Tencel, bamboo or cotton: which mattress cover is best if you sleep hot
The mattress cover gets one line on the spec sheet and it is the only layer you actually touch. Most are polyester knits, sometimes with a cool-touch finish, quilted to a layer of polyester wadding. If you sleep hot, the cover fibre and how it is made matter as much as what is under it.
The three fibres
Tencel is the brand name for lyocell, a fibre made from wood pulp (usually eucalyptus) in a closed-loop process. It is smooth, cool to touch, and excellent at moving moisture away from the skin and releasing it. It dries quickly. It is the fibre of choice for hot sleepers and night sweats.
Bamboo on a mattress cover almost always means bamboo viscose (rayon): bamboo pulp dissolved and spun into fibre. It is soft and cool and wicks well, close to Tencel in feel. The "bamboo" part is a starting material; the process is chemical, and the eco claims that come with it are usually overstated. As a fabric it is fine.
Cotton is cotton. Breathable, absorbs moisture rather than moving it, dries more slowly than Tencel, feels natural and crisp. Percale cotton sheets are cool; a cotton mattress cover is good but not the best for sweat.
Polyester, the one nobody advertises, is what most covers are. It does not absorb or move moisture. It feels cool at first touch if it has been treated, and holds heat and sweat after that.
The comparison
| Tencel (lyocell) | Bamboo viscose | Cotton | Polyester | |
|---|---|---|---|---|
| Cool to touch | Yes | Yes | Slightly | Only with a finish, briefly |
| Moves sweat away | Best | Good | Absorbs, slow to dry | No |
| Dries | Fast | Fast | Slow | Fast but holds smell |
| Feel | Silky, smooth | Soft, slightly slippery | Crisp, natural | Synthetic |
| Durability | Good | Fair | Good | Good |
| Cost | Higher | Middle | Middle | Low |
For a hot sleeper: Tencel first, bamboo viscose second, cotton third, polyester avoided.
Quilted or unquilted matters more than the fibre
A cover quilted to 2 to 3 cm of polyester wadding is a jumper on top of the mattress, whatever fibre it is made of. Wadding traps heat and blocks whatever cooling the layer beneath could give. An unquilted or lightly quilted cover puts you almost directly on the comfort layer, which is where latex or wool or graphite foam can actually do something.
So the two questions are: what is the cover fibre, and what is quilted into it. A Tencel cover quilted to thick polyester is worse for heat than a thin cotton knit with nothing under it.
Finishes: phase-change and cool-touch
A phase-change finish (PCM) is a real thing: microcapsules that absorb heat as they melt and release it as they set, buffering the surface temperature for the first hour or so. Useful, especially for getting to sleep. A cool-touch finish is a fibre treatment that feels cold to the hand and does nothing once you are lying on it. Read the difference.
Do not undo it with the protector
A plastic-backed waterproof protector on top of a Tencel cover turns it back into polyester. If you need waterproofing, use a Tencel or cotton protector with a breathable membrane. If you do not, use a plain cotton or Tencel protector.
How we specify ours
Most of our chapters use a knitted stretch cover, lightly quilted, because it is breathable and it moves with the comfort layer. The Hot Flush uses an unquilted Tencel cover with a phase-change finish, so there is nothing between you and the latex. The Hotel Bed uses damask, a woven cotton-rich cover, over natural fibres.
The short version
- Tencel moves sweat best; bamboo viscose is close; cotton is good; polyester is the problem.
- Unquilted beats quilted for heat, whatever the fibre.
- Phase-change finishes work for the first hour; cool-touch finishes work for a second.
- A plastic protector cancels all of it.
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