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The amount of energy expenditure in buildings is 30–40% of the total energy consumption in the world and this share will increase to 50% by 2050. Therefore, reducing energy consumption is a necessity and one of the ways to reduce energy expenditure in buildings is to use passive methods. The use of DSF is expanding as a new approach for building facades due to its ability to prevent excessive heat by absorbing solar radiation. For this purpose, the energy performance of PCM and DSF was studied in three climates of Tehran, Tabriz, and Kish Island, to reveal their energy saving potential. Based on the results of this article, the use of PCM in different layers of DFS can result in a considerable energy saving in Iran residential sector. PCM is integrated both in the external wall and in the partition wall of the DoubleSkin Façade under three different climates. DesignBuilder is used for the thermal analysis of the building. The effects of melting temperature, location of PCM layer in the wall have been investigated. The results showed that we will witness the highest total energy savings percentage in the cold semi-arid climate because of using Infinite RPCM23 in October, amounting to 91.6%. In addition, by using Infinite RPCM25 in warm semi-arid climates in the highest percentage of heating load savings is 99.9% in December and January, and the highest percentage of cooling load savings in cold semi-arid climates is 67.5% by using InfiniteRPCM23 in September. [ABSTRACT FROM AUTHOR]

The utilization of phase change materials (PCMs) in buildings leads to the reduction of energy consumption and maintaining the indoor temperature within the comfort range. The PCM performance strongly depends on the climatic conditions, causing a major challenge. To overcome this issue, the employment of a double-layer PCM system is introduced. The energy and economic assessments of various double PCM systems in the building located in different climatic conditions of Iran have been conducted for the first time. In this study, two PCM wallboards with different enthalpy and melting temperatures were embedded in the external walls of a residential building located in various climatic regions of Iran. The performance of the double-layer PCM system in five cities of Iran including Tehran, Isfahan, Shiraz, Tabriz, and Bandar Abbas during hot and cold months of the year was evaluated from energy and economic viewpoints. It was inferred that embedding a double-layer PCM system reduces the heating/cooling energy consumption compared to single-layer ones. It was concluded that the RT18/RT28 double PCM system was the best candidate to be employed in the external walls of the building located in Tehran and Shiraz, which reduced the total energy consumption of the building up to 6.26% and 5.17%. The RT18/RT22 double PCM system was the most efficient system for the building placed in Tabriz and Isfahan reducing the total energy consumption up to 4.41% and 3.87%, and the RT22/RT28 double PCM system had the best performance in the building located in Bandar Abbas, which could save 6.58% of total energy. Moreover, it was concluded that the use of a double PCM system reduced temperature fluctuations in the external walls. In addition, the economic analysis was performed using the dynamic payback period and the results revealed that the employment of a double-layer PCM system reduced the investment return period by up to 50%. [ABSTRACT FROM AUTHOR]