Ultra Firm Polyurethane; ILD, density, etc.

Great website!
I’m having trouble sorting through all the technical info on Polyurethane Foam. I’m interested in Ultra Firm poly foam as I’m tall and very heavy. You have an immense amount of info on this site, but I would like to ask a few additional questions.
What is the firmest Poly Foam I can buy?
ILD 50? Higher?
5 Lb or Higher is better?
Would thicker be better support for a very heavy person? 6", 8" or more?
My concern is support, not comfort. I’ve never had a mattress that was too firm.
Thanks for the awesome website and great information base!

Hi sixstring,

In theory polyfoam can be made in very high IFD’s that can be over 100 but I took a quick look through the polyfoam suppliers listed in the component post here and the firmest I could see are …

http://www.a1foamandfabrics.com/site/index.cfm Carries 2 lb Everlon that is 90 IFD and 2.7 lb HR foam that is 70 IFD
http://www.foamonline.com/documents/foam-firmness-ild-chart.pdf Carries 2.8 - 3.0 lb HR foam that is 70 IFD
Foam Mattress - Certified Healthy Mattresses Carries 3.2 lb Everflex that is 70 IFD

These are all ultra firm foams that would be more suitable for seat cushions than for mattresses.

You won’t normally find polyfoam in a 5 lb density outside of memory foams (that would all be too soft) and some specialty foams that also probably wouldn’t be firm enough for you (see post #2 here). Once you are past about 2.2 lbs - 2.5 lb density or so then the relative durability benefits of higher densities would be diminished.

This is one of those questions that has many “it depends” in the answer.

The thickness of a mattress is just a side effect of the design and by itself isn’t particularly meaningful because whether a thicker or thinner mattress would be better or worse for any particular person will depend on the specifics of the material (type, firmness etc) and on the other layers in the mattress. Thickness is only one of many specs that are used to make different mattresses that perform and feel differently and that makes a mattress suitable for one person and not another. There is more about the effect of thickness in post #14 here and more about the different specs that can affect the softness/firmness and pressure relief of a mattress in post #4 here and there is also more about some of the specs that combine together to affect the feel and performance of a mattress overall in post #2 here. Regardless of how thick or thin a mattress may be … the most important part of the “value” of a mattress is how suitable it is “as a whole” for your particular body type, sleeping positions, and preferences in terms of PPP (Posture and alignment, Pressure relief, and PErsonal preferences) regardless of how thick it may be.

There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.


Sorry, I got so engrossed in the research I forgot to thank you for your generous reply.

Thank you very much!