There seems to be an abundance of foam densities and layer thicknesses of Memory Foam – what does it all mean?
Virtually all Memory Foam mattresses consist of two foam layers laminated together. The top Memory Foam layer serves the purpose of comfort and pressure point relief, whereas the bottom layer is made from high density polyurethane foam to provide orthopedic support. More advanced designs, such as Somnolence and Tempur-Pedic in addition have a middle convoluted air-flow layer for increased comfort. Thickness of Memory Foam layer The ideal and most common thickness of the Memory Foam layer is three inches regardless of the overall thickness of the mattress. A two-inch Memory Foam layer is considered too thin for optimum pressure point relief (also see “topper” section above) while a Memory Foam layer of four inches or more (especially a low density foam of 4.0 lbs or less) can result in the average-weight person penetrating too deeply into the foam (the ditch effect), which can result in difficulty changing sleep positions. All Somnolence mattresses have a Memory Foam layer of three inch
