What ILD is memory foam? Trying to replace memory foam layer with comparable latex

Discussions General Mattresses Questions
1

Hi Phoenix and all,

Some background: I’m buying my son a new mattress. He loves the Serta iSeries Flattery Plush (mattress only, full size). It has 1.5 inches of quilted comfort layer, 2 inches of gel memory foam, and 2 inches of HD foam over a wrapped coil base. But I strongly believe a mattress with that much low-quality cush is a body impression waiting to happen. Not to mention that my son is hot sleeper and any memory foam is a poor choice for him.

Following your advice, Phoenix, I sought out a local manufacturer and found Restopedic in Bethany, CT. (BTW: Thank you SO MUCH for the suggestion! I never would’ve thought of it.) I’m having Restopedic clone the Serta mattress, but using layers of latex instead of memory foam. From the bottom up the plan is: a 720 coil Leggett and Platt lura-flex base, a padding layer over the springs, 2 inches of 38 ILD latex, 2 inches of 28 ILD latex (Int’l Latex), and a 1-inch quilted cover of foam, organic wool and organic cotton fabric.

My question is, do those ILDs of latex sound about right to replace the two layers of gel memory foam and HD foam in the Serta bed? I know a little about latex (sleep on a PLB Pamper that I adore), but mixing layers and comparing to memory foam is a bit over my head.

I will follow up on the forum after purchase and delivery, plus price info.

2

Hi lwhughes,

I couldn’t agree more … especially as you said when the quality/density of the comfort materials are low.

I would keep in mind that latex and memory foam are more opposites than similar and that comparing their ILD can be very misleading because of the differences in how they respond and the limitations of ILD testing. For example … memory foam that is in the range of 18 ILD would be considered to be quite firm for memory foam but this would be very soft for latex. The ILD of memory foam also changes with temperature, humidity, and the length of time it is compressed while fast response materials such as latex remain much more consistent under different conditions. There is more about how they compare (or don’t) in post #2 here.

When you are trying to “approximate” two very different designs using different materials that aren’t really comparable … then it’s much more of an “art” than a science and the differences would be subjective more than anything else (see post #9 here). There are too many different types of memory foams and memory foam designs to be able to predict how they would compare for any specific person with any certainty because there is no formula that can compare them in a specific mattress design when there are so many variables and differences between them. In other words … you would be relying on the knowledge and experience of the manufacturer and their understanding of their mattresses and how the components inside them interact together and what you were trying to “approximate” to create a “feel” and PPP that is as close to what you are looking for as possible. This is one of the reasons that dealing with an experienced manufacturer like Restopedic can be so valuable even though you are looking at two very different types of mattress that aren’t really comparable. They would be the best source of guidance because they would be much more familiar with the feel and response of their different designs and how they may compare to the Serta you were testing than anyone else.

Assuming that you go ahead with your purchase … congratulations on your new mattress :slight_smile:

I’m looking forward to finding out about your final decision and of course your feedback once you’ve had the chance to sleep on it.

Phoenix

3

Almost bought the mattress on Saturday, but ran into spec questions. This is the Restopedic mattress I’m looking at:

Restopedic Natures Wonder
720 Lura-Flex, Foam-Encased Coil;
1/2-inch insulator, Dense, gray, rolled material
1.5-inch Medium Soft Hi-Performance Foam

Pillow Top: 2-inch Latex Foam, 2-inch Memory Foam, Euro Pillow Top
20 ILD latex on top. Office manager originally said 28 ILD, but she later confirmed it as 20 so hopefully that is correct.
Memory foam underneath. This is the layer I want to change to 36 ILD latex.

Quilting: 1-inch Hi-Density Foam, 1/2-inch Organic Wool, FR Fabric, Organic Cotton Fabric
Website says 1-inch but office manager said it’s 3/8 inch foam. Kind of unsure which it really is.

