Hi Sergio G,
The term “weightless” has no specific definition. It would apply to any mattress where you didn’t perceive any pressure points, tension, discomfort, or tension in any of your joints or tissues (including your back). It’s not specific to any material or mattress design but is a function of how well a mattress matches your needs and preferences in terms of PPP. One mattress may feel “weightless” to one person while to another may be very uncomfortable. The term even applies to a position on an adjustable bed (also called the zero gravity position) regardless of the mattress that is used on it (see here).
Tempurpedic also has a line of mattresses called their weightless collection which uses thinner layers of memory foam over a more resilient material underneath it which provides a more “floating” sensation than thicker layers of memory foam. Of course there are many other examples of this type of construction as well and some mattresses that feel “weightless” to a particular person may not have any memory foam in it at all.
[quote]So, till now I have these 4 options.
So quick resume, in order of price:
- memory 2.75", 5lb, flat, with Poly 3.54" and 3.12lb, Medicott Silverguard external cover. Firmness not eligible, fixed choice 2.5 (mid firm, supposedly for people from 150lb, but they say from 110). 269 euro
- Same densities ad shape, but the Memory is slightly thinner, 2.36", and the Poly thicker, 4.72 (I can only suppose that this would give more supportive pressure from below, but less weightless feeling. Am I right?). Firmness eligible 2 or 3. Cover of antibacterial Amicor. 299 euro.
- 3.15" memory of 4lbs, 0.8" Calipore under it, and 4" 2.8lb Poly (you were right, my mistake, it was not 4lb). Both foams shaped in waves with a 7 zones structure. Cover of Lyocell (not antibacterial). Firmness 2. 375 euro.
- 2.75 memory of 5.3lb, plus 5.12" Poly of 3.4lb. No shape. Antibacterial Amicor cover. Firmness eligible from 1 to 3. 379 Euro.[/quote]
All of these use good quality materials and there are no weak links in any of them in terms of quality/durability that I can see but of course they would all have a different “feel” and performance in terms of PPP and only your own testing or experience can tell you if a specific design and combination of materials is suitable or a preference for you. You can’t tell with any certainty how a mattress will “feel” from specs unless you have personal experience with very similar material combinations and designs.
The distribution of support under the different parts of your body would contribute to a subjective “weightless feeling” and the thickness of the memory foam in a mattress isn’t what creates this “feeling”. Your own experience is the only way to know how “weightless” this mattress feels for you.
Memory foam changes in softness based on temperature, humidity, the length of time it is compressed, and pressure and can continue to soften over the course of the night. This means that layers of memory foam that are thicker than you need can be a little bit more “risky” in terms of alignment because you can start the night in good alignment but as the foam continues to soften under the heavier parts of your body over the course of the night you could wake up out of alignment with pain or discomfort in your back. There is no specific amount of memory foam that can be used as a specific guideline for what is enough or not enough for any particular person because of all the variables involved in both the mattress design and each person’s physiology and your actual experience on a mattress is really the only way to know if a mattress is a good match for you. This risk of waking up with back pain or discomfort can be reduced by using thinner layers of memory foam that are “just enough” for the body type and sleeping style of the person on the mattress because if you are closer to the more resilient support layers that are not temperature sensitive then there isn’t as much “room” for the heavier parts of your body to sink down until they reach a layer that isn’t temperature sensitive.
Outside of testing an actual mattress “as a whole” with a more scientific method that simulates actual sleeping conditions and comparing it to the same test under the same conditions on a different mattress there is no way to objectively compare the exact durability of one mattress to another. The closest you can come is by looking at all the factors that can affect durability that are mentioned in post #4 here and the other posts it links to. In some cases the useful life of a mattress has as much to do with the person and where in their range of comfort and support the mattress falls in than it does on the actual materials themselves so the materials in a mattress may have softened “enough” that it leads to the loss of comfort and/or support for one person but not for another even though the amount of foam softening or breakdown in both mattresses may be identical. This wouldn’t show up in mattress durability testing which couldn’t take the variables of each person into account.
[quote]I also would like to understand something: is it true that the better performances come from a complete Mattress where the two foams are glued or anyway there together, rather than buying for example a Mattress plus a separate Memory Topper?
This was my initial intention, but a seller told me it was not a good choice.[/quote]
You can read a little more about the pros and cons of having glued layers vs separate layers (which would apply to a topper as well) in post #8 here. While a separate topper would act more independently, feel a little softer, and be a little more subject to breakdown from compression forces than the same material inside a mattress … it also has the flexibility of being able to replace it without replacing the entire mattress so over time the extra topper may last a little less time than the same material inside a mattress but being able to just replace the topper would have cost benefits over replacing the entire mattress when the top layers soften and break down.
The key is being able to test the specific mattress / topper combination you are considering for PPP because having two variables in your mattress choice (one for the mattress and then another one for a topper) can be more difficult than only having one variable in your purchase decisions. The same topper can feel different on top of different mattresses so knowing which topper to choose without testing the combination together can be almost as challenging as choosing the mattress in the first place. There are some topper guidelines in post #8 here that may be helpful if you decide to go in this direction but if you did this I would first choose the mattress and then use your actual experience on the mattress without the topper as a reference point to help you choose the most suitable topper.
Any two materials can work well together if the feel of the combination is what someone prefers. A “hybrid” comfort layer (whether as part of the mattress design or with a mattress/topper combination) with a relatively thin layer of memory foam over a more resilient layer like latex can combine the properties and “feel” of both materials which some people would prefer over the “feel” of either material alone. This would be a preference choice and not a “better worse” choice and only each person can decide on their own preferences.