Hi rvsarch,
The “hand feel” of most gel memory foams will be noticeably cooler than regular memory foam and they can provide some cooling benefits when you first go to sleep at night but temperatures will tend to equalize over time at which point the insulating properties of the memory foam will become dominant. The amount and type of gel in the foam can affect whether the temperature benefits will last longer or shorter and the cell structure and amount of airflow through foam will also play a very significant role in reducing heat buildup in the material but in general terms … gel memory foam can sleep a little cooler when you are first going to sleep at night but in most cases the benefits of the gel tend to be temporary and don’t normally last over the course of the night. Gel memory foams in general will also tend to be somewhat faster responding than non gel memory foams as well.
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 … 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.
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. The sheepskin mattress pad that you are using would generally be enough to keep most people in a suitable temperature range even on top of memory foam (which in general is the warmest type of foam material) although of course there will always be some exceptions.
Memory foam or to a slightly lesser degree gel memory foam in general will tend to sleep warmer than other types of foam materials such as polyfoam and latex and all foam materials will tend to sleep warmer than natural fibers such as wool or cotton but there are many different formulations of memory foam and gel memory foam that are being used in the industry that can vary in terms of airflow and temperature regulation. There is more information and comments about some of the different methods or formulations that can be used to help cool down the tendency of any memory foam to sleep warmer for some people in post #6 here but memory foam manufacturers don’t disclose their specific chemical formulations and there are so many variables involved in temperature regulation other than the memory foam formulation itself that the only way to know whether any memory foam mattress in combination with all the other variables that can affect temperature regulation will be “temperature regulating enough” for you will be based on your own personal experience.
I’m looking forward to finding out what you end up deciding and to your comments and feedback once you’ve had the chance to sleep on it for a bit.
Phoenix