The choice of construction and thermal insulation materials relies primarily on their thermophysical properties, notably thermal conductivity (λ), specific heat capacity (cp), and thermal diffusivity (a). Accurate determination of these properties is essential for evaluating the thermal behavior of materials in buildings. Various experimental methods, classified according to the type of heat transfer regime (steady-state or transient), are used for this purpose. This study fits into this context by focusing on the mathematical modeling of the Flash method, in accordance with ASTM standard E1461-13. This method, which was designed and developed in our laboratory, allows for the determination of the thermal diffusivity a (m2/s) of materials under transient conditions. The developed mathematical model is based on the assumption of one-dimensional heat transfer, taking into account heat losses on both the front and rear faces of the sample being characterized. The shape of the thermal pulse generated by the apparatus was experimentally determined, and the recorded data were modeled using a script written in the Mathematica language. The characterization results will be presented and discussed.