Hi sb,
There is more information in post #2 here that can help you track down some of the possible reasons for temperature issues in a mattress.
While there is some overlap between different foam materials … in general terms latex is the most breathable and temperature regulating of all the foam materials (Talalay even more than Dunlop). With foam materials … softer layers will also tend to sleep warmer than firmer layers because you will sink into them more deeply and they will be more insulating.
Fibers are even more breathable than any foam material though and natural fibers like wool tend to be more temperature regulating than synthetic fibers because they can store moisture inside the fiber away from the body so that the microclimate around your skin is less humid (which feels cooler). This is why it’s used in both arctic climates and desert climates but of course it is also used in thinner and lighter layers in the desert than it would in the arctic.
Because wool regulates temperature in both directions … if the wool layers are thicker then it may be maintaining a temperature that is higher than you are comfortable with and this could also be an issue for those that are closer to the oven end of the “oven to iceberg” range. This would be especially noticeable in warmer or more humid weather or if you don’t compensate for the higher temperature with thinner blankets or different sheets and bedding.
Your sheets and bedding can also make a difference (synthetic fabrics will tend to be less temperature regulating and warmer than fabrics that are made from natural fibers or semi synthetic fabrics such as various types of viscose rayon materials).
There is more about the different types of mattress protectors in post #89 here and while I’m not familiar with it … the Secco mattress protector looks like one of the thinner “membrane” types of protectors (the membrane is the polyurethane layer) which tend to be less breathable than wool and for most people would tend to sleep warmer than a thin wool/cotton protector because they will allow less airflow through the protector (this is the tradeoff for being waterproof).
Of course each person’s experience may be different or unique so the best way to know how hot or cool you will sleep on any combination of mattress surface layers along with the protector, sheets, and bedding you are using will be by actually sleeping on it but “theory” along with most people’s experience would indicate that the Secco would likely be a little warmer than the Dormeir wool/cotton protector.
Phoenix