Hi Seat15c.
I’ve noticed you duplicated yesterday’s post so I deleted it to keep the conversation focused in one place and ease of reference.
[QUOTE] But the Mattress durability guidelines Says if you have a BMI between
20 and 30 “Polyurethane foam (often called polyfoam): If your mattress is one-sided then I would make sure that the density of any polyfoam is at least 1.8 lb per cubic foot or higher.” [/QUOTE]
I am glad you are asking. Good questions Seat15c! If more people would be as inquisitive as you are, the mattress industry overall would be in a better industry. Great job of identifying any potential weak links and running them by the durability guidelines. Let’s take look and discuss why this mattress, for normal BMI ranges, would not raise any red flags in terms of durability. Here are some more pieces of this puzzle. (Pun intended)
Comfort layers also include any quilting used in the very top part of a mattress since they act together to give a mattress its pressure-relieving qualities. This means that the comfort layer(s) thickness for this mattress is around 4.6" (within the 3" - 6" height range for comfort layers that typically are softer with ower ILD/IFDs).
The general rule is that there should be no more than “about an inch or so” of lower quality/density materials in the comfort and quilting layers combined (around an inch or so would not have a significant effect on the durability or longevity of the mattress). Once you are at about 2" or more of lower quality materials, they are likely to be the weak link of the mattress. You can see this in mentioned in the Mattress comfort layer overview article,
Going back to Nests mattress, it is acceptable to have about “an inch or so” of lower density soft polyfoam in the quilting (in this case 1.5 lbs) without compromising the integrity of the mattress. This uppermost “skin” layer is not under the same laws as the rest of the mattress. The polyfoam in this layer will be gradually breaking in and/or breaking down but it will not affect the spinal alignment. (Spinal alignment can be compromised either by a sagging mattress and/or a mattress being too soft and lacking primary support for a certain sleeper) Additionally, this “skin” atop of a mattress can be quilted tighter or looser (depending on the design) but 1" or 1.5" would not create significant “sag” and any foam breakdown that may occur overtime will mostly contribute to the contouring cradle around the sleeper’s profile.
The next layer of 3" NR Dunlop meets the durability guidelines in all its comfort options.
To quote directly from the Mattress durability guidelines
The next 1" layer of 1.5lb/ft3 transitional polyfoam layer is deeper into the mattress and under a firm latex layer. This layer of 34 ILD would “protect” the transition layer from the mechanical stress the upper layers are under. This transitional layer acts as a buffer between the coils and the latex, preventing possible bottoming on the coils below, especially for higher BMIs. The transition layer may be placed in this particular location within the construction to absorb and dissipate some of the force that is being created by the possible uplift in pressure from the firm coils. This said I would still offer a slight caution in a soft latex layer is used instead of Firm or Medium in the same configuration which may cause the 1" poly transitional layer some wear and tear over time.
I see that you got the spec listing from one of our subscribers, pucknyc, in Post #35 . He posted these specs mid-2020 and I’d keep in mind that companies sometimes rework certain lines which seems to be the case with this mattress (unless pucknyc specs are not accurate). This mattress is now called Owl and the specs appear to be changed. You can find the layering and construction of the Owl | Natural Latex Hybrid and the Owl’s updated specs here on our site. One of the members of our Team corresponded with Nest to update these specs sometime last month.
I hope the info provided above brings some more clarity and helps with understanding the many interconnected variables that are involved in assessing mattress durability.
Phoenix