Hi Happyday:
As you know, temperature regulation while sleeping is a complex process, with every layer having an overall effect upon the complete system. I’m including quite a bit of information here just in case someone comes across this thread and desires more detailed information upon the subject. The most important information about mattress protectors is in the first paragraph below.
The mattress protector you choose along with your sheets and other bedding and what you wear when you sleep will also have a significant effect on temperature regulation because they can either add to the insulating effect or to the ventilating and moisture wicking effect of your mattress. You can see more about the effect of different mattress protectors (and the difference that encasements can make) in post #89 here.
Bedding made from natural fibers or viscose materials (like bamboo) will also tend to be cooler than synthetic fibers and linen sheets along with silk are probably the coolest of all the natural fibers for those where sleeping temperature is a main priority. There is more about sheets and bedding in post #7 here. In many cases changing the mattress protector, sheets, or bedding to cooler versions can make “enough” of a difference for many people who would otherwise sleep hot on a mattress.
All of this of course is separate from any environmental conditions in the bedroom (temperature and humidity levels with higher humidity adding to the perception of heat), on the physiology and tendency of the person themselves to sleep warmer or cooler and where they are in the “oven to iceberg” range, and on their weight and body type which will affect how deeply they sink into the foam layers of the mattress.
In other words, it’s always a combination of several interacting factors that determines the sleeping temperature of a mattress in combination with a specific person and environment.
While it’s not possible to quantify the sleeping temperature of a mattress for any particular person with any real accuracy because there are so many variables involved including the type of mattress protector and the sheets and bedding that you use (which in many cases can have just as significant an effect on sleeping temperature as the type of foam in a mattress) and on where you are in the “oven to iceberg” range and because there is no standardized testing for temperature regulation with different combinations of materials … there is more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here that can help you choose the types of materials and components that are most likely to keep you in a comfortable temperature range.
Latex in general is the most breathable and temperature neutral of all the different foam materials and memory foam is generally the warmest although there are many versions of every type of foam (latex foam, memory foam, polyfoam) that can vary in their breathability and temperature regulating properties.
In very general terms … the materials, layers, and components of a sleeping system that are closer to your skin will have a bigger effect on airflow, moisture transport, and temperature regulation than materials, layers, and components that are further away from your skin and softer mattresses will tend to be more “insulating” and for some people can sleep warmer than firmer mattresses.
Wool is one of the best temperature regulating materials (in both directions) that is used in the industry and is used in thinner layers in the desert and in thicker layers in the Arctic because of its effectiveness in regulating temperature. If you have a latex mattress with a wool quilted cover and/or you are using a breathable mattress protector and/or you are using sheets that are made from natural fibers (such as cotton or silk or flax linen) or semi synthetic fibers (such as bamboo or other types of viscose/rayon fabrics) and you are using bedding that is appropriate for the temperature of your bedroom then it would be very unlikely that you would have any temperature regulation issues.
Phoenix