6 pounds per cubic foot the intermediate layer is approximately 1 12 inches thick approximately 5 9 times the thickness of each of the upper and lower layers with a weight basis of about 5 0 ounces per square foot and a density of about 3 3 pounds per cubic foot approximately 55 percent of the density of each of the upper and lower layers the resulting multi layer insulating mat then has a combined thickness of about 1 5 inches an average weight basis of about 8 ounces per square foot and an average density of about 4 pounds per cubic foot for an insulating mat with a final thickness of about two inches the first layer begins with a loose batt that is about 3 inches thick the loose batt is subjected to needle punching with a puncture density of between about 500 ppsi and 600 ppsi to produce a mat having a thickness of about 0 24 inches a weight basis of about 1 9 ounces per square foot and a density of about 6 0 pounds per cubic foot in this embodiment the first and second or lower and upper layers are formed in the same manner so that they have the.