In recent years, research on low-energy building materials has actively progressed, with a growing interest in eco-friendly building. Strong interest has also been shown in the wooden flooring sector to improve the thermal conductivity of under floor heating systems. This study focused on improving the thermal transfer performance of radiant floor heating systems by enhancing the characteristics of the existing polyethylene underlay foam (PE foam). The thermal conductivity of the modified PE underlay foam (MPE foam) was increased by 48.1% compared with that of the PE foam. The theoretical heat flux was also calculated for the thermal conductivity, the results of which showed that the heat flux of the MPE foam was enhanced by 24.1%, compared with that of the underlay foam. To confirm the theoretical results, flooring systems were installed in the laboratory as a replica for the experiment. The velocity of thermal transfer for the laminated flooring used with the MPE foam was slower than the engineered flooring in which adhesive was used. However, the velocity of transfer was faster for the laminate flooring incorporating the PE foam. In addition, after the heating was switched off, the heat storage capacity of the laminate flooring with the modified PE foam was the highest among the tested samples.