The maximum mass percentage of n-octadecane retained by GP was found to be 8. FT-IR results showed that the interaction between the components of composite PCM is physical in nature. The melting and freezing temperatures of the composite PCM were found to be 26.93 ¡ãC and 25.03 ¡ãC while the latent heat of melting and freezing were 18.97 J/g and 18.95 J/g. TGA and thermal cycling results confirmed that the composite PCM is thermally stable and reliable. Thermal performance test showed that the cement paste panel with composite PCM reduced the indoor temperature by 3 ¡ãC. It can be concluded that the composite PCM can be used for thermal energy storage applications in buildings. Its usage will provide sustainable solution to reuse the waste glass. Thus, landfills can be saved for useful applications.