Hi organizer,
There are a number of things that can affect the sleeping temperature on a mattress (not the least of which is where you are in the “oven to iceberg” range) and there is more about the many variables that can affect temperature regulation and sleeping temperature in post #2 here.
The best way to track down where temperature issues are coming from would be to look at all the layers between your skin and the floor to see if any of them could be contributing to the temperature issue. Layers or materials that are closer to you and are more breathable and allow for more moisture wicking will help with temperature regulation issues while layers that allow for less airflow or moisture wicking that are closer to you can make them worse.
Your sheets are cotton so this shouldn’t be an issue unless they are a very high thread count which could make them warmer. Linen sheets are probably the coolest sleeping type of fabric but they can also be costly. I don’t know if you are using a mattress protector (or if you are using the cotton mattress pad to protect the mattress) but the “membrane type” of protectors can also affect temperature by restricting airflow through the top layers of the mattress. I would also check your cotton mattress pad to see if it is only cotton or whether there are other materials inside it (and only the cover is cotton) because this could contribute to temperature issues as well. There is more about how different types of mattress protectors can affect sleeping temperature in post #89 here. Finally the next layers down would normally be the mattress itself which includes the cover and the top layers of foam.
Your blankets and bedding and the temperature or humidity of the room can also make a difference if there are no layers underneath you that can be changed that are part of the underlying cause of the temperature issue.
If none of this solves the issue then softer or thicker layers of foam in the comfort layers can also be more insulating and it may just be that the memory foam in your mattress is so soft and thick (it has 4.75" of memory foam and an additional inch of "comfort foam) that you are sinking into it more deeply than a firmer mattress and the memory foam is more insulating around you (and it also has “regular” memory foam in the top layer) and this is part of the normal properties of memory foam so it may never be “cool” enough for you without some additional “help”.
Wool is among the best temperature regulating materials but I would also keep in mind that it regulates temperature in both directions (it’s used in the desert and also in cold climates because of this) so while it may not feel “cool” … it generally doesn’t feel “hot” either and it also helps to regulate moisture (which can trap heat) and reduce the perception of temperature that comes from higher humidity levels (similar to how temperatures feel cooler on less humid days than they do on more humid days). Wool may also reduce the amount of heat that reaches the memory foam so it can also firm up the memory foam or at least slow down the time it takes to become softer with body temperature.
In general latex is a more breathable foam than memory foam but no foam material is as temperature regulating as natural fibers so it’s “coolness” would be relative to other types of foam. Some people that are more of an “oven” will also sleep warm if they sleep directly on soft latex with no natural fibers or other breathable materials above the latex (or with a mattress protector that impedes airflow).
Other than this … materials (mattress pads or protectors) that are “more” breathable and temperature regulating that what you have in any of your upper layers (particularly natural fibers or rayon/viscose types of fibers), changing your blankets or the bedding above you, or changing the temperature and/or humidity of the room; more “active” methods of temperature regulation (such as the Chilipad here) can be a solution but outside of something like the Chilipad there may be no perfect solution that can be as “cooling” as you hope within the limitations of your current memory foam mattress.
It would also be worth mentioning that your face and head is also a major part of how your body regulates temperature and a cooler pillow can sometimes make a surprising difference in how warm you sleep as well.
Phoenix