A phase change material (PCM) composite was prepared by impregnating propyl palmitate in expanded perlite (EP, as a support matrix), and its thermal buffering performance was tested in building applications. Five composites with varying PCM contents, i.e., 60, 55, 50, 45, and 40%, were prepared, and the composite with 55 wt % (EP-55) was chosen for thermal buffering performance analysis. All composite samples showed melting between 18.5 and 18.8 degrees C (as a PCM), while attenuated total reflection-infrared spectroscopy analysis confirmed simple physical adsorption occurring between the PCM and EP. Differential scanning calorimetry measurements (EP-55) showed a phase change enthalpy of 81.98 +/- 1 J g(-1), and stable performance during 1000 thermal cycles with the EP-55 composite confirmed appreciable thermal stability and reliability. The thermal buffering performance of the composite was tested in a building model, which was simulated using COMSOL Multiphysics 5.5. The unsteady-state energy (conduction/convection/radiation and latent heat of a PCM) transport from a source to the building was expressed mathematically along with its boundary conditions. The model was validated using a blank and with a composite, which was later applied to predict another unknown case. The model-predicted temperatures could very closely match (< +/- 4.0%) with experimental values.