Differential and Progressive, Support Factor, HD vs. HR


I pray I don’t make this too long. I just don’t have the time or energy to over-elaborate, right now. Sorry if it seems like I am being overly simplistic or focusing too much on this or that spec etc… I just have a couple of questions regarding some (very enlightening) reading I have been doing on this site.
Differential vs Progressive
Diff and progressive design: I read your overview etc… on these and also read you telling another member that these are merely guidelines and not concrete designs that you would, for example, see a manufacturer list as a feature or spec. I’m not saying this right… let’s just say I understand what you were telling that member. My question is; Are these actually mattress designs that are black and white/this or that, or can one person’s differential be another’s progressive based on their weight, body type etc…
If one person of 100lbs lays on a mattress that has 3" of say, 4lb MF and never “sinks in” to the support layer, would this make the mattress a Differential design, as opposed to another at 200lbs laying on the same mattress and sinking well past the comfort layer and “borrowing” from the support layer(s). Does the same mattress essentially become a progressive? I am well aware of my “theory at a distance” problem, I’m just wondering if I have these definitions and their grey areas in perspective. The main thing I got from that article, in combination with others is that with memory or any other comfort layer, more is not better and just enough is the goal. Also, that memory foam has characteristics of air(low resilience?) And that is why too of thick layers of it causes lumbar support issues(my biggest complaint with beds)

This is why my Tuft n Needle + blind topper purchase has some problems, and ordering both at the same time would be unwise at best. The other problem is that most toppers are not returnable…

Support Factor/Sag Factor
Is support factor a spec that I should ask for when speaking to manufacturers? To what extent can it become a weak link? Or a “feature?” If I see a support layer labeled as HR foam, the manufacturer should be giving me a Support/sag factor of 2.5, otherwise it is mislabeled, correct?

Rocky Mountain Mattress (I think is one of your members), for example, boasts a 2.4 support factor in their support layers. Does this indicate HR Foam? I think you said HR must be 2.5. Is it safe to say they are using very high resilience HD Poly? Is that .1 A hard line between the two, or are these two products as close as they are on paper(an HD w/2…4 SF and an HR with 2.5 SF)?

I get the impression that you don’t consider HD Polyfoam a very ideal support material, at least in terms of durability. Unfortunately, it would seem that 90% of foam support layers are made of it, including those made by many of the member companies on MU. Is this simply a price trade-off that one has to make? If true HR foam is less expensive than latex, but more expensive than coils, why don’t we see more options using it? Is it just too close to latex’s price point to be relevant? Is it not worth it to them inject another price point/option between HD Poly and Latex, considering most consumers have not been enlightened by the MU? :wink:

Hi plasticpitchfork,

I think you may be paying too much attention to specs that will have no meaning to you in real life. Post #13 here has more about the most important parts of the “value” of a mattress purchase and when you get overinvolved with this type of “theory” and analysis you will end up at the beginning of a learning curve that can take years before you will be ready to buy a mattress only to find it will make little difference anyway.

You can see my thoughts about the importance of knowing whether a mattress is closer to a progressive and differential design in post #2 here. These are only generic descriptions that can be used as to help understand some basic concepts of mattress design but it’s really not important which one a mattress is closest to as long as it’s a good match for you in terms of PPP. One isn’t any “better” than the other.

In a word no … it’s not something that you need to ask about. Many manufacturers may not even know what it is (although some would) and it’s certainly not a spec that would be important to know. It has no relationship to any weak link in a mattress. It’s not the type of information you will need unless you are a mattress designer and even then it would only be one of many other specs that could be part of choosing the materials and components in a mattress design. In many cases a mattress manufacturer will label their polyfoam as HR if the rep from their foam supplier calls it HR … whether it is technically correct or not. You may also see some HD polyfoam that is higher density than some HR polyfoam because not all polyfoam that is more than 2.5 lbs density is HR and you will often see polyfoam that is lower density than 2.5 lbs that is labeled HR (which would be more correctly called high performance or high comfort foam). I would stick to the basics.

I’m not sure where you read this because it’s certainly not the case and I think it can be a very good support layer and can be very durable in higher densities (see the guidelines here).

They are one of the members here yes (the membership list is here). Density, compression modulus, and resilience are part of the technical specifications for HR polyfoam (see page 4 here) but these are used quite loosely in the industry. To be accurately labeled as HR polyfoam it would need to have a 2.5 lb or higher density, a compression modulus (support factor) of 2.4 or higher, and a resliency of 60%. If a polyfoam has all three then it would be technically correct to call it HR.

In the end … most of the information you are “studying” will more likely lead to paralysis by analysis and information overload than it will help you choose a more suitable, a more durable, or better “value” mattress.


Thanks again,

I have bought 2 mattresses in my life, both times, I test drove them, along with several others. I regretted both.

I got the impression when reading the description of the different kinds of cores, especially Poly cores.

The “Too much memory foam” and the non resilient properties of such foam was very helpful. It then raised some curiosities. I am glad I understand push back.

I just wish there was a baseline to start from based on my body height, weight, sleeping positions, and previous issues with mattresses. At least in a broad sense for each type of mattress, and in terms of alignment/support only. Even considering how hard it can be to compare apples to apples.

Hi plasticpitchfork,

Unfortunately there isn’t because there are just too many unknowns, variables, and personal preferences involved in choosing a mattress that can make each person unique and very different from someone else … even if they have the same general body type.

The only two ways to choose a mattress are either careful and objective testing using the testing guidelines in the tutorial post (which are different from just testing a mattress for “subjective comfort” which can have lower odds of success than random chance alone) along with the guidance of a knowledgeable and experienced salesperson that has your best interests at heart or if you can’t test a mattress in person then a more detailed conversation with a knowledgeable and experienced online manufacturer or retailer that can help “talk you through” which of the options they have available would have the best chance of being suitable for you based on the averages of their customers.

If you don’t have confidence in the choice you are making (either locally based on your testing or online based on a more detailed conversation) then the options you have after a purchase to fine tune the mattress or exchange or return it would become a more important part of your personal value equation and the “value” of your purchase so that you can lower the risk of making a choice that isn’t suitable for you and use your actual sleeping experience to confirm whether a mattress is a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).

Based on the information in your previous posts and some of the “challenges” you are facing in choosing a mattress … I would start with a visit to Quality Sleep / My Green Mattress and then go from there. If nothing else you will be much better informed about the types of mattresses that will likely be most suitable for you and you will have a good baseline that you can use to compare other mattresses.