Sleeping hot? What a mattress can (and can’t) do about it

The short answer: The heat comes from you; a mattress decides how easily it gets away. Spring units and latex let air move, while thick memory foam moulded closely around the body holds warmth in. So if you sleep hot, a pocket-spring hybrid or a latex comfort layer is the safer starting point, and a softer mattress you sink deep into will feel warmer than a firmer one. Gel, copper and phase-change “cooling” features are real but their effect is not published in any comparable way. Your sheets, quilt, protector and bedroom often matter as much as the mattress.

Where the heat goes

Your body sheds heat through the night, and more of it in the early part of sleep. Whatever you lie on and under either lets that heat move away or holds it next to you. A mattress affects it in three ways: how much material is in contact with your body, whether air can move through it, and how readily the surface itself absorbs and holds warmth.

Construction matters most

• Pocket-spring hybrids. The spring core is mostly air, and air moving through it carries heat away. The comfort layers on top decide how much of that you feel: a thin latex layer sleeps cooler than a thick memory foam one.
• Latex. Naturally open-celled and springy, so you rest on it rather than in it. It generally sleeps cooler than memory foam. See latex explained.
• All-foam. Dense foam, and memory foam in particular, moulds closely around you and holds warmth. Thick memory foam layers are the most common source of complaints about heat.
• Innerspring. Breathes well, with a thin comfort layer, so heat is rarely the issue — movement and pressure are.

Firmness plays a part too. The deeper you sink, the more of your body is surrounded by material. A softer mattress of the same construction will usually feel warmer than a firmer one.

Our hybrid vs memory foam guide compares the two most common constructions in full.

Cooling features, honestly

Mattress makers have several ways of tackling foam’s heat:

• Gel-infused foam — gel beads or swirls in the foam, meant to absorb heat.
• Copper or graphite particles — added to foam to conduct heat away from the body.
• Open-cell and perforated foams — structured to let more air through.
• Phase-change materials — usually in the cover, designed to feel cool to the touch by absorbing heat as they warm.

These are real materials. What brands do not publish is how much difference they make, measured in a way you could compare between mattresses. A cool-to-the-touch cover can feel great in the first minutes and matter less by 3am, once the surface has warmed up. Treat cooling features as a bonus, and choose the construction first.

Covers and protectors

The cover is the only part of the mattress your skin meets through the sheet. Breathable knitted covers made from cotton, wool or cellulose fibres generally feel cooler than heavy synthetic ones.

The protector is a common hidden culprit. Older vinyl-backed waterproof protectors trap heat and moisture. A protector with a thin breathable membrane under a cotton or wool surface keeps the mattress protected without most of the warmth. Our protector guide explains the types.

Bedding

• Sheets. Cotton percale — a plain, crisp weave — and linen tend to feel coolest. Sateen weaves are smoother but a little warmer. Polyester and microfibre sheets breathe less.
• Quilts. A lighter quilt for summer makes a big difference. Wool is good at managing moisture, which helps if you sweat at night. If you share a bed and one of you runs hot, two separate quilts of different weights are a simple fix.
• Pillows. Dense memory foam pillows hold heat around the head and neck; latex or fibre fills are often cooler.

The bedroom

• Keep air moving. A ceiling or pedestal fan is one of the most effective changes you can make.
• Block daytime heat. Closing blinds or curtains on hot days keeps the room from heating up before night.
• Cool down before bed. A lukewarm shower, and avoiding heavy exercise or a big meal late in the evening, help your body start to cool.
• Air conditioning, if you have it, set to a comfortable temperature rather than very cold, with a light layer of bedding.

If night sweats are new

If you have started waking drenched in sweat, especially without an obvious reason such as a hot night or heavy bedding, see your GP. New night sweats can have medical causes, including medications, hormonal changes and infections, which a mattress will not fix.

Where to go from here

Our best mattresses for hot sleepers page lists specific models, built from what makers publish about their construction and materials.

Common questions

What type of mattress sleeps coolest?
Generally, pocket-spring hybrids with thin comfort layers, and latex. Thick memory foam tends to sleep warmest.

Do cooling mattresses actually work?
The construction makes a real difference; individual cooling additives are harder to judge, because their effect is not published in a comparable way.

Is memory foam always hot?
Not always, but it is the material most associated with heat, particularly in thick layers and softer mattresses.

Can a mattress protector make me hot?
Yes, especially older vinyl-backed waterproof ones. A breathable membrane under a cotton or wool surface keeps most of the protection without the heat.