Hi Jmoss,
Thank you so much for the information. I was skeptical of the density information about the Spa Sensations as it didn’t seem to be in line with other Zinus brands and I am thankful that you took the time to do the research.
I am somewhat adverse to ordering a memory foam mattress online without a great return policy for several reasons.
Memory foam itself has a basic “set” of chemicals and method of manufacturing that is used but there are hundreds of variations between manufacturers and even the same foam manufacturer will often have dozens of variants and custom formulations which can change the recovery time, the breathability and heat retention, heat sensitivity, and many other characteristics of their memory foam, even when similar densities are compared. The support layers and the ticking/quilting can also make a huge difference in how the memory foam “performs”. This means that memory foam comparisons between different manufacturers, even of the same density, is not as easy to “translate” as latex (which has much more similarity in its characteristics between different manufacturers than memory foam) or even polyfoam.
So in many cases … buying a “standardized” memory foam mattress online regardless of the density or quality of the memory foam itself can be a roll of the dice. Very few people who are looking for a memory foam mattress truly realize how different they can be and how many factors can change the feel and performance of the mattress they are considering. Since memory foam, in general, is pressure relieving … the biggest variables are in the support, feel, and heat retention of the memory foam mattress and of course in its durability (and in the case of unknown foams … harmful chemicals and VOC emissions).
The thickness of the memory foam layer and the type of layers under it can play a major role in alignment regardless of the quality of the memory foam itself. Memory foam in very low densities are also not as “gradual” in their response and so can be much firmer when cold and then melt more easily when warmed up and become too “soft” and a person may “go through” the memory foam onto the firmer layers underneath which can cause pressure issues in spite of the memory foam. Of course, they are also not as durable. Lower density memory foams may also be more breathable because the internal structure is not as dense and “insulating”. There are also many other factors involved with heat retention of a memory foam, however.
Memory foam and viscoelastic materials also have a characteristic called “creep” which means that over time … they become softer (lose some of their resistance to pressure) in addition to the variables of heat, pressure, and humidity. This means that someone who may be in alignment at the start of the night may sink deeper over the course of the night and lose alignment … even if the heat and humidity don’t change.
For all these reasons … and more … I believe it is much more “accurate” to purchase a memory foam mattress through personal testing rather than buying online … at least without a great return policy. If someone can test a memory foam mattress locally with a known type of foam and then that same construction and foam is available online … then, of course, the risk of getting it wrong is much lower. Overall local manufacturers or smaller sleep shops are usually a much better way to go when that is possible and the value is similar.
I did talk with Rocky Mountain Mattress yesterday about their memory foam mattresses. They sell Bayer memory foam on their main pages (which is a large foam manufacturer but not listed on Certi-Pur) but they also have a selection of Foamex memory foam (which he actually prefers as well). The Foamex are layered DIY constructions and the support layers can be customized much like many latex DIY mattresses that some of the members here sell. They may be worth considering. Their Foamex mattresses are here http://www.rockymountainmattress.com/specials-c-28.html . They also have some good youtube short clips showing the different responses of different memory foams.
FWIW … Sensus is a slower recovery foam than Aerus (both are Foamex) and less breathable but “denser feeling” or “firmer” than the Aerus although I use firm here only relative to other memory foams as no memory foam is really firm unless it is cold.
I will list more as I come across them or do a little more research on many I already know about for those who may be looking to buy memory foam online in spite of the “risk” of doing so.
Information about the basic functions of a mattress (pressure relief and spinal alignment) is here Five steps to your perfect mattress - Support and Alignment - The Mattress Underground. General information about testing for pressure relief and alignment (and the other steps to finding your perfect mattress) is here Five steps to your perfect mattress - Overview - The Mattress Underground and more details about pressure relief testing are here Five steps to your perfect mattress - Pressure Relief - The Mattress Underground and spinal alignment testing here Five steps to your perfect mattress - Support and Alignment - The Mattress Underground
Phoenix