Now here’s the thing: it’s chilly in the factory showroom. Like wear a jacket chilly. In fact, the office manager cheerfully admitted that the memory foam beds are like rocks until April. So the memory foam layer under the latex layer was undoubtedly firmer than usual. That’s one reason why I think 36 ILD latex would be a good swap. She also said that a thin layer of latex versus a thick layer of latex can feel very different. So a 2 inch slab of any ILD would feel much softer than the same ILD as a solid 6" core. Is that true? It seems right to me, but I wanted to confirm with you.

My proposed design is, from the bottom up:
Coil, ½ inch insulator, 1.5-inch foam, 2-inch 36 ILD latex, 2-inch 20 ILD latex, foam/wool/cotton quilted layer
I’m fine if the result is a slightly firmer bed that the original design with memory foam.

I originally wanted to semi-clone a Serta iSeries Flattery Plush using latex (and I do understand the degrees to which this is both possible and impossible). So following your previous advice, I asked the factory for a little guidance. They didn’t want to commit to that and said they’ve gotten stuck with the beds when customers didn’t like them. OK, fair enough. They don’t know if I’m a reasonable person or not (I am, I swear!). So I gave up on the Serta idea and will just concentrate on modifying the Nature’s Wonder. But it’s been a challenge. The same office manager who messed up the top layer ILD and possibly mis-quoted the quilting foam, also claimed she couldn’t bring out a slab for us to try or even samples to touch because “that wouldn’t tell us anything.” Of course I know that‘s not entirely true, because I already read a Restopedic review where the customer was able to try the layers. But Restopedic did finally agreed to pull out my layers so I can try them on Saturday. Hopefully I’ll know more then.

So what is your opinion of my layer design? My son is a 6’2", 200-pound, teenager. He likes plush but firm and has dust allergies. I’m trying to dial in a healthy bed and avoid any extremely off-base choices in firmness versus softness. He’s a big kid, do you think the quilted layer plus 2 inches of 20 ILD latex will mean he’s sleeping 3 inches deep in the bed? (I envision it swallowing him). Will a 36 ILD layer beneath that mitigate the sinking in? I’ve never had a pillowtop bed myself, never mind had one built with latex, so I’m at a loss as to how much is too much or not enough, you know? 

Thanks for listening to my saga. BTW: mattress-only price for the Nature’s Wonder is $842 before tax. No charge to swap the memory foam layer for a second latex layer, which I think is super reasonable. And they agreed to free delivery for a nearby town.

4

Hi lwhughes,

[quote]20 ILD latex on top. Office manager originally said 28 ILD, but she later confirmed it as 20 so hopefully that is correct.
Memory foam underneath. This is the layer I want to change to 36 ILD latex.[/quote]

Knowing the ILD of latex isn’t important when you are testing mattresses in person because careful and objective testing will tell you much more than any “comfort specs” such as ILD.

Thickness makes a big difference and it’s effect would depend entirely on what the different thicknesses were on top of. In general a thicker layer will feel softer if it is over something firmer and will feel firmer if it is over something softer (see post #14 here). The thicker the top layer the less the feel and firmness/softness of the layer below it will “come through”. On the floor for example a thicker layer would be much softer than a thinner layer. If the layer underneath is memory foam then all bets are off because it would depend on how much heat is “getting through” to the memory foam, how long you lie on it, and on it’s specific temperature sensitivity and response (each type of memory foam can be different) so there is no way to make meaningful comparisons with a different material that isn’t temperature sensitive outside of “guesswork”.

They are taking a very wise approach because there would be too many unknowns and differences between the two mattresses and the comparison would be much too subjective for any manufacturer to easily agree to that (it could result in a return just because the subjective “feel” wasn’t the same) and it would involve a great deal of guesswork and risk on their part. It’s really not possible to “clone” another mattress using different materials (it’s difficult enough if you are using the same materials).

