In this series of blog posts, my goal is to attempt to discuss topics that are often brought up by not just consumers, but players in the mattress industry and hopefully give some perspective to these topics. So do some mattresses sleep hotter than others? Should this be a concern for everyone? The reality is that if you’ve been sleeping on a conventional mattress and heat wasn’t an issue, then most current mattresses should not sleep that much hotter for you. Conventional mattresses use synthetic foams and fibers that do not breathe and often hold moisture. Which can certainly contribute to sleeping hotter.
So why is “sleeping hot” such a “hot” topic currently, excuse the pun? This subject has been discussed more over the past 10 years or so. When Tempur-Pedic started to become popular, “sleeping hot” was one of the criticisms that other mattress manufacturers would focus on. It was natural to associate heat with Tempur-Pedic due to the name. Tempur-Pedic responded by explaining that the Tempur foam had an “open cell structure”.
So what are the facts about sleeping hot? First the major source of heat in your mattress is the person that is sleeping in it. Do some people generate more heat than others? Absolutely yes, my ex-wife would tell me she could feel the heat from my body from 5′ away, I have a very high metabolic rate. Do certain materials trap that heat and others dissapate it? Well we know that synthetics don’t breathe well, while natural fibers do breathe.
Does air circulate through foam? The 2 most popular foams that are rated high in terms of performance are memory foam and latex. They both claim “open cells”. But you have to understand that the reason they both perform well in terms of support and durability is that they are both very dense foams. A quality memory foam or latex mattress weighs as much or more than a quality innerspring mattress. Will air flow through small openings as easily it flows through larger openings?
A good comparison is the current very popular mattress protector technology. They are waterproof, but still allow some airflow. One of the common demonstrations of this is that they will have a jar with glass cleaner liquid inside. The jar is sealed at the top with the mattress protector material. The jar is turned upside down to show that the liquid does not escape and then you are instructed to smell and you can smell the ammonia of the glass cleaning solution inside the jar. That demonstrates that it is a selective membrane that has openings too small for liquid, but air can still flow through. However we would still have a few customers that would complain about “sleeping hot” in a mattress that we knew should not sleep hot. They would be using the mattress protector, and we would ask them to sleep without the mattress protector. They would not have the heat issue when they did not use the mattress protector. Even though the mattress protector membrane would allow some air to flow, the openings are extremely small and so the air does not flow as freely as say through pure cotton or wool.
Another reason you might sleep hotter in a mattress is if you lay deeper into it. Your body heat will heat up the area that you are laying in quicker, because more of your body is in contact with the sleep surface. Also if you move less frequently as many do in a memory foam mattress, your body heat will build up around you for longer periods and so it will be perceived to sleep hotter. Less tossing and turning can provide more restful sleep, but if you wake up hot, it can negate that benefit.
What will sleep cooler? definitely having a breathable layer immediately beneath and if it’s wool, that layer can also help reduce humidity around you since the wool wicks moisture away. Coils will definitely allow the air to circulate more freely than sold foam. Also quality handmade mattresses often have air vets, like Vi-Spring from England. Their mattresses use only natural fibers, including wool and pocketed innersprings that have natural calico cotton encasements and air vents that go completely around the entire mattress.