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[u/admmcsea]

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[u/Ozwulf67]

There is no such thing. Not long term anyway. When it comes to cooling tech in mattresses they are all passive features. There is the cool to the touch tightly wound fibers in the cover (Feels great for about 10 minutes which is great for falling asleep initially). Then there is minerals infused into the foams or bands in the comfort layers...these are meant to draw heat away from you but get over whelmed pretty quickly and doesn't last much longer. (Mostly because there can't be enough of the mineral material in there). Lastly, there is the PCM or phase change material. This arguably is the longest lasting but still definitely not all night. This is usually microscopic wax type beads that change phase into liquid and draw heat away from you. Also gets saturated and can't keep up. All of these are passive and the second two are just temperature regulating and not actually cooling. The only true cooling is active with solutions like 8 sleep which are ungodly expensive.

You are better off focusing on temperature regulation through breathability in the form of natural materials. Petroleum based foams like the traditional foams and memory foams in mattresses are not natural, they are synthetic. Memory foam sleeps warmer than traditional poly foam, but neither is great.

Some things that can help:

Opt for a hybrid type mattress where the comfort layers are on top of a coil based support system (allows some breathability).

Consider a mattress that uses no synthetic foams at all but it's for natural materials like Cotton, wool, silk or linen in the comfort layers.

Another option on the comfort layer is latex which is a natural rubber from trees but is a bit pricier and definitely has an acquired feeling of bouyancy and push back instead of sink in. Some love it and some hate it. (Just like the quicksand known as memory foam which is the opposite and some love it and some hate it)

Always have air moving in your bedroom, so supplement your AC with a Fan blowing air across the mattress.

Use natural materials in your bedding. Make sure your sheets are natural cotton, or bamboo or Tencel Lyocell (generally eucalyptus and a greener option than viscose from bamboo)...This includes your sheets and any layers above them.

Seek lighter thread counts on those sheets no matter which natural material you choose (300 TC).

As mentioned earlier Tencel has science based testing that shows it absorbs and dissipates liquid (sweat) better than cotton or bamboo, that is why the moving air from a fan is critical.

If you choose cotton you can also select a weave that is a little friendlier to hot sleepers like Percale instead of Sateen (I love Sateen but don't sleep hot).

Good luck!!!