Hi Needforsleep,
As you probably suspected, I missed the original post and only read the second one … sorry.
In case you haven’t seen this … the Seattle thread with some of my comments about some of the retail outlets and manufacturers there are in post #2 here.
If this is your biggest concern then memory foam or gel foam would have the best performance in this area. Latex is also very motion isolating by most people’s standards but it does allow some vibration to come through and would be less motion isolating than memory foam (or its variant gel memory foam). Latex is a resilient and elastic material and returns most of the energy when it compresses while memory foam has much higher hysteresis (absorbs energy) and is less responsive but more energy absorbing.
Latex is generally the coolest of the foam materials (memory foam, polyfoam, latex foam) and Talalay latex is more open celled and more ventilating than Dunlop latex. There are many factors involved in sleeping cool however which includes the foams used in the top layers of the mattress, the quilting and ticking layers, how deeply you sink in to the mattress, the mattress protector, the sheets and bedding, and any temperature regulating technology used in the mattress. All of these work together to control temperature and one layer can sometimes negate the layers below it so it’s important to make sure that all the layers work together. Temperature regulating combinations of materials are more effective than single “pieces” of the puzzle.
There is more about sleeping cool and the factors that are involved in post #2 here which also includes a link to a post about the three main technologies or methods used to regulate temperature (including different types of gel materials).
By my estimation this would be on the firm side for a side sleeper but each person is different so one person’s firm is another persons medium or soft. The 6" core in this mattress is more in the medium range than firm though which may be why it was OK for you.
There doesn’t need to be an actual separate comfort layer in a mattress as long as the top surface is soft enough to form a cradle that is deep enough to redistribute weight and relieve pressure. For example a soft 6" Dunlop core may work well for some people even though it has no comfort layer at all because the top inch or two would be soft but as you sink in deeper it would rapidly get firmer so in this case you would have more of a “comfort zone” (the top part of the layer) and a “support zone” (the deeper part of the layer) all in the same layer. In most cases though … there is a separate comfort layer but how thick and soft it needs to be is greatly affected by the layers below it.
You can read more about the different types of construction that can affect all the other guidelines (including the thickness and softness of a comfort layer) in the “putting the layers together” section. Easier yet though is to bypass the more complex mattress design theories and to test carefully and “believe” the feedback from your body using the guidelines as a reference only. If you were completely relaxed on the mattress (like the pre-sleep state) and spend at least 15 minutes lying on it and there was no sign of pressure then it would likely be fine for you but I would make sure of this because it would be on the firm side. A mattress like the Woodlawn would be more typical for a side sleeper but personal testing always trumps “theory at a distance”.
This would be a different feel from the Dunlop and I like removable toppers because they can be replaced without having to replace the whole mattress (upper layers wear out faster than deeper layers even in latex). The advantage of a two sided mattress vs a topper is that it will add to durability (the upper layers are only used half as much) and longevity.
Again … this is something you could test for in the store to make sure that the degree of motion isolation is acceptable to you. It would be better than other types of mattresses but not as good as various types of memory foam and your own preferences would be the most important factor.
Gel memory foams are the latest “rage” in mattresses and almost every manufacturer is making a version because of the success of the Serta icomfort (which is much lower quality mattress but has a nice showroom feel and a price tag that is too high). the Therapedic gel foam lineup uses good quality mateials and is one of the better ones available from a major brand. There is more about gel memory foams and the different types used in post #2 here. The Therapedic uses the type of gel memory foam that has the two materials mixed together rather than adding gel as particles (which is a less desirable method).
Seattle mattress tends to be on the high side in terms of “value” though and in the testing I did in Seattle I generally found that they were not in the same “value range” as Bedrooms and More or some of the other Seattle options even though they are a manufacturer. As an example … a retail store that I think very highly of (not in Seattle though) carries the Blue Essence here for a pricing reference (their prices are very good).
So overall it would seem that a gel foam mattress would be a good choice for your needs and preferences and it seems that you prefer it over latex. While latex would be more durable … the gel memory foams and other higher quality materials in the Blue Essence also are durable materials. There is no “junk foam” in this mattress and even the base layers are good quality.
All foam mattresses are fine on a platform bed which doesn’t need a foundation (it’s optional for height). It wouldn’t make any difference to motion isolation though because they would both be a firm rigid base with no movement. The platform bed should have rigid, non yielding slats that are no more than about 3" apart (this has better ventilation than a solid surface although there are also many people who believe a solid surface is fine) and a center beam with support to the floor.
You have a few other good options in the Seattle area but you have already done some good testing so far and it seems that based on your preferences the Therapedic would be a good choice at the right price IMO.
The goal is always to narrow things down so you are choosing between good and good and I would make a few more calls to some of the outlets on the list (and ask them about any latex or gel memory foam mattresses they carry and visit the ones that are most promising). I don’t think you’re quite there yet but you’ve made a good start and identified some of your preferences and the differences between materials so you are making more informed choices.
Phoenix