Putting the layers together - Overview
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We have talked in previous sections about the role of the support and comfort layers and the different materials that can be used in each. In this section we will talk about the 3 main ways of putting them together and about the remaining layers that will not only complete your mattress but can have a significant effect on how it performs and feels.
This method uses thicker/softer comfort layers over firmer support layers. It is called "differential" because there is usually a big difference between the softness of the comfort layers and the firmness of the support layers. There is also a clear "split" between the roles of each layer as the comfort layers provide almost all of the pressure relief and supports the lumbar area and the support layer is focused on preventing the heavier parts of you from sinking in too far. While there may be a middle layer in this construction, it will be closer to the bottom layer in firmness as this construction is basically softer over firmer.
The main benefit of this construction is that it is easier to “get right”. Because the comfort layers are doing most of the work in filling in and supporting the “gaps” in the body, it is generally best to limit your comfort layer choices to materials that are more resilient to support the lumbar area and that also have the ability to shape themselves to the contour of your profile. Both of these qualities are important in the comfort layer of this type of construction. Because the support layers do not need to “help” the comfort layers with pressure relief, their ability to conform to your body profile is far less important and your choices in support layers are larger as almost any firm support layer is suitable for this construction.
A soft comfort layer over a firm or even extra firm support layer would be an example of this.
In a progressive construction, the upper comfort layers are generally thinner and/or very soft and need to "borrow" from the support layers beneath to form a cradle and relieve pressure. These mattresses usually have several layers that become "progressively" firmer as you sink in deeper, and the difference between adjacent layers is smaller than with a differential construction. The layer below the comfort layer plays a dual role by helping the comfort layer with pressure relief/lumbar support and helping the bottom layer with spinal alignment. This can be done with either a middle transition layer or with the use of a support layer material which is softer and more conforming on the top and becomes firmer more quickly with deeper compression.
This method can be more difficult to get right but the results can be more accurate and individualized than a differential construction. Because the support layers are helping with pressure relief and lumbar support, any pressure relieving comfort material can be used including those that are less resilient such as memory foam or natural fibers. The choice of support layers however becomes more restricted since they require more specialized abilities beyond simple "firmness" such as the ability to be softer and conforming on top (with initial compression) and firmer underneath (with deeper compression).
A softer/thinner comfort layer over a medium middle layer and a firm bottom layer would be an example of this construction.
The body has 3 main areas where weight and the thickness of the profile can be very different. These are the pelvic or hip area which is often wider, especially in women, and almost always the heaviest area of the body; the lumbar area which is much thinner, lighter, and more recessed in most people; and the shoulder upper chest area which is lighter than the hips but often wider and larger, especially in men. The widely different needs of these three areas in more difficult circumstances such as unusual weight or body profiles are sometimes outside of the range of even the best materials using either differential or progressive constructions. In these cases zoning can be the answer to a perfect mattress.
Zoning uses different zones of material or firmness in different areas of a comfort or support layer such as a firmer zone under the hips to keep them from sinking down too far. It can also be quite complex and in many cases poorly understood by those who sell mattresses. Incorrect zoning schemes can do much more harm than good so it is usually a good idea to only use it when circumstances warrant. Different zoning schemes may use any type of comfort layers over any type of support layer depending on the type of zoning that is being used and the individual circumstances or difficulties that need to be addressed.
The most effective zoning schemes usually have either 2 or 3 zones in different "arrangements. More than this is of questionable benefit and often used to justify a more expensive mattress that may not even be an appropriate choice.
There are several other layers that are part of either some or all mattresses and are used to complete your mattress.These are ...
Quilting layer: Commonly used as a layer above the comfort layer. Usually made from foam or fibers and forms a separate but interconnected part of the comfort layer. It can affect breathability, temperature regulation, and pressure relief as well as overall feel and can also be used for fine tuning.
Ticking: This is the fabric that surrounds the mattress and it too can affect breathability, temperature regulation, and pressure relief as well as have a significant effect on the overall feel of the mattress.
Fire Barrier: This is used to prevent a mattress from bursting into flame and preventing "flashover" from either a smoldering heat source or with an open flame. The "open flame" regulation that all mattresses now need to comply with was added in 2007 to the first "smoldering heat source" regulation that was already in effect.
Insulator: This is a layer which is used over an innerspring to prevent the layers above it from shifting into the innerspring and is also used to alter the feel or response of the innerspring itself.
Each of these different methods of construction and additional layers are discussed in more detail in the pages of this section.