How to Stay Cool at Night: Cooling Pyjamas and Sheets for Hot Sleepers

If you kick the duvet off at 3am, the fabric is usually doing more of the work than the room is. Two things decide how a cloth behaves: how freely air passes through it, and what the fibre does with water. Everything else — thread count, price, the word "cooling" on a label — follows from those two, or is decoration.

This is the full comparison: the fibre, the build and the published spec of every fabric we sell, sleepwear and bedding together, because the bed is a system and changing only the pyjamas often changes nothing.

The two properties that matter

Air permeability is how easily air moves through the cloth. It is set by the weave or knit, not by the fibre: an open plain weave breathes; a dense sateen at the same fibre and weight does not.

Moisture regain is how much water the fibre itself will hold at normal room conditions, measured as a percentage of its dry weight. The standard figures are worth knowing because they explain almost everything people notice in bed:

• Polyester — about 0.4%. Effectively none. Water has to sit on the surface, and under a duvet there is nothing to move it.
• Cotton — about 8.5%. Absorbs well, releases slowly. A damp cotton shirt stays damp.
• Silk — about 11%. Absorbs more than cotton and feels dry at a higher load.
• Modal — about 11 to 12.5%. The highest of the fibres we use, and it releases readily rather than holding on.
• Linen (flax) — about 12%. High regain and the most open weave of the four bedding cloths, which is why it is the warm-room recommendation.

One honest caveat: regain measures capacity, not speed. A fibre that holds a lot of water is not automatically the one that gets rid of it quickest — that depends on the yarn, the build and the air around it. Which is why the table below carries the build as well as the fibre.

Every fabric we sell, side by side

Fabric	Fibre	Spec	Build	Air and water
Modal Cloud (sleepwear)	95% modal, 5% elastane	Not quoted by weight	Fine knit, light and drapey	Highest regain of anything we use; releases moisture readily. The all-rounder.
Mulberry silk (sleepwear)	100% mulberry silk, Grade 6A	19 and 22 momme	Smooth woven filament	Cool on first contact because the surface conducts heat away quickly; high regain. 19 momme over 22 in a warm room.
Cotton (sleepwear)	100% cotton	Not quoted by weight	Woven, lightweight	Breathes well, absorbs well, dries slowly. Fine for a moderate sleeper, heavy by the small hours for a warm one.
Linen (bedding)	100% French flax, stonewashed	170 GSM	Single-layer plain weave, thick irregular yarn	The most open weave and the highest regain. The best bedding choice for a warm bedroom.
Cloud Cotton (bedding)	100% long-staple cotton	200 TC, double layer	Two fine gauze layers joined on a grid	Open weave, and the trapped air cuts both ways — airy in summer, insulating in winter.
Plain Cotton (bedding)	100% long-staple cotton	200 TC, single layer	Percale, plain weave	Crisp and cool to the touch, moderate airflow. The hotel feel.
Silky Cotton (bedding)	100% long-staple cotton	300 TC	Sateen, dense	The least airy of the four by construction. Bought for smoothness, not for a warm room.

The units are not interchangeable and that is not evasion — thread count suits cotton, GSM suits linen, momme suits silk, and knits are not honestly measured by any of them. Thread count, GSM and momme explains why, and which numbers are inflated elsewhere.

Which sleepwear fabric is the most breathable?

Modal, for most people, most of the year. It has the highest moisture regain of the fibres we use, it releases that moisture readily rather than holding it, and the fibre is fine enough that the knit stays light instead of bulky — so there is less insulation against you to begin with.

Silk is the close second and wins on first contact: it feels immediately cool because a smooth filament surface conducts heat away from the skin quickly. The trade-off is care. Silk is a hand-wash or delicate-cycle fabric, which is a real commitment if you are washing sleepwear twice a week in July. If you want the feel and will do the washing, a 19 momme short set is the version that makes sense in a warm room — lighter than 22, and the difference is noticeable.

Are cotton or modal pyjamas cooler?

Modal, and the gap is about drying rather than breathing. Cotton and modal both let air through and both absorb readily, but cotton at around 8.5% regain gives that water up slowly, so a cotton set that gets damp stays damp; modal at 11 to 12.5% releases it faster, so the surface next to the skin returns to dry.

Cotton is not a bad answer — our pure cotton sets are lovely and they breathe properly. They are the second choice here, not the first, and the honest version of the recommendation is: cotton if you run moderately warm, modal if you run genuinely hot.

Why does polyester sleepwear feel clammy?

Polyester is hydrophobic. At roughly 0.4% regain the fibre absorbs essentially nothing, so any moisture has to sit on the surface and evaporate. In activewear that works, because the knit is engineered to spread water out, you are moving, and there is air. In bed none of those conditions hold: you are still, you are under a duvet, and airflow is close to zero.

So a cheap polyester set does not wick anything anywhere. It holds a film of moisture between the fabric and the skin, which is the clammy feeling that wakes people up, and it is why so many people conclude they sleep hot when they are really sleeping in the wrong fibre. Read the composition label before the price: anything over about 20% polyester is worth avoiding for sleepwear, whatever the marketing says about wicking.

What are the best sheets for a hot sleeper?

Linen first, then double-layer cotton gauze. Linen has the most open weave of the four bedding cloths we sell and the highest moisture regain, and at 170 GSM it drapes rather than clinging. Cloud Cotton comes next: the weave is open, though the air trapped between its two layers insulates as well as ventilates, so it is the all-season choice rather than the coolest one.

Avoid a dense sateen if the room is warm. Silky Cotton is the smoothest cotton we sell and the least airy by construction — it is bought for the hand, and there is nothing wrong with that, but it is not the cooling choice. A 200 thread count percale sits in between: crisp, cool to the touch, moderately open.

We have put the lighter percale and linen options together on one page: bedding for hot sleepers.

Cut matters as much as fabric

• Short beats long for anyone who runs hot, and by more than you would think — bare forearms and lower legs simply have less cloth over them.
• Loose beats fitted. A relaxed set holds a thin layer of moving air; a clingy one does not. This is also why sizing up is a genuine strategy rather than a compromise.
• Buttons beat pullovers. A button-down top can be opened at the neck in the middle of the night without getting out of bed or fully waking up.
• Skip elasticated cuffs. A tight cuff seals the sleeve, so the air inside it stops moving.

What to change, and in what order

Sleepwear is one layer of three, and people almost always change it first and the duvet last. The duvet is usually the biggest single variable in the bed.

1. The duvet. Dropping the tog for summer does more than any fabric swap. A lower-tog summer duvet is the cheapest fix on this list; ours is a 10.5 tog all-season insert.
2. The sheet and cover. Linen if the room is warm, Cloud Cotton if you want one set for the whole year.
3. The sleepwear. A modal short set, sized generously, buttons at the front, no tight cuffs.
4. Nothing with a high polyester content, at any of the three layers.

You can build a bedding set and choose the fabric piece by piece — a linen fitted sheet under a gauze duvet cover is a perfectly sensible combination, and the builder prices the whole bed as one bundle. For sleepwear, start with the short pyjama sets, or read the pyjama fabric guide if you want the three sleepwear fabrics compared before you choose.

One thing we will not tell you: that any cloth we sell regulates your temperature, solves a symptom or improves your sleep. Fabric is fibre, build and weight, and what it does with air and water is the whole of what we can honestly describe.