Hi MIRDLR,
I still don’t know the blend of the latex or if you’re comparing from within the same brand using the same latex.
Assuming that it’s the same brand and the same type/quality of latex, then your difference is just as you described – the addition of the memory foam (and I’m assuming the extra latex layer that you left out in your follow-up post).
It’s not really possible (for me or any salesman) 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.
Regarding cooling memory foam claims, you can read more about phase change materials in post #9 here and at the end of post #4 here) and you can read more about the various different types of gel foams with quite a few good links in post #2 here. In general terms gel foams will tend to have a temporary effect on temperature while you are first going to sleep until temperatures equalize but have less effect on temperature regulation throughout the course of the night. This effect is of course felt less in the deeper layers of the mattress. While newer memory foams are being designed to be less “heat retentive” than their counterparts from years past, many of the advertising claims should be viewed with a fair amount of skepticism.
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. While the upper layers of a mattress are the most significant part of temperature and moisture regulation … deeper support components that allow more airflow can also have an effect and so innersprings will also tend to sleep cooler than foam support cores as long as the air can ventilate to the outside of the mattress.
As you would rend to “sink in” more on the second mattress with more materials, effectively surrounding your body with more foam “insulating material”, and you have the memory foam layer (even though it is deeper down in the mattress), from a “theory at a distance” this product could certainly “have” the ability to sleep warmer than the other item to which you are comparing. As temperature regulation is important to you, this is something you’d certainly want to take into consideration.
Phoenix