The current research investigates the influence of fiber volume fraction on effective thermal conductivity (keff) in polymeric materials. This study identifies a method to improve the insulating property of a traditional fiber-reinforced polymer composite. A quantitative relationship for the heat transfer coefficients of polymer composites reinforced with fiber is created utilizing the law of minimal thermal performance and the equal law of particular similar thermal conductivity. To validate this statistical equation, two sets of polymer composites with fiber concentrations ranging from 0 to 15.7 vol percent were hand-built. Natural fibers such as banana fibers are integrated into an epoxy matrix in one set of composites, whilst glass fiber is employed as a filler material in another set, although the matrix material remains unchanged. Thermal conductivities of these composite materials are tested in accordance with ASTM standard E-1530 using the Unit herm TM Model 2022 tester, which operates on the double shielded heat flow concept. Furthermore, using the commercially accessible finite element tool ANSYS, the finite element technique (FEM) is employed to quantitatively measure the k eff of such composites. The numerical values generated by the proposed statistical model are then compared to empirically measured values. The analytical and simulation results reveal that the appropriate heat conductivity value for both sets of composites steadily declines as fiber concentration increases. Because none of the models developed properly anticipated the rate of heat transfer of the composites, the results generated from the proposed system closely match the experimental data. This study shows that as the fiber loading in the composite increases, so does the heat transmission rate. The use of 15.7 vol percent glass fiber in epoxy resin reduces heat conductivity by around 8%, whereas a 12 percent decrease is observed when the banana fiber is used as a filler. This research backs up the conceptual approach while indicating that finite element analysis is an effective tool for such investigations. This thermal insulating, fiber-reinforced polymer composites have potential applications in insulating boards, food containers, thermo flasks, construction materials, and so on due to their low thermal conductivity and lightweight.