I agree with them here to a degree as well because unless your son is carefully testing the same layers in the same design and thickness and with the actual cover you would be using then it may be very misleading as well and they may have been a little “gun shy” when you mentioned you were trying to “clone” another mattress using different materials and if you were testing the mattress by “proxy” (I’m not sure if you or your son was doing the testing).

When you get to try the layers on Saturday I would also be aware that a cover can change how they feel and perform for you but I would make sure your son does some very careful testing (for at least 15 minutes after he has fully relaxed) following the testing guidelines and then factor in the effect of the cover so he (and you) would have a better sense of how it may feel when he sleeps on it. I would also be aware that if it isn’t quite right that any changes to the design you tested can have unpredictable results so you are always “safer” testing a mattress that is exactly the same as the one you end up purchasing and then relying on any exchange or fine tuning options as a backup.

I’m happy to comment about the quality of the materials but there are too many unknowns, variables, and personal preferences involved to make any meaningful comments about the design in terms of PPP. Your son’s own personal testing will always be more accurate than any “theory at a distance” (see mattress firmness/comfort levels in post #2 here).

The latex is a good quality material and the springs and insulator wouldn’t be a weak link in the mattress but I would want to know the density of the 1.5" polyfoam layer because in combination with the 3/8" layer of quilting foam it would be a little over the guideline I would tend to use for the total amount of “unknown density” polyfoam (“around an inch or so or less”) in the upper layers of a mattress (this would also depend on weight and weight distribution). Once you are closer to the range of about 2" or more of “unknown density” polyfoam it’s a good precaution to know the density although it’s also a little deeper in the mattress (under the pillowtop and quilting layers) so a lower density material would be more durable in this position.

I don’t know the size you are looking at which makes a big difference in the price or whether it includes a foundation but not surprisingly considering you are dealing with Restopedic this appears to be good value for a mattress of this design (assuming that it’s also a good match in terms of PPP which is the most important part of the “value” of a mattress purchase).

So overall … if you have confirmed the density of the 1.5" polyfoam layer and your son can confirm with careful testing (on layers that are either the same or very similar to the “final design”) that the mattress is a good “match” for him then it would seem to me to be a very good choice.

Phoenix

5

I’ve been curious about that 1.5 inch layer of foam as well. It’s between the spring insulation layer and the upper foam layers. I suppose to protect the foam from wear? I see a seemingly random layer deep down in a mattress (sometimes more than one) and always wondered what the point was. But thanks for the idea, I will ask them about it. The website says HD, but that’s all.

The mattress will be full-sized, no foundation. An excellent price I think, considering the materials.

I think having my son lay on the layers will help a lot even though the cover will change the final feel.

6

Hi lwhughes,

All the layers serve a function that contributes to PPP (Posture and alignment, Pressure relief, and Personal preferences) and how the layers are combined is part of the “art and science” of mattress theory and design. If you were to remove any of the layers or replace them with something different you would have a different mattress. It can be surprising to some people how even an inch of material in some cases can make a significant difference in how a mattress feels and performs. In general terms every mattress will have a support core that is primarily for support and alignment, comfort layers that are primarily for comfort/pressure relief (and also fill in the gaps in the sleeping profile or what I call “secondary support”) and some mattresses also have middle layers in between them which I call transition layers which affect both support/alignment and pressure relief to different degrees. Every layer will affect the feel and performance of the other layers in a mattress to different degrees and in some cases serve multiple purposes.

I also realized I didn’t answer the question in your topic title but the ILD of memory foam is not that relevant because the ILD of memory foam changes with temperature, humidity, and the length of time the memory foam is continuously compressed. ILD testing with memory foam also produces completely different results to the ILD results for fast response foams so for example 18 ILD would feel like firmer memory foam but it would feel soft if it was polyfoam and would feel even softer if it was latex (which is tested for ILD differently from polyfoam).

Using ILD to compare two different types of foam can produce some very misleading and unexpected results.

I would agree that the price and “value” is very good.

Phoenix