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I have searched the forums without much luck, so I am posting my question here. About a year ago we purchased a split king from SleepEZ. My side has a Talalay soft layer and Dunlop medium and firm layers. When I sleep on the mattress my mid to upper back gets so painful that it wakes me in the night and it tends to be painful the entire next day. I have tried all possible combinations and permutations of the layers with little relief. (I have the same problem on my wifes side of the bed) I have tried thick pillows, soft pillows, two pillows etc. I have also tried different toppers I do tend to end up on my side, occasionally on my stomach... I sleep fine on the guest room traditional mattress or in a recliner. We are going to have to get rid of the bed if we cannot come up with a solution... Any thoughts? Thanks jms This message was modified Feb 26, 2010 by jms969
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Phoenix wrote: "I think latex is the issue" Not so much the material itself but the support it gives in the softer ILD's very well could be. An HR poly foam with the same qualities (ILD and support ratio) would have the same issues. From everything I know and based on the people I've talked to that know a lot more than me, back issues have very little to do with firmness or softness per se ... even though it's a common misperception. It has much more to do with how well the back is aligned when you are sleeping and misalignment ... and back issues ... can happen with any firmness of mattress. The days of "firmer is better" are long over ... thank goodness lol I'm glad you sold your mattress ... and good luck with your next one! Phoenix |
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It's actually not the density of foam that determines it's support but it's ILD and support ratio (the ratio of the weights required to compress foam to 25% and 75% of it's height). The ild is how much weight it takes to compress the foam down 25% so if a foam had an ild of 20 and a support ratio of 3 that means it would take 20 lbs to compress a 4" piece of foam down to 3" and it would take 60 lbs to compress it down to 1". For example memory foam has a typical density of 5.3 lbs / sq ft and yet has almost no support (very low support ratio). Some of the HR foams out now have a density of say 2.1 (there's quite a range but 1.8 - 2.5 are typically used as a bottom layer in a mattress) and yet they offer very firm levels of support. Jello is denser than styrofoam but has little support. Some of the newer foams are quite light (not very dense) compared to latex and memory foam and yet have very high support levels. So if you were to take a piece of say energia foam with properties (ild and support ratio) the same as a piece of latex, the back issues would be the same, even if the densities were different. In other words they would feel identical and offer the same level of support. Phoenix This message was modified Oct 11, 2010 by Phoenix
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Phoenix wrote: It's actually not the density of foam that determines it's support but it's ILD and support factor (the ratio of the weights required to compress foam to 25% and 75% of it's height). The ild is how much weight it takes to compress the foam down 25% so if a foam had an ild of 20 and a support factor of 3 that means it would take 20 lbs to compress a 4" piece of foam down to 3" and it would take 60 lbs to compress it down to 1" For example memory foam has a typical density of 5.3 lbs / sq ft and yet has almost no support (very low support factor). Some of the HR foams out now have a density of say 2.1 (there's quite a range but 1.8 - 2.5 are typically used as a bottom layer in a mattress) and yet they offer very firm levels of support. Jello is denser than styrofoam but has little support. Some of the newer foams are quite light (not very dense) compared to latex and memory foam and yet have very high support levels. So if you were to take a piece of say energia foam with properties (ild and support ratio) similar to latex, the back issues would be the same, even if the densities were different. Phoenix
When I say density I am not refering to jello or styrofoam, I am speaking in context of latex foam...
Anyway no longer matters, we are rid of the mattress, took a bath on it and learned a very valuable lesson!!! |
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Compressability is exactly what support ratio is and is exactly what I suspected the problem was when I first started posting to this thread. Latex in lower ild's has a higher support ratio than the typical pillow top which as I said earlier fit your symptoms of being able to sleep on both harder surfaces and pillowtops without problems. If we had confirmed this by checking to see if your back issues didn't happen on a very firm latex, then it would have been relatively easy to solve the problem ... either with zoning as sandman mentioned, different thicknesses and ordering of foam, or different foam types. Even a 2 zone solution which would have involved ordering less than half a layer of foam would probably have worked really well. In any case, I'm glad you're half way to solving your back pain issues. Back pain is never fun no matter what the cause. Phoenix This message was modified Oct 11, 2010 by Phoenix
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Phoenix wrote: Compressability is exactly what support ratio is and is exactly what I suspected the problem was when I first started posting to this thread. Latex in lower ild's has a higher support ratio than the typical pillow top which as I said earlier fit your symptoms of being able to sleep on both harder surfaces and pillowtops without problems. If we had confirmed this by checking to see if your back issues didn't happen on a very firm latex, then it would have been relatively easy to solve the problem ... either with zoning as sandman mentioned, different thicknesses and ordering of foam, or different foam types. Even a 2 zone solution which would have involved ordering less than half a layer of foam would probably have worked really well. In any case, I'm glad you're half way to solving your back pain issues. Back pain is never fun no matter what the cause. Phoenix To answer your questions again I tried very firm latex I tried very firm latex with a 3 inch topper I tried very soft latex There are 120 permutation of these 6 slabs of latex in a 3 layer subset. Plus the various permutations of toppers (latex, fiber, memory foam) I had the same back problems with all configurations, there is no "easy" solution to this problem I spend 18 months trying all of the compunations and permutations. I refuse at this point to spend anymore money on a problem with a suboptimal solution (or better yet unsolvable). This message was modified Oct 12, 2010 by jms969
