Copper, Gel and Phase Change: What Mattress Cooling Technology Actually Does
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“Cooling” is the most heavily marketed word in the US mattress industry and the least precisely defined. Almost every brand claims it. Very few explain the mechanism, and the mechanisms are genuinely different from one another — some move heat, some absorb it, some simply let air through. Understanding which one you are being sold is the difference between a mattress that helps and a marketing sticker.
This guide explains the four approaches actually used in mattresses sold in the United States, what each one can and cannot do, and how to read a spec sheet without being misled.
First, why mattresses sleep hot at all
A sleeping adult gives off heat continuously. On a breathable surface that heat disperses into the air. The problem with memory foam specifically is twofold: it is a good insulator, and it is designed to conform closely to the body, which reduces the surface area available for air to move across. Heat accumulates in the pocket your body has made.
This is why the cooling conversation is dominated by foam mattresses. A traditional innerspring with an open coil layer has a large air cavity underneath the sleeper and rarely has the same problem. Every cooling technology below is, in effect, an attempt to give foam some of the airflow that springs get for free.
The four mechanisms, and what each one really does
| Approach | How it works | Realistic effect | Watch out for |
|---|---|---|---|
| Conductive infusion (copper, graphite, carbon) | A thermally conductive material is mixed into the foam so heat moves sideways and away from the contact point instead of pooling | Genuine but modest; helps most in the first hour, when the temperature difference is greatest | Conductivity moves heat, it does not remove it from the room. Effect diminishes once the whole layer warms up |
| Gel infusion or gel beads | Gel has a higher heat capacity than foam, so it absorbs more heat before its own temperature rises | Delays the point at which the surface feels warm | A finite buffer. Once saturated, gel offers no further benefit until it cools |
| Phase change material (PCM) | A substance engineered to change state at close to skin temperature, absorbing heat as it does so and releasing it as it cools | The most technically interesting; can regulate in both directions across a night | Usually a thin layer in the cover, so contact matters. Thick bedding over the top blunts it |
| Open-cell structure and airflow | The foam itself is manufactured with interconnected cells, or perforated, so air can move through the layer | Unglamorous but effective, and it does not wear out | Only works if the layers above it and the mattress protector are also breathable |
Conductive infusion: the copper approach
Copper is the most visible conductive infusion in the US market. Layla builds its memory foam mattress around copper-infused foam, and the reasoning is sound physics: copper conducts heat far better than polyurethane foam, so heat arriving at the surface spreads laterally instead of sitting under your shoulder.
Copper is also naturally anti-microbial. That is a real property of the metal, not an applied treatment, and it does not wash out. It is worth separating from the cooling claim though — they are two different benefits that happen to come from the same material.
What conductive infusion cannot do is make a bed cold. Heat moved sideways still has to leave the mattress eventually, and it leaves into your bedroom. On a humid August night in a room at 78°F, no mattress technology will rescue you; a fan and a thermostat will.
See Layla copper-infused memory foam
Phase change material: the most sophisticated option
Phase change materials are the only approach that regulates in both directions. The material is engineered to melt — to change phase — at a temperature close to the skin. Melting absorbs energy without the material getting hotter, which is why it can hold a surface near a target temperature rather than simply slowing the warm-up. When you cool down later in the night, it solidifies again and releases that stored heat back.
It is used more often than people realise. 5 Little Monkeys builds Dual Phase Change Gel into its kids’ mattress alongside an open-cell memory foam structure — a sensible pairing, since children are notoriously bad at regulating their own temperature and worse at doing anything about it. Organix Bed uses PCM in pillows under the CarbonCool and OmniPhase names, where the effect is arguably more noticeable because your head is the warmest thing touching the bed.
Why your bedding may be undoing all of it
This is the part the mattress industry has little incentive to tell you. Every cooling technology above works at the surface of the mattress. Between that surface and your skin sit a mattress protector, a fitted sheet and often a topper. If any of those is a sealed vinyl-backed protector or a dense polyester sheet, you have insulated the very layer you paid extra for.
