Hi aldel,
This would be controlled the chemicals they use in their formula and by the specifics of the foam manufacturing process which would both be proprietary to the foam manufacturer (and probably not understandable to someone that doesn’t have a degree in materials science).
Outside of knowing the specifics of “how” a foam manufacturers makes a specific foam … in general terms a more breathable foam has more open windows in the cell structure of the foam that allows for greater airflow. There is also more about some of the methods that can be used to affect the temperature of memory foam in post #6 here.
Since foam manufacturers don’t provide all the information you would need to assess the temperature regulation of a specific foam material based on specs (assuming a consumer could understand them in the first place) and there is no specific comparative information that I’m aware of anywhere that compares the hundreds of different types of foam (or different mattress designs) in terms of sleeping temperature, not to mention that it’s always a combination of many factors that includes the effects of every layer and material in the mattress and the bedding materials you use that will determine temperature regulation … the best way to assess how a mattress will perform for you would be a more detailed conversation with a knowledgeable and experienced manufacturer or retailer that has your best interests at heart who will know more about the “real world” performance of their mattresses and the combination of materials they use than anyone else.
Phoenix