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sandman wrote: Sounds like what you really need is some zoning. Perhaps Flobeds would sell you half of a vzone layer that has been returned. This way you can customize what is under your hips (and other areas) vs. what is under the shoulders. Softer under shoulders, firmer under hips (or whatever works!). Or, possibly you could cut out a part of one of the firmer pieces under the shoulder areas and put in a softer piece of latex (or other foam). Maybe buy a 1" soft twin piece and cut it up to the right sizes to fit The vzone has a soft piece from about 13" from the top of the bed down to about 23". So, 1 soft 10" x half width of mattress x depth of latex layer (3"?) would do. You could probalby have the soft layer all the way from the top down 23", because I don't think what is under the head matters that much I actually have done this, in my bottom 32ILD layer. Right now I have so much foam over it tha it may not make much difference, but near the top it could make a significant difference. |
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Phoenix wrote: It's actually not the density of foam that determines it's support but it's ILD and support ratio (the ratio of the weights required to compress foam to 25% and 75% of it's height). The ild is how much weight it takes to compress the foam down 25% so if a foam had an ild of 20 and a support ratio of 3 that means it would take 20 lbs to compress a 4" piece of foam down to 3" and it would take 60 lbs to compress it down to 1". For example memory foam has a typical density of 5.3 lbs / sq ft and yet has almost no support (very low support ratio). Some of the HR foams out now have a density of say 2.1 (there's quite a range but 1.8 - 2.5 are typically used as a bottom layer in a mattress) and yet they offer very firm levels of support. Jello is denser than styrofoam but has little support. Some of the newer foams are quite light (not very dense) compared to latex and memory foam and yet have very high support levels.
So if you were to take a piece of say energia foam with properties (ild and support ratio) the same as a piece of latex, the back issues would be the same, even if the densities were different. In other words they would feel identical and offer the same level of support. Phoenix Where did you learn so much about the foam/mattress industry? |
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Density can be a measure of durability (longevity) ... but only if you are comparing the same material. 3 lb memory foam will usually not usually last as long as 5 lb memory foam (of the same type). 1.8 lb HD foam will not last as long as 2.5 lb HD foam (again of the same type). Notice here that anything in a poly foam above 1.8 is usually called HD (High Density) while in other foams (memory foam for example) this would be ridiculously low. HR foam means high resiliency which means it can be compressed and come back more readily and more often (not as prone to holding an impression). It is generally considered to be the best of the poly foams. There is a lot of research going on to make HR foam with qualities and durability that mimics other foams (latex for example) or that has certain desireable qualities. Also ... if you are comparing the same materials, a higher density will have a higher ILD (measuring the initial weight it takes to compress a foam down 25%). Typically these measurements are done on a piece of foam 4" thick and at least 20" x 20" and the force is applied with a round 50 sq in deflector foot. Different foam thicknesses, sizes, and percentage compressions as well as many other factors will lead to different numbers so this is the "sort of" standard but it is not completely definitive. A really great discussion of this and the huge number of variables that can be involved in ILD (for those so inclined) is here (the pfa or polyurethane foam association is a great resource) http://www.pfa.org/jifsg/jifsgs4.html ILD and IFD are the same thing with a different name. Support factor (also called support ratio or compression modulus or comfort factor) is discussed here http://www.pfa.org/intouch/new_pdf/lr_IntouchV3.1.pdf I'm glad you asked this too because I just realized that the support factor is a ratio between 65% and 25% and not 75% and 25% as I have been saying earlier. There are some sites that talk about it as 75/25 but the pfa is the "authority" so I have learned something today that I never noticed before lol.
Anyway back to your question, when you are comparing different materials, density does not have nearly as much value and really doesn't say much at all about either comfort or support. For example a 3 lb HR foam will usually last for a very long time and is considered very dense and firm while a 3 lb memory foam will usually wear out (or lose it's properties) much more quickly and is considered very soft. Both memory foam and latex are common in around the 5 lb range and yet the latex is much longer lasting and offers much more support. So density only really says how much a cubic foot of material weighs and little about the qualities of the material itself.
Density is only really good as an indication of the relative durability and longevity (and in most cases firmness) of 2 pieces of foam of the same material
As to your last question ... When I'm interested in something I read a LOT. I tend to be a "researcher" by nature and enjoy the challenge of getting to the bottom of things. Sometimes getting to the bottom means falling into a never ending pit though (laughing). Phoenix This message was modified Oct 12, 2010 by Phoenix
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Thanks for the info. Within the PU family, it does look like support factor is positively correlated with density. That makes sense. Do you have a reference chart that shows support factors for a lot of different types of foam? Latex vs. various PU vs. memory foam etc.? Of course it will vary from product to product, manufacture to manufacturer, etc. But would be nice to have a general guide. |
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I sure wish I did but I've never found one. Support factor doesn't seem to be discussed as much and while there are quite a few places that talk about the ILD of different foams, support factor information, as important as it is, is a lot harder to come by. I think that the foam manufacturers (and bed manufacturers as well) often keep crucial information to themselves or tend to talk about their foams in more general ways in an effort to delay others from duplicating it. I'm still looking and in the end may have to put my own chart together from many little pieces. Phoenix |