I’m planning to buy a 3 inches topper to use it below my futon. I want it to be very firm. First I was planning to go for the latex option but I now I want to buy cheaper (foam option). Now the problem is that the “extra firm” foam topper provides 1-4/9 pounds of density per cubic foot and the “firm” latex topper provides a 5.9 pounds of density per cubic foot. That’s a big difference. So just by curiosity I verify the “soft” latex topper and it’s a 4 pounds of density per cubic foot. So there must be something wrong. Is really the “soft” latex topper more than 3 times firmer than an “extra firm” pure foam topper? Please help. Thanks!
Density comparisons between different types of foam materials (polyfoam, memory foam, or latex foam) aren’t particularly meaningful or useful because each type of foam material comes in very different density ranges that can’t be compared to each other and the effect of density is different with each type of material.
With polyfoam … density is a “quality spec” and has little to nothing to do with the firmness of the foam. The density of polyfoam is the single most important factor in its durability but any density of polyfoam can be made in a wide range of firmness levels so you could have low density firm polyfoam or soft polyfoam or higher density firm polyfoam or soft polyfoam. The specs that will have the biggest effect on the firmness of a polyfoam layer are the ILD/IFD of the foam (which would be the “simplest” method of comparison), the compression modulus of the foam, and the thickness of the foam.
Latex on the other hand is very different and with latex density is a “comfort spec” which has a direct effect on the firmness/softness of the latex. Even here though density comparisons aren’t meaningful if you are comparing different types and blends of latex and are only useful if you are comparing the same type and blend of latex. Talalay latex will tend to have a lower density than Dunlop in the same firmness level and synthetic latex will also tend to have a lower density at the same firmness level than natural latex. If you are comparing the same type and blend of latex then higher densities will be firmer (see post #6 here).
Excellent explanation as always. Now that you mention that this is a quality spec for for the polyfoam would you say tha a 1-4/9 pounds of density per cubic foot polyfoam is high quality or just average?
This would be the equivalent of 1.44 lb density which would be towards the lower end of the polyfoam density range. There is more about polyfoam density in this article and in the foam quality/density guidelines here.
Thank you phenix. I’ve been looking all this time for a 2.0 lbs to 2.5 lbs and 3" thickness very firm polyfoam and there is nothing around the web. Can you help me out. Thanks a lot!
The component list here includes the better online sources for polyfoam that I’m aware of. There are also some comments about their relative prices in post #4 here and post #6 here.