This study aims to enhance the insulation property of polypropylene (PP) by developing it into a multi-hollow structured board using 3D printing technology. A previous experimental study determined the effective thermal conductivity of the porous PP board was experimentally determined using a hot box test, yielding a value of 0.0033 W/mK, which represents a significant improvement over conventional building insulator. To validate the experimental results, a numerical simulation using COMSOL Multiphysics software was conducted to model the heat transfer process within the porous PP board. The simulation employed an appropriate methodology, including parameter definition, geometry creation, material definition, steady-state porous heat transfer module, initial and boundary conditions, meshing, and study. The numerical analysis focused on determining the indoor surface temperature, evaluating the total heat flux, and calculating the effective thermal conductivity of the porous PP board. The simulation results revealed an effective thermal conductivity of 0.0036 W/mK, which closely matches the experimentally obtained value from the hot box test. The agreement between the experimental and numerical results validates the effectiveness of the multi-hollow structured PP board as a superior insulating material. This study demonstrates the potential of combining 3D printing technology with materials like polypropylene to develop highly efficient insulation solutions for building applications.