Hi holemania,
Welcome to the Mattress Forum! :cheer:
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. 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.
(In addition to the information presented below … post #29 here has more information about temperature regulation and the microclimate on a mattress.)
There are many factors which control the sleeping temperature of a mattress and only one of these is the foam that is used in the mattress … particularly in the upper layers.
There are 3 main types of foam which is memory foam, polyfoam, and latex. Of these three … memory foam tends to be the most insulating and least breathable followed by polyfoam and latex is the most breathable. Talalay tends to be more breathable than Dunlop. There are also variations in each category and less dense foams tend to be more breathable than denser foams while firmer foams tend to allow less sinking in which can mean there is less insulating foam material against your body.
All foams are insulators (rather than heat conductors) so to some degree they will all be warmer than mattresses that contain no foam at all (such as mattresses that only have an innerspring and layers of natural fibers on top) but these tend to be premium or super premium mattresses and for the most part almost all mattresses have some type of foam in the comfort layers.
Some of the other factors involved in how warm a mattress sleeps are how closely the foam conforms to your body (the more closely it conforms around you the more insulating it is, and softer Talalay certainly will conform well like memory foam), how soft or thick the foam in the comfort layers are (the softer/thicker it is the deeper you will sink into the more insulating materials, and your mattress has 2" of Talalay on top of 2" of Dunlop latex), the type of quilting used in the mattress (natural fibers allow for more airflow and humidity control which translates into better temperature regulation), the type of ticking (cover) used (natural or more breathable fibers such as cotton or viscose or even some of the more breathable synthetics will wick away moisture and ventilate better and humidity control is a key part of temperature control, and your mattress uses a cotton cover quilted to a silica/rayon FR barrier), and on any cooling technologies used in the mattress such as ventilating and moisture wicking materials, heat conductive materials, or phase change materials (you can read more about these 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 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.
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 (your mattress uses a polyfoam support core) as long as the air can ventilate to the outside of the mattress.
In addition to this … 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 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.
Overall, comparing your current mattress to the old memory foam mattress you said you used before is a bit of a moot point, because there are so many variables involved that could be different, including, but not limited to, the foam used under the top memory foam layer in the old bed, the core used (innerspring or polyfoam), the overall thickness of the mattress, the FR barrier used (or if it had one, pre-2007), they type of foundation used (placed upon a breathable slatted base or solid box that inhibits air circulation), the mattress pad/protector used, the fitted sheet used, flat sheet used, blankets used, the sleeping environment (humidity, temperature, air circulation), and the most important variable – you (changes over time in your physical condition, temperature sensitivity, pajamas used, etc.).
With all of that being said, you may wish to consider a few things. Check the foundation being used and make sure that it is allowing sufficient air flow. If you’re on a solid surface, consider something like a coir bed rug under the mattress. For a mattress pad, you may wish to consider a thin wool mattress pad, as it has excellent characteristics in being temperature neutral. If you decide to get a mattress pad with some sort of phase change materials, look for something thinner and realize that this sensation of feeling cooler is a more temporary effect. Consider the clothing you’re wearing when you go to sleep, and then move on to the sheets and upper insulating layers. Also, make sure your bedroom temperature is somewhere in the mid-60 degree range with a lower humidity. I know it’s a lot to consider, but the links I’ve provided above can be assistive in creating the most comfortable microclimate possible for you.
I’ll be interested to learn about how you progress through your evaluation and any changes that you are able to make.
Phoenix