In this study, thermal energy storage properties and thermal reliability some fatty acid esters/building material composites as novel form-stable phase change materials (PCMs) were investigated. The form-stable composite PCMs were prepared by absorbing galactitol hexa myristate (GHM) and galactitol hexa laurate (GHL) esters into porous networks of diatomite, perlite and vermiculite. In composite PCMs, fatty acid esters were used as energy storage materials while diatomite, perlite and vermiculite were used as building materials. The prepared composite PCMs were characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. The SEM results proved that the esters were well confined into the building materials. The maximum mass percentages of GHM adsorbed by perlite, diatomite and vermiculite were determined as 67, 55 and 52 wt%, respectively as they were found for GHL to be 70, 51 and 39 wt%, respectively. Thermal properties and thermal stabilities of the form-stable composite PCMs were determined using differential scanning calorimetry (DSC) analysis. The DSC results showed that the melting temperatures and latent heat values of the PCMs are in range of about 39-46 degrees C and 61-121 J/g. The thermal cycling test revealed that the composite PCMs have good thermal reliability and chemical stability. TG analysis revealed that the composite PCMs had high thermal durability property above their working temperature ranges. Moreover, the thermal conductivities of the PCMs were increased by adding the expanded graphite (EG) in mass fraction of 5%. Based on all results, it was also concluded that the prepared six composite PCMs had important potential for thermal energy storage applications such as solar space heating and cooling applications in buildings. (C) 2012 Elsevier B.V. All rights reserved.