Hi rupekate,
Your wife posted a similar question previously and I responded to ithere.
In summary:
It’s not really 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.
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 or foam toppers will tend to be more “insulating” and for some people can sleep warmer than firmer versions of the same material.
I would tell you to read completely the post #2 I linked to earlier in this reply, as it does go into more detail about temperature regulation. You may wish to take a closer look at the top-of-bed products you’re using, as you’ve gone through three mattresses in seven weeks, and these top-of-bed items would have been a constant and perhaps they are contributing to your heat issues.
While natural fibers can be quite breathable, it depends upon the type of natural fiber being used and also the quantity, along with other materials used within the mattress. The more you are “in” the mattress, the more insulating the material will be (wool regulates temperature in both directions – warms and cools), so this can have an impact as well on your sleeping environment. A firmer surface comfort can often sleep cooler to individuals, as you’ll be “on” the mattress more than “in” it. An innerspring mattress using thinner layers of latex, natural fibers or even polyfoam can be quite breathable. Even coil on coil designs (pocketed springs with microcoils on top or microcoils in a topper) can also be very breathable.
Phoenix