This work presents an experimental study to investigate the heat conduction coefficient of the density-layered stone wool plates insulation materials used in heat insulation applications. The stone wools, which have 70, 100, and 150 kg/m3 of densities, have been combined in different thicknesses to 60 mm. The aim of this layer combination is to benefit from lower heat conductivity and lightness of the lower density stone wools and the better strength of higher density stone wools. First, the single-layer stone wools with 60 mm of thickness, which is in the insulation market, have been tested. Then, they have been combined in different thicknesses, with a total thickness of 60 mm. A total of 18 samples have been produced, and the thermal conductivity of samples has been measured experimentally. Consequently, the heat conduction coefficient of density-layered stone wools and their weights have been compared experimentally. At the end of the present study, it is observed that density-layered stone wool plates play a critical role in improving the heat conductivity and lowering the weight of high-density plates. When combining 10 mm thick 150 kg/m3 density stone wool with 50 mm thick 70 kg/m3 density stone wool, the heat conductivity has been improved by 3.52% and the weight of the 1 m2 plate has reduced by 4 kg (44%) according to the stone wool with 150 kg/m3 of density.