Hot sleeper? This guide from Comfort Protocol compares the three big options and shows when each one actually feels coolest.
Who wins for cooling?
- TENCEL™ lyocell (often sold as eucalyptus/lyocell) typically feels coolest in humid conditions thanks to higher moisture uptake and rapid moisture-vapor movement. See lyocell’s moisture behavior in textile references and overviews of lyocell moisture regain (~11%) and humidity sorption vs cotton.
- Cotton percale can feel crisper and airier because the weave breathes well; in dry or AC-cooled rooms with decent airflow, it can sleep just as cool—or cooler—than lyocell. See percale vs. sateen breathability and why sateen runs warmer.
- “Bamboo” sheets are almost always rayon/viscose made from bamboo; cooling varies by weave and weight, so don’t assume they’re greener or cooler by default. The FTC requires the “rayon (viscose) made from bamboo” label and has enforced it in multiple actions.
Quick comparison (cooling-relevant traits)
| Factor | Tencel (Lyocell) | Cotton (Percale) | “Bamboo” (Viscose/Rayon) |
|---|---|---|---|
| Base fiber | Regenerated cellulosic (wood pulp), branded TENCEL™ | Natural cellulosic (cotton) | Regenerated cellulosic from bamboo pulp |
| Typical moisture regain* | ~10–11% | ~7–8.5% | ~11% (viscose) |
| What that means | Absorbs vapor fast → feels less clammy in humidity | Great airflow; crisp feel in dry rooms | Can manage moisture, but feel varies widely by weave/weight |
| Best cooling weave | Plain/percale-like or light sateen | Percale (≈200–350 TC) | Percale/plain if available; avoid heavy sateens if you run hot |
| Eco/process note | Lyocell made by Lenzing uses a closed-loop process recovering ~99.8% solvent | Look for organic/OEKO-TEX | FTC: label and market accurately as rayon/viscose |
| Feel | Silky-cool, drapey, low cling | Crisp, matte, airy | Silky/drapey; can cling if dense/sateen |
| Best for | Humid climates, night sweats | Dry/temperate rooms, AC + fan | Depends on construction; vet specs |
*Moisture regain sources: lyocell ≈11%; cotton ≈7–8.5%; viscose ≈11%.
The science of “cool”
“Cooling” blends air permeability (air passes through the fabric) with moisture management (how quickly vapor/sweat moves away from skin).
- Weave matters: Percale’s one-over/one-under weave is typically more breathable than sateen’s longer floats, which trap more warmth.
- Fiber matters too: Lyocell’s higher hygroscopicity helps in humidity; studies show lyocell retains more moisture at the same RH than cotton, minimizing that sticky feel.
Bottom line: Weave + weight + fiber determine cooling. If you’re hot, start with percale; if you’re sweaty/humid, lyocell shines.
Material deep-dives
Tencel (Lyocell)
- Why it sleeps cool: Lyocell’s moisture regain is ~11% and it handles vapor quickly, which helps prevent clamminess in humidity.
- Eco/process: Lenzing’s lyocell is produced in a closed-loop system recovering ~99.8% of the solvent (N-MMO).
- Feels like: Smooth, drapey, often “cool-to-the-touch.”
- Watch-outs: Heavy, very dense sateens can feel warmer; choose lighter constructions.
Cotton
- Why it sleeps cool: In a percale weave (200–350 TC), cotton breathes exceptionally well and feels crisp/airy—especially in dry or AC-cooled rooms.
- Moisture regain: Common references list ~7–8.5% for cotton.
- Watch-outs: Dense sateens (very high thread counts) tend to run warmer; ultra-high “thread count” often means multi-ply marketing, not better cooling.
“Bamboo” (Rayon/Viscose made from bamboo)
- Labeling reality: Per the FTC, most “bamboo” bedding must be labeled “rayon (or viscose) made from bamboo.”
- Cooling: Viscose is hygroscopic like lyocell (≈11% MR), but feel depends heavily on weave and fabric weight.
- Eco note: Conventional viscose uses harsher chemicals; that’s why the FTC polices “bamboo” marketing (examples of enforcement). Prefer transparent disclosures and certifications.
Weave matters more than the label
If you do nothing else, choose percale (≈200–350 “true” thread count) over sateen for cooling—percale is usually more breathable, while sateen tends to retain more heat. Pick lighter GSM fabrics for the airiest feel.
Certifications worth checking
- OEKO-TEX® STANDARD 100 — independent testing that the textile is free from harmful substances; widely used baseline. (See their overview).
- TENCEL™ branding — confirms you’re getting Lenzing lyocell made via the closed-loop process.
Cooling decision tree
- Wake up damp / live in humidity?
→ TENCEL™ lyocell in a breathable weave. See lyocell moisture dynamics. - Room is dry / good airflow (fan + AC)?
→ Cotton percale (≈200–350 TC). See why percale is airier. - Curious about “bamboo”?
→ Verify the label (FTC guidance). Choose lighter percale/plain weaves if you run hot.
How to read a product page (so you don’t get bamboozled)
- Fiber: Look for “TENCEL™ lyocell,” “100% cotton,” or “rayon/viscose made from bamboo.” If it just says “bamboo,” the FTC requires clearer labeling.
- Weave: Prefer percale for cooling; be cautious with dense sateen if you’re a hot sleeper (why).
- Thread count: Ignore sky-high numbers; 200–350 percale or 300–400 light sateen is a good range (overview).
- Certification: STANDARD 100 by OEKO-TEX® is a solid baseline.
- Weight (GSM): Lower GSM = lighter and usually more breathable.
Care tips that keep sheets cooler longer
- Skip fabric softeners: they coat fibers and reduce moisture transport.
- Cool wash, low heat dry to protect fiber structure.
- Don’t over-dry—remove slightly damp (cotton percale stays crisper).
- Rotate sets so surfaces don’t polish into a clingier feel.
FAQs
Is Tencel really cooler than cotton?
In humid environments or if you sweat, many sleepers perceive lyocell as cooler because it absorbs/releases moisture rapidly and outperforms cotton at the same humidity in lab comparisons. In dry, breezy rooms, a cotton percale weave can feel equally or more cooling thanks to airflow.
Are bamboo sheets the coolest?
Not automatically. Most “bamboo” sheets are rayon/viscose; cooling depends on weave and weight, not the bamboo buzzword.
What thread count is best for cooling?
For cotton percale, ~200–350 usually breathes best. Dense, very high counts can trap heat.
What certifications matter?
OEKO-TEX® STANDARD 100 checks for harmful substances; TENCEL™ branding indicates Lenzing’s closed-loop lyocell process with ~99.8% solvent recovery.
Is “bamboo” more eco-friendly?
Not necessarily. Traditional viscose uses harsher chemicals; that’s why the FTC watches the claims closely. Lyocell uses a different, closed-loop solvent system.
Conclusion
If humidity and sweat are your main issues, TENCEL™ lyocell is the safest bet. If you sleep in a dry, well-ventilated room, cotton percale offers unmatched crisp, airy cool. “Bamboo” viscose can be comfortable, but focus on weave, weight, and honest labels. Pair your sheets with a breathable mattress protector and a fan for the biggest cooling gains.
