An Introduction to Differential Construction

Pressure relief and differential construction.

The common factor in all differential constructions is that they use a comfort layer that is THICKER than the recessed areas or "gaps" in a sleeping profile. If for example you need a pressure relieving cradle that is 3" deep (average side sleeper), then a differential construction could have a comfort layer that was at least 3" thick and usually a little more. In this type of construction, the comfort layer is designed to do all the work of forming a pressure relieving cradle and supporting the recessed lumbar area and the support layers below it are only used to keep the spine in alignment by preventing any further sinking down by the heavier parts of the body. This means that in this construction, a comfort layer needs to have all the qualities that are necessary by itself as it does not “borrow” qualities from the layer below it. This means that for pressure relief, it needs enough softness and point elasticity, and for lumbar support it needs a higher sag factor and resiliency. In other words, if you needed a 3” cradle for good pressure relief then you would use a comfort layer that was about 3” - 3.5” thick. If you needed a 2” cradle for pressure relief, then you would likely choose a comfort layer that was 2” – 2.5” thick. The comfort layer would always be at least as thick as the cradle that you need and usually a little thicker.

The advantages and disadvantages to mattresses with differential construction:


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