Two practical fixes matter more than most mattress upgrades:
- Choose a breathable protector. Waterproof and breathable are not mutually exclusive — a cotton jersey face with a thin non-vinyl membrane behaves very differently from a plastic sheet.
- Choose a breathable top layer. Natural fibres move moisture better than synthetics, which matters because much of what feels like “sleeping hot” is actually trapped humidity rather than trapped heat. Wool is unusually good at this: Sleep & Beyond describes its myMerino comforter as four-season precisely because wool moves moisture vapour away rather than holding it.
How to read a cooling claim honestly
Ask three questions of any product page:
- Which mechanism is it? If the page says “cooling technology” without naming copper, graphite, gel, phase change or open-cell airflow, there may be nothing behind it.
- Where in the mattress does it sit? A cooling layer buried three inches down does far less than one in the cover. PCM in particular needs to be near the surface.
- Is there a trial? Heat is subjective and depends on your room, your bedding and your metabolism. A generous in-home trial is worth more than any claim on the page.
The honest summary
If you sleep hot, the ranking that matters is roughly: fix your bedroom temperature first, fix your bedding second, and choose mattress cooling technology third. Within that third category, open-cell airflow is the most reliable because it cannot wear out, phase change material is the most sophisticated, conductive infusions like copper give a real but modest benefit, and gel is the weakest because it saturates.
None of them will make a mattress cold, and any product that promises they will is overselling. What they can do is stop a foam mattress from being noticeably worse than the alternatives — which, if you have ever woken up stuck to a memory foam bed in July, is worth having.
See phase change gel in a kids’ mattress
Frequently asked questions
Will a cooling mattress actually feel cold to the touch?
No, and any product promising that is overselling. Passive cooling technologies move, absorb or buffer heat — none of them refrigerate. A gel or phase change surface can feel briefly cool when you first lie down because it is at room temperature and conducts heat away quickly, but that sensation fades within minutes as the layer equalises with your body. The realistic goal is a mattress that does not get noticeably warmer than the room, not one that feels chilled.
I sleep very hot. What should I fix first?
In order of impact: bedroom temperature, then bedding, then the mattress. A room at 78°F will defeat any mattress technology, and a sealed vinyl mattress protector will cancel out a cooling layer you paid extra for. Only once the room and the bedding are sorted does the mattress construction become the limiting factor. This ordering saves people a great deal of money, because the first two fixes are far cheaper than the third.
Does gel in a mattress stop working over time?
The gel itself does not degrade in any meaningful way, but it does saturate every single night. Gel works by absorbing heat, and once it has absorbed as much as it can hold it offers no further benefit until it cools down again — which happens during the day when you are not in the bed. So gel helps most in the first part of the night and least in the early hours, which is the opposite of what many people need.
Are cooling mattress pads and toppers worth buying?
Often yes, and they are the highest-leverage fix if your existing setup has a breathability bottleneck. A breathable topper over a warm foam mattress can meaningfully change the surface temperature, and it costs a fraction of replacing the mattress. The one caution is that adding any layer between you and the mattress reduces the effect of cooling technology built into the mattress itself, so do not stack a dense topper on a mattress you bought specifically for its cooling cover.
Is memory foam always hotter than a hybrid or innerspring?
As a general tendency, yes, for two structural reasons: foam is a good insulator, and it conforms closely to the body, which reduces the surface area available for airflow. A coil unit leaves a large open air cavity beneath the sleeper that foam simply does not have. Modern open-cell and perforated foams narrow the gap considerably, and a well-designed foam mattress can outperform a poorly designed hybrid — but if heat is your single biggest complaint, a hybrid starts from a structural advantage.
Related reading on Sleeping Express: mattresses for hot sleepers and waterproof protectors that do not trap heat.
