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Coils versus foam support layer? 02 Jun 2017 09:37 #1

  • hdolstra
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I have read all the tutorials and have taken copious notes. About to pull the trigger on a Kiss Mattress but am hesitating over the issue of a foam support core versus a pocket coil core. I know this is all a matter of personal preference, but is there a body of customer feedback on one mode versus the other?

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Coils versus foam support layer? 02 Jun 2017 10:32 #2

I have read all the tutorials and have taken copious notes. About to pull the trigger on a Kiss Mattress but am hesitating over the issue of a foam support core versus a pocket coil core. I know this is all a matter of personal preference, but is there a body of customer feedback on one mode versus the other?

I've been wondering the same thing. I'm aware of two stereotypes with respect to innerspring mattresses: (i) the springs create pressure points and (ii) you can "feel" the springs through the mattress. But when the mattress has foam in the comfort layer, I suspect that these stereotypes are false. I do wonder about durability and comfort over time though. All else being equal, which kind of mattress is likely to keep feeling comfortable into the future? For example, I imagine that as the foam in the comfort layer of a foam core mattress begins to break down, the mattress will feel less comfortable, but there won't be any springs to create pressure points.

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Last edit: by zab.

Coils versus foam support layer? 02 Jun 2017 13:20 #3

  • phoenix
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Hi hdolstra,

Welcome to the Mattress Forum! :)

am hesitating over the issue of a foam support core versus a pocket coil core. I know this is all a matter of personal preference, but is there a body of customer feedback on one mode versus the other?

The first thing I would address is the unreliability of customer feedback.

While other people's comments about the knowledge and service of a particular business can certainly be very helpful ... I would always keep in mind that you are the only one that can feel what you feel on a mattress and I would be cautious about using anyone else's suggestions, experiences or reviews on a specific mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you. In many if not most cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person or even a larger group of people in terms of comfort, firmness, and PPP may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range). In other words ... reviews or other people's experiences in general won't tell you much if anything about the suitability, quality, durability, or "value" of a mattress for any particular person (see post #13 here ).

While surveys or reviews can certainly be interesting, they can also be quite misleading because they take very broad based and non specific information that doesn't take any details and specifics into account so you end up with "muddied averages". Even with mattresses that use the same materials and the same types of foam there is a huge difference between different types of mattress designs that use different layering combinations or different thicknesses of the same material and some people may love one model and hate another one even though they would even be in the same "subcategory".

The same would be true for every mattress category. There are many different types of polyfoam core mattresses for example that each have a different "feel" and there are also thousands of different designs of polyfoam core mattresses and it's very common that someone may try one and hate it and then try another that uses different types of polyfoam for the core or has a different design or firmness level and love it because it's completely different.

Innerspring mattresses have even more variety because they are so common in the industry and there are so many different types of pocketed coil innerspring that each have different properties and response curves along with thousands of different types of padding materials that are used over each type of pocketed coil innerspring that once again someone may try one pocketed coil innerspring mattress and hate it and yet when they try one that has a completely different design or type of pocketed coil innerspring or padding materials they may love it.

Another one of the risks of using this type of information as a basis for choosing a mattress is that people are also very different and if you choose a mattress based on the premise that "many people seem to like this type of mattress so I will probably like it as well" it can create unrealistic expectations because any individual (and for that matter most individuals) may be very different from the "average" of a group in terms of their body type, sleeping positions, and preferences and there is no way to know whether the specific mattress they are considering was even included in the group or has any weight in the results. I would caution anyone to take a very skeptical approach in using this type of information when they are looking for a mattress that is likely to be the best choice for them on an individual basis.

If you have a pocket coil as the support system in one mattress and high quality polyfoam as the support system in the other and both of them used the same type, thickness, and density of memory foam (for example) in the comfort layers then they would be very comparable in terms of durability and would have some strong similarities in terms of "feel" because they would have the same comfort layers but some of the "feel" of the pocket coil would "come through" the memory foam and it would be more "springy" and responsive than the memory foam mattress that used polyfoam as the support core. If you had a pocket coil mattress that used a different material in the comfort layers (such as polyfoam or latex) and compared it to a typical memory foam mattress, then how the different comfort materials would compare would have the most significant impact on how the mattresses compared as a whole, both in terms of "feel" and in terms of durability.

The choice between the two support cores is a personal preference but I would also keep in mind that the upper layers of a mattress are usually the weak link of a mattress (a mattress will tend to soften and break down from the top down) so it's always most important to make sure that no matter what materials you prefer in the support core of a mattress, that your comfort layers are higher quality versions of that type of material so that your mattress has less chance of softening or breaking down prematurely which can result in the loss of comfort and support and the need to replace the mattress (and foam softening and the loss of comfort and support isn't covered by a warranty).

