Hi lrhodes,
Your budget of $1000 - $1500 for a King Size would certainly allow you to use a latex comfort layer over various types of support layers which would give you many of the benefits of sleeping on latex. Depending on the thickness and type of latex and personal preferences … the top of your budget is just in the range of an 8" all latex mattress (@2" over @6"). Of course you would almost never find this type of value outside of local independent manufacturers or DIY manufacturers such as some of those that are members here.
Part of the reason memory foam sleeps hotter than other foams is that you will sink more “into” a memory foam comfort layer than other foams. It also is a more “insulating” type of foam than others because the internal cell structure is not as open as regular polyurethane foam and much less open than latex. It also forms itself around your body more closely which again is more insulating. How hot each person may feel on any individual memory foam mattress would depend on the type of memory foam used (not the brand of mattress), the density of the memory foam, the weight of the person (heavier people will sink in deeper), and perhaps most importantly of all … the individual metabolism and tendency to sleep hot anyway and where you are in the “oven to iceberg” range.
There are several ways that individual foam manufacturers are using to try to reduce the sleeping temperature of memory foam mattresses. One of these is using more open celled memory foam. More open cells allow more airflow inside the memory foam which results in cooler foam. It will also be faster responding than typical memory foam. Many manufacturers are using various chemical and mechanical manufacturing methods to produce more open celled foam … and memory foams like Aerus memory foam manufactured by FXI which uses variable pressure foaming or many of the other newer generation more open celled memory foams are an improvement and more breathable than the older generation slower response memory foams.
Lower density memory foams also tend to be cooler since they tend to have a larger more open cell structure however they are also less durable, have less "memory, and can be less conforming. Lower density can also result in a faster recovery time (less “memory foam” like). 4 lb memory foam in other words can be more breathable than 5 lb memory foam but less durable.
Other manufacturers are using various combinations of holes punched in their memory foam or different types of airflow channels in the memory foam or the polyfoam underneath it to encourage airflow. These are often less effective than more open celled foam … although this can depend on whether these airflow channels actually stay “open” and allow airflow from the body surface to the outside environment during actual use.
Other manufacturers are putting gel or other conductive or phase change materials inside the memory foam because in theory they will conduct heat away from the body (thermal conductivity) or can store and and release heat (phase change materials) to help regulate temperature. These gels are quite heavy and they become part of the memory foam itself. The reviews on these are mixed and my own personal opinion is that it they can make a small difference in temperature (if the gel foam is on or very near the surface of the mattress) … although that difference may be a bigger improvement for some than for others and tends to be temporary and only lasts until temperatures equalize. In other words they can help while people go to sleep but not over the entire course of the night depending on the percentage of gel in the foam. The gel may also make a memory foam appear to have a higher density (durability) than it really does since it is denser than the memory foam it’s added to. In other words … it can make lower density/quality memory foam weigh more and appear to be higher quality but in general the density of gel memory foam can be compared to regular memory foam of the same density in terms of durability.
Some information about the different types of gel memory foam (and other gel materials) available in the market is in post #2 here. There is also a brief outline of the three main cooling technologies (thermal conductive materials, phase change materials, and ventilation/humidity control) that can affect sleeping temperature in post #9 here.
Many manufacturers are using various temperature regulating covers (tickings) in their memory foam mattresses which can help reduce heat. Others yet are using various forms of quilting in the ticking (such as highly breathable low density polyfoam or various natural and synthetic fibers) over the memory foam to encourage air circulation, evaporation and moisture wicking, and cooling. The side effect of this is that the memory foam is further away from the body heat which can no longer “soften it” as easily which can make the memory foam feel firmer for some or take away from the feel of the memory foam which they prefer.
The bedding layers used on top of the mattress (mattress protectors, mattress pads and toppers, sheets etc) will also play a major role in sleeping temperature and in some cases the primary role because they are the closest to the skin and can either add to or reduce the effectiveness of the layers and materials below them. There is more about the many variables that can affect sleeping temperature in general in post #2 here.
All in all it is a combination of all these factors (physiological factors, types of memory foam, other components and technologies, and bedding) which determines how hot someone will sleep on any memory foam mattress (or any mattress for that matter). Personal testing over a long enough period of time is really the only way to know for certain how “hot” any particular mattress will sleep for any particular individual however knowing the cooler types of mattress components and materials and the knowledge and experience of a salesperson or manufacturer based on longer term customer feedback can also be very helpful to predict how cool a particular mattress may sleep for any particular person.
There are many types of gel memory foams made by many manufacturers and they have been used in several variations for years (microencapsulated beads, particles, liquid infusions various minerals etc) although they have recently been much more heavily advertised and become more popular. I would compare them to regular memory foam in terms of value as I believe that the amount of gel in most of them is not enough by itself to make a significant temperature difference in “real life” over the whole course of the night for some … although it may just be that extra piece that in combination with other factors works well for others at least for a period of time. There is not a lot of evidence and publicly available factual information that justifies the somewhat exaggerated claims of gel foams in general compared to other methods of effective cooling (or better yet combinations of different methods) but they can certainly be one piece of the puzzle.
The tradeoff in using gel foams would be how much does the particular type of gel affects the durability or properties of the memory foam itself and how much is the current marketing emphasis on new “cool” technologies and the stories attached to them actually adding to the cost of the mattress compared to effective technologies and materials that have been in existence for longer and that may be overlooked.
From looking at the pure comfort topper … it is made of 3.25 lb memory foam (the mattress doesn’t list the memory foam density). This is very low quality and for some people may only last for weeks/months although for others it may last longer. I wouldn’t tend to choose memory foam below 4 lbs unless you are comfortable with the probability of lower durability.
The Novaform “gel” memory foam doesn’t list the density of the foam.
I personally would not buy any memory foam without knowing its density and the quality and type of layering underneath it. While you would certainly be “rolling the dice” with any online purchase of an “unknown” memory foam or mattress construction … at least Costco allows a return at no cost if the mattress isn’t suitable for you.
If your baby will be using the mattress at all … I would avoid memory foam completely as it is unsuitable for babies and infants. I personally would never put a baby or infant (or even a young child) on memory foam (see post #2 here).
There is no “standardized” testing for the “sleeping temperature” of different memory foams and what feels OK for some will be hot for others … especially in combination with other factors that may contribute to sleeping warmer. If you have tested a specific type of foam or manufacturing method or cooling method for a few nights (not just a few minutes in a showroom) … then this will certainly be much more accurate for each individual.
Overall though … memory foams as a group are warmer than other foams. How much warmer would depend on a combination of all the individual factors I mentioned.
Phoenix