Enhancing building roof insulation: A comparative examination of PCM layers integrated with and without nanoparticles

• Investigate numerically the thermal performance of an Iraqi roof under real boundary conditions using a 3D model using the enthalpy method by FORTRAN. • Utilizing a pure PCM layer and a nano-enhanced PCM layer into the roof to investigate the thermal performance of the roof. • Significant reduction in the peak temperature of the inner test roof by about 2.4℃ for pure PCM and 1.1℃ for NEPCM compared to the domestic roof. • Utilization of pure PCM gives better insulation than nano-enhanced PCM. • Using pure PCM extends the time delay of peak load by 2 h, while NEPCM reduces it to 0.5 h. This paper evaluates the thermal insulation potential of a roof embedded with phase-change materials (PCM) and nano-enhanced PCM (NEPCM) in Iraq’s hot climate. The primary goal is to investigate the effectiveness of these materials in reducing indoor heat transfer, thereby enhancing energy efficiency, using a numerical model based on finite volume and enthalpy methods in a three-dimensional spatial domain. The study compares the performance of roofs equipped with pure PCM and NEPCM layers. Results indicate that the PCM layer significantly lowers peak indoor surface temperatures and delays peak heat transfer, achieving a 2.4 °C temperature reduction with pure PCM and a 1.1 °C reduction with NEPCM. Furthermore, using pure PCM extends the time delay of peak load by 2 h, while NEPCM reduces it to 0.5 h, and the increasing nanoparticle ratio in PCM leads to an increase in the inner surface temperature of the roof. Findings also suggest optimizing the PCM layer’s thickness and adjusting its melting temperature to around 37 °C enhance its thermal insulation capabilities.