Implementation of a double layer of PCM integrated into the building exterior walls for reducing annual energy consumption: Effect of PCM wallboards position

The implementation of phase change materials (PCMs) in the building envelope for thermal management has grabbed the attention of many researchers. The PCM wallboards can be embedded in different positions in the exterior walls of the building, and a distinct thermal performance of the building has been achieved. This paper aims to simulate the heating/cooling performance of a four-story residential building located in Tehran (the capital of Iran), considering a double-layer of PCM wallboards next to the thermal insulation layer. This research examines the different positions of PCM wallboards within the building walls to establish their optimal location. In addition, the advantage of using a double-layer of PCM wallboards with different melting points compared to a single-layer one is studied. The results showed that the arrangement of PCM wallboards along with a thermal insulation layer can influence the energy consumption of the building. The results revealed that height can affect the placement of PCM wallboard and insulation layers. It was found that RT18/Insulation/RT28 is the best arrangement for the 1st, 2nd, and 3rd floors, while RT28/RT18/Insulation is the best mode to be embedded in the exterior wall of the 4th floor in terms of the lowest heating energy consumption in the building. Considering the cooling energy consumption, RT18/RT28/Insulation is the best arrangement for the 1st floor; RT18/Insulation/RT28 is the best arrangement for the 2nd and 3rd floors; and RT28/RT18/Insulation is the best arrangement for the 4th floor. In general, using the best conditions for each floor saves about 6.6 % and 2.8 % of heating and cooling energy, respectively.