I have read the article on the Support layer. In memory foam if poly is used a HIGH RESILIENCE SUPPORT OF 2.5 LB and no lower than 2.4lb should be used. The article states you must find the support factor (sagging factor) t be sure. I am a little confused as to what the answer should be. One manufacturer stated they use only HR support under their memory foam with a rating of 24/32. They went on to state their 2.4lb density with a 32 IFD is of such high quality for a supprt layer that other companies would never use it and charge as low as they do for their mattresses. This left me very confused. On their comfort layer the use only 3 lb high density memory foam which did not seem to be of high quality. Where am I going wrong. Is there a formular for HR to be sure of the sagging factor. I am confused about the article I read here.
Hi cinn,
I think you may have misunderstood what you read. HR polyfoam is rarely used in support layers (even polyfoam that is more than 2.4 lbs may not be HR) and it’s not that less than 2.4 lb “shouldn’t” be used in a mattress (you can see the quality/density guidelines I would use in post #4 here) but that if polyfoam is less than 2.4 lbs then it can’t be HR. There are also very durable conventional foams that are higher density than 2.4 lbs that would be very durable choices in a memory foam mattress and since it’s very unlikely that any retailer or manufacturer will be able to tell you the compression modulus of their foam and since it won’t make any difference to you in terms of durability I wouldn’t worry about whether a polyfoam support layer was HR or HD … only that it was likely to be a good match for you in terms of PPP and that it was a good quality and durable material.
If a company does use HR polyfoam or a high performance polyfoam (less than 2.4 lb density but made the same way as HR polyfoam) then it would certainly be a higher quality and more costly material.
I understand your confusion and you aren’t “going wrong”. You have identified the weak link of the mattress you are looking at. I would personally choose a mattress with higher quality comfort layers and lower quality support layers than the other way around because the “weak link” of a mattress is generally in the comfort layers. You can see an example of a similar mattress to what you are describing (very high quality support layer but lower quality comfort layers) and my comments in post #2 here about bedinabox that would apply to other similar mattresses as well.
I would focus much more on the density of a support material rather than whether it was HR or not. The performance advantages of HR polyfoam would be much more noticeable in comfort layers than they would in support layers.
Phoenix