This study evaluates the efficiency of phase change materials (PCMs) in improvements in thermal performance and thermal comfort of a residential building. The heat transfer of concrete containing PCM, which has been experimentally examined, was numerically modeled and validated in this study. PCMs with melting temperatures ranging from 19 to 29 degrees C and thicknesses of 5 and 10 mm were applied in different building elements. After finding the optimum PCM with respect to the energy analysis, the impacts of the meteorological parameters and cooling and heating loads were evaluated. The experimental results were in a good agreement with the EnergyPlus PCM module in the numerical model. The results indicated that models integrated with PCM are able to improve the indoor comfort and to reduce the heating and cooling loads and temperature fluctuations. The PCM with a melting temperature of 21 degrees C and thickness of 10 mm positioned in the roof and wall showed the best performance in the energy consumption and transfering the loads away from the peak demand times. The environmental analysis indicated that the total CO2 emission reduction would be about 264 tone when PCM with 10 mm thick is applied to a building with a life span of 50 years. The shortest payback period for building using PCMconcrete was 16.6 years. (c) 2020 Elsevier Ltd. All rights reserved.