There are hundreds of different types of pocketed coil innersprings with different firmness levels that are used in combination with hundreds of different combinations of materials on top of them so there isn't a single "feel" for innerspring mattresses that you can use to compare them to other mattresses. The same is true for mattresses that use polyfoam support cores so the only way to know how two mattresses compare and the differences you would feel between them would be based on your own personal experience, but in very general terms an innerspring support core will have more "bounce" and "springiness" than polyfoam which will be less "lively" and responsive.

Polyfoam is less resilient and responsive and somewhat "stiffer" and less "springy" or "bouncy" than an innerspring, but it can also make a good support system for those that are also a little more restricted in terms of their budget or for those that prefer how it feels over other types of support materials or components. Both innersprings and polyfoam cores can be durable support unit choices. Some of the most knowledgeable people I know in the industry that could sleep on anything they wish to, sleep on innerspring/latex hybrids (often a pocket coil) but of course others sleep on all latex or memory foam mattresses and when you are looking at high quality materials it really is a preference choice.

There are an almost infinite number of variations in innersprings that each create very different types of performance and interactive qualities of a particular mattress. These include the number of coils, the turns of the coil, the height of the coil, the gauge of the coil, and the different methods of joining the coils together. Different shapes also make a big difference (giving a multiple compression rates rather than the more linear compression rate or "spring rate" of a cylindrical coil). There are also "coil in coil" versions (which function in "parallel" in terms of how they compress which adds firmness when the coils compress together) and coil on coil (which function in "series" in terms of how they compress and adds "travel distance" to each coil). There are also many variations of insulator layers or flexolator layers and zoning layers that can be used on top of a coil in addition to coil zoning itself which can alter their properties significantly.

There is a technical spec for foam which is called compression modulus which is the ratio between the force needed to compress a foam to 25% and the force needed to compress the same layer to 65% of it's thickness. 65% is exactly 2.6 times 25% which means that a completely linear compression rate would have a compression modulus of 2.6. High resilience polyfoam (2.5 lb) has a compression modulus of 2.4 or above.

Most springs have a softer section and a firmer section (which can be achieved with different shapes such as thinner and thicker diameters in parts of the spring or different gauge springs on top of each other and in other ways as well). This means that this type of spring would have multiple spring rates.

In addition to this ...all foams have a quality called "hysteresis" which is the ability to absorb energy. Latex has a hysteresis of around 20% to 30% which is the amount of energy absorbed. HR polyfoam is a bit lower. Innersprings retain almost all their energy and so will "bounce back" or "push back" much more strongly but this is also affected by the type of materials that are used over the innerspring. The "opposite" of hysteresis is resilience which is the height of the rebound a material gives when a ball is dropped on it expressed as a percentage. Innersprings have a higher resilience than polyfoam. This means that an innerspring mattress will be more "springy" than other foams and those who have tried both will validate that the feel between them and how they each react to motion is very different. Some prefer one while other prefer the other. Both can make high quality support layers.

Finally there is a property called "point elasticity" which is the ability of a material to compress without affecting the areas beside it. Polyfoam can have a decent point elasticity which means it can take on the shape and profile of a body (but not as good as latex). Because of it's elasticity ... there are millions of points that can compress individually and which only affect small areas around it. Innersprings on the other hand have less "point elasticity". Their ability to take on a body shape and isolate motion is more limited to the number of coils and how the coils are connected to each other. Pocket coils with a high coil count would be the most "point elastic" of the innerspring types.

All of this can also be modified by the layers both above and below a particular component or material.

There are other differences as well that are connected to the nature of foam (things like "creep", airflow and temperature regulation and many others) but in terms of performance these are the general differences.

There are so many differences between them that it is really impossible to answer these types of "apples to oranges" questions in any other way than through very general comparisons that may not represent the differences between two specific mattresses.

In essence ... all mattresses boil down to what I call PPP which is their Pressure relieving qualities (that comes from the pressure relieving cradle that they form which spreads weight out over the mattress surface), the Posture and alignment qualities (this is the ability of a mattress to "allow" your wider lighter areas like shoulders to sink in enough while "stopping" the heavier narrower areas like the pelvis from sinking in too far) which keeps your spine in alignment in all your sleeping positions, and the Preference qualities (which are things that are more subjective or preference based like springiness, energy absorption, breathability, being more "on" or "in" the mattress, the surface or "hand" feel of the mattress, motion isolation, slower or faster response, and others).

So there are many complex differences even within each category much less the differences between an innerspring and a polyfoam support layer that the best way to decide is to make sure that they both provide the pressure relief and alignment you need and then everything else after that is preference and the relative "value" of each material compared to the price of the mattress.

There's more about the different types of spring support units here , and polyfoam support cores here .

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