I emailed the 4sleep people and they responded within 30 minutes! Here are the details:
[color=#0000bb]We make the mattress with four layers specially designed to provide the proper support without experiencing pain from pressure points. It’s a tricky science to figure out the right combination and there is a lot of misinformation out there about IFD’s and densities and how those translate into softness or firmness.
Our four layers are:
1.5" of 3.5lb density ThermaSense Memory foam with an IFD of 10. This is a very special type of gel foam that differs from the normal gel memory foams in that it not only absorbs heat from your body but also can liberate heat back to the spots where you need it. The goal is to maintain the optimal temperature for restful, deep sleep and our ThermaSense foam can do that. We don’t use an overly dense foam so that you will achieve that floating sense that is so unique to memory foam: float but no sink.
The second layer and third layers are made up of a special foam that provides an alternative bridge between latex & visco memory foam: you get the comfort & conforming properites of visco but it is extremely compression resistant so you do not sink, you have better support as you “float” on top of the layers. This foam also has superior air flow for great heat dissipation to aide in cooler night sleep, i.e. it continues to pull air through from the top layers. The second layer is 3.0lb density with a 10 IFD, the third layer is 3.0 lb 18 IFD.
The core layer has a 35 IFD, the side rails are 50 IFD.
While we are happy to provide the technical specs on our mattress, they do not alone tell the whole story. The unique and specially formulated cell stuctures, composition and properties of each layer very much affect the overall “feel.” The order in which the layers are assembled is a science in and of itself. If you have to go with a standard firmess scale we’d rate ourselves about a 6.5 to 7 out of 10, with 10 being the firmest. But because of our ThermaSense top layer, you’ll get that plush feel without losing any support. And because of the two middle layers, you’ll never feel like you’re sinking in quicksand, can’t move in your bed, or that your sleeping partner is bouncing you around all night. However, you’ll get plenty of localized bounce to support your own movements when and where you need it. J
We spent many years compiling information from our customers and competitors mattresses to determine what makes a truly great mattress. We feel we’ve accomplished that with a caveat: we’re always open to change as the needs of our customers change. That’s why we feel the trial periods our important, not just for the customer but also for us to learn how people truly adjust to the foam and what makes them the most comfortable.
Of course we offer a full 20 year warranty, our foam is 100% USA Made and CertiPur-US certified. We use plant-based derivatives in our foam so that it is naturally antimicrobial, hypoallergenic, dust mite and mold resistant. Contrary to what some competitors are saying about layers in a mattress being bad for air flow, we use water based glues applied in a way that minimizes blocking of air flow through the entire mattress and allows each layer to enhance the overall support, durability and comfort of the 4Sleep mattress.[/color]