The Slumber Cloud UltraCool Pillow puts Outlast phase-change fabric, the material Slumber Cloud built its bedding line on, into a soft down-alternative pillow. Apartment Therapy rated the adjustable version 4.5 out of 5, and Sleepopolis, reviewing the same Outlast fabric in Slumber Cloud's Nacreous cover, called it quite breathable and credited it with limiting heat retention overnight. The 30-night trial is the shortest here.
Full review
Outlast phase-change fabric, not a cool-touch coating
The cooling comes from Outlast, a phase-change material that absorbs body heat into microcapsules in the fabric when you warm up and releases it back when you cool down. Slumber Cloud claims it cuts heat buildup by up to 50 percent against a standard polyester pillow.
The distinction from a passive material like cotton or bamboo is that it works in both directions. That matters in the middle of the night, when body temperature drops and a purely cold surface starts to feel unpleasant rather than helpful.
Sleepopolis on the same Outlast fabric
Sleepopolis, testing the Slumber Cloud Nacreous cover that uses the identical Outlast treatment, called it quite breathable and credited it with limiting heat retention through the night, which is the clearest independent read on the fabric itself.
Apartment Therapy, rating the adjustable UltraCool 4.5 out of 5, describes it as staying neutral rather than turning cold, which is the behaviour owners of phase-change bedding tend to report.
A soft, down-alternative feel rather than foam
Despite the technical cover, this is a plush pillow. The fill is 100 percent polyester fiberfill, so it has the lightweight moldability of a traditional fluff pillow rather than the dense conforming feel of memory foam.
The knit cover is cool on contact without feeling slick or plastic-y, and it drapes rather than crinkles, so the pillow reads as hotel bedding rather than as a sports-cooling product.
Two inserts that change the firmness profile
The Adjustable model uses two removable inserts, one fiberfill and one memory foam. Pulling the foam insert leaves a soft, all-fluff pillow; leaving both in produces a denser feel that holds shape better through a night on your side.
The standard model ships at a fixed loft in Soft/Medium and Medium/Firm. Sizes run Standard 20x26, King 20x36 and a 48-inch body pillow, with Soft/Medium generally suiting back and stomach sleepers and Medium/Firm side sleepers.
Cover and fill both go in the machine
The whole pillow washes cold on gentle and tumble dries low, which is unusual in this category, where most phase-change and gel pillows carry a cover-only wash spec.
The Outlast treatment is applied to the fibers rather than laminated on as a layer, so it does not wear off the way a surface coating does, and the polyester construction dries faster than down or latex would.
A 30-night trial, against 365 from Saatva
The trial window is the weakest part of the offer. Thirty nights is the shortest in this lineup by a wide margin, where the Saatva Latex Pillow runs 365 and the Coop Cool+ 100, which is short for a pillow at this price.
The cooling also works best against skin. A thick cotton percale case noticeably blunts the effect, so a thinner Tencel or bamboo viscose case is the better pairing, and a humid bedroom suits latex or silk fill better than polyester.
Strengths
- +Outlast phase-change fabric absorbs and releases heat rather than just feeling cool at first touch
- +Two firmness options and three sizes, including a 48-inch body pillow
- +OEKO-TEX STANDARD 100 certified, with cover and fill both machine washable
- +The Adjustable model's two-insert system changes the firmness profile substantially
- +Outlast treatment is worked into the fibers rather than laminated on top
Watch-outs
- −The initial cool-touch sensation fades as the phase-change material saturates
- −A 30-night trial is the shortest in this lineup
- −Cooling is noticeably blunted by a thick pillowcase
- −Polyester fiberfill feels less breathable than latex or silk in a humid room
How it compares
It trades the adjustable loft of the Coop Cool+ for the Outlast fabric, which is the more proven temperature-regulating material in this category. It cools harder on contact than the Saatva Latex Pillow, though the Saatva's airflow story is more consistent in a hot bedroom, and it is roughly level with the Purple Harmony on temperature while feeling much softer.
Rating sources
“The integration of the Outlast Technology helps to limit heat retention and is quite breathable.”
“The pillow felt like I was sleeping on the cool side of it all night and I definitely had no issues with sleep.”
“Why I Love Slumber Cloud's Adjustable UltraCool Pillow — Outlast's NASA-developed technology actively regulates temperature to keep you cool all night.”
Our 4.5 score is the average of these published ratings. Ratings marked * were derived from the reviewer’s written analysis or video transcript — the publisher didn’t print an explicit numeric score, so we inferred one from their own words. Click through to verify. More about methodology.
