Applicability of phase change materials for building envelopes in the U.S. according to ASHRAE standard

In the United States, buildings consume 25% of the energy budget. In this study, the reduction of energy demand in hot-arid climates in the U.S. was investigated numerically regarding the addition of phase change materials (PCMs). To conduct a comprehensive study, 5600 cases with 6 parameters, including climate/weather, internal temperature, installation location, PCM type, internal temperature changes, and PCM thickness were examined. The results were discussed in the context of two scenarios. In the first scenario, the building was without an air conditioning system and therefore the internal temperature varied without limits. In the second scenario, energy consumption and the inside temperature was regulated. In both scenarios, the main goal was finding the best PCM type and location. The results showed that for both scenarios, the best layer for PCM installation is the third or the fifth layer. In the first scenario, PCM23 is recommended first and followed by PCM22 and PCM24. In the second scenario, the best PCM was dependent on its thickness. At 5 cm, PCM23 is the first candidate, followed by PCM24 and PCM22, while at 10 cm, PCM22, PCM24, and PCM23 are suggested. Adding PCM in some zones had very surprising effects. In the second scenario, by installing the apparent PCM in the best layer, annual building energy demand can be reduced to zero. In addition, it was found that the energy-saving due to PCM installation is not more than 20.8 kWh/m2.