Hi udoknowjac,
I did talk to Rocky Mountain Mattress (they called me back) and they were surprised that you (or any of their customers) hadn’t received a call back and they said they would talk to their customer service staff to find out what may be happening. It’s certainly not the norm for them.
Memory foam is a warmer and more insulating material that stores heat more than other faster responding types of foam but if I was looking to lower the sleeping temperature then I would first look at the parts of your sleeping system that were closest to your body. With a topper this would include the topper cover, the mattress protector, and your sheets and bedding. Your Tempurpedic already has a mattress cover and it’s also under the topper and deeper inside your sleeping system so that isn’t something that I would consider changing.
If you are considering a topper cover (not a mattress cover) I would probably go with a knit cover made from either cotton or a viscose type of material such as a bamboo blend which are breathable and does a good job wicking moisture. It wouldn’t have to be waterproof because you would also have a mattress protector.
For your mattress protector I would consider either a stretch cotton or even better a wool/cotton protector which is more water resistant and where the wool can provide better temperature regulation even though it may have a little more effect on your mattress. I would use the protector over the mattress and the topper.
There is more about sheets and bedding in post #7 here but I would probably look at natural or “semi synthetic” fabrics here as well which includes cotton, viscose (again such as bamboo, tencel etc), or linen (which would probably be the coolest of the natural fibers but they are also much more costly).
These would probably be the most effective changes with the memory foam materials you are currently using and hopefully they will make “enough” difference that you can sleep a little cooler.
These are mattress covers … not topper covers. I don’t know if they sell topper covers but I would certainly call and ask.
I’m not familiar with them no or how stretchy they are but the bamboo would probably be a little cooler (more breathable and moisture wicking) than the cotton.
Phoenix