Fed up of sweaty sleep? Simba's new HeatRelease technology keeps you 4.4°C cooler all night long

If you've spent this summer waking up drenched in sweat, tangled in a duvet you can't decide whether to kick off or cling to, you're not alone, heat is one of the most common reasons we lose sleep, whether that's down to a heatwave, hormones, or a bedroom that won't cool down after dark. Plenty of mattresses claim to help, working hard with natural materials that wick moisture, breathable structures, and gel layers. But nobody's delivered results quite like Simba.

Simba is already well established for making the best cooling mattresses on the market. Their tech team is forever testing, measuring and trialling new materials, designs, and innovations and their latest is HeatRelease. It's a technology officially measured in trials to keep you up to 4.4°C cooler from falling asleep right through to when you wake up. When you're sleeping through a heatwave or riding out hormonal night sweats, that's enough to change your sleep significantly.

The technology hasn't rolled out across the full range yet, but it's already in some of my favourite Simba mattresses. Here's everything you need to know.

Simba Heatrelease Mattress Range Launch

Hot on the heels of their new made-to-order bed range, the new HeatRelease feature works through a layer of graphite-infused strips, positioned to draw excess body heat away from you as soon as you lie down. Simba says it starts working within 20 minutes and keeps going for the full night. So it's not just a cool feeling when you go to sleep, it's right through to the middle of the night and the early morning when night sweats are at their most fierce and unbearable.

The strips work alongside two things Simba is already known for: graphite-infused Simbatex foam, and Aerocoil microsprings, which are designed to let air circulate through the mattress rather than trap it the way solid foam can. Together, the combination is what gets you to an impressive, tested statistic: these mattresses keep you 4.4°C cooler than sleeping without it, measured in independent trials, and maintained for up to eight hours.

To put that in perspective: 4.4°C is roughly the difference between a mild night and one where you're kicking off the duvet every hour. So whether it's a hot night because of hormones, a heatwave, or a bedroom that just doesn't cool down after dark, it's a temperature difference that will change how you feel.

It's currently available on the Simba Hybrid Ultra as standard, with an optional HeatRelease upgrade on the Hybrid Pro and Hybrid Luxe. It's exclusive to Simba in the UK, and every mattress in the Hybrid range comes with their usual 200-night trial, so there's room to test whether it delivers for you specifically before committing.

Simba's CEO, Steve Reid, puts the timing down to Britain's changing summers: "Britain's homes are getting hotter, bedrooms becoming overnight heat traps, and people are looking for smarter ways to stay cool while they sleep. That's why cooling has become one of the biggest priorities in sleep innovation. Our customers want mattresses that actively respond to the environment around them. HeatRelease combines advanced thermal engineering with our latest sleep technology to draw excess body heat away from the sleeper, helping people stay cooler and sleep more comfortably, even during Britain's hottest nights."

Simba cooling products

For the best set up, we recommend making as many cooling tweaks to your bed as you can. That means using cooling sheets, a cooling pillow, and a cooling topper. Here are our favourites:

If night sweats or this summer's heat have made your bed unbearable at times, HeatRelease is worth putting on your shortlist. It's one of the more convincing cooling claims I've seen backed by an actual trial figure, rather than a vague "breathable" promise. Ready to feel the difference for yourself? Take a look at the latest Simba deals.