This paper investigates the dynamics of thermal effect on thermal conductivity, k-value, at different operating temperatures and moisture levels of polystyrene expanded insulation material (EPS) by using computational modeling of heat transport. In building energy analysis, the heat transfer, through its envelope, usually considers a constant single k-value and neglects the effect of the moisture content within the insulation when performing a building energy analysis assessment. In reality, the building envelope is subjected to the combined thermal and moisture gradients. Therefore, an accurate analysis requires a simultaneous calculation of both sensible and latent effects. The purpose of this paper is to analyze the dynamics thermal effect on k-value of EPS by using the conduction finite difference (CondFD). The results of this research show a slight difference in the thermal conductivity value of EPS insulation at different operating temperatures for different densities of the material. However, a greater difference has been observed at higher moisture contents compared with the dry sample when the thermal conductivity of the insulation was a function of temperature.