when you move around inside the bag
- a 3/4 length, bi-directional zipper to save weight, but allow flexible venting of the legs independent of the chest
- a two-way side zipper with a draft tube and taped zipper stiffeners. The draft tube prevents cold air from leaking in between the zipper teeth while the stiffeners reduce the chance of a zipper snag and ripping the interior fabric.
- a jacket-style insulated hood, which turns with you if you roll over on your side at night
- an external zippered stash pocket to hold a headlamp at night
But the thing that really sets the Kayi apart of the therm-gills on its chest, which are zippered down baffles, that when opened release heat trapped inside the bag to cool you off. They’re the equivalent of pit-zips on a rain jacket although the back of the thermo-gill is not open but covered with a thin piece of nylon. Still, when the thermo-gills are unzipped, some of your core warmth is released through them. When they’re zippered closed, the insulated sides of the thermo-gill fill in the space under the zipper, trapping your core warmth once again.
But the real value of these Thermo-gills is that they increase the effective temperature range that the Kayu 15 can be used in by about 25-30 degrees, so you can use the same sleeping bag from 15F up to 40F, without having to buy a second warmer weather sleeping bag. That’s a big deal when sleeping bags cost a couple of hundred dollars.
Waterproof hood and footbox
The Kayu 15 has waterproof fabric on the foot box and the back of the hood to prevent tent condensation from compromising the insulation. This is a neat feature that makes a lot of sense on multi-day trips in the spring and late autumn when tent condensation is most likely to occur and will have the greatest impact on bag performance.
Comparable Down Sleeping Bags
|Make / Model||Type||Weight|
|REI Magma 15||Men's, Women's||28.2 oz / 799g|
|Western Mountaineering Versalite 10||Unisex||32 oz / 907g|
|Sea-to-Summit Ascent AcII 15||Unisex||39 oz / 1106g|
|Mountain Hardwear Phantom 15||Unisex||31.8 oz / 902g|
|NEMO Disco 15||Men's, Women's||43 oz / 1219g|
|Sea-to-Summit Flame 15||Women's||31.4 oz / 890g|
|Feathered Friends Flicker UL 20||Unisex||25.2 oz / 714g|
|Feathered Friends Egret UL 20||Women's||27.2 oz / 771g|
|Enlightened Equipment Convert 20||Unisex||26.5 oz / 748g|
|REI Magma Quilt 30||Unisex||19 oz / 539g|
The NEMO Kayu 15 is a down-insulated sleeping bag that has a much wider temperature range than its name would suggest. While it is designed to keep you warm in 15-degree weather, it has a temperature regulation feature called Therm-Gills that let you vent warmth up to about 40 degrees. That offers a degree of flexibility that is rare in a mummy sleeping bag.
Despite that, I’m on the fence about this bag. The Thermo-Gills are a nice feature to have and they worked for me, they’re just not as compelling a feature on the Kayu 15 as on a cold weather bag like the NEMO Sonic -20 or even the Sonic 0 where cracking open the side zipper isn’t a very comfortable alternative. That said that Kayu 15 is a perfectly decent 15-degree mummy sleeping bag and a viable option if you want to spend less than a more expensive and lighter-weight sleeping bag for the same temperature range.
Disclosure: NEMO donated a sleeping bag for review.SectionHiker is reader-supported. We only make money if you purchase a product through our affiliate links. Help us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.