A major part of energy consumption is reported from the residential and commercial buildings due to the large usage of mechanical devices to maintain a comfortable indoor ambiance. Thermal conductivity of the materials used in these buildings can be reduced by using low density materials and an efficient thermal energy storage strategy. In the present paper, the thermal performance of a building envelope was improved by incorporating phase change material (PCM) into the foam concrete mix. At first, PCM was developed by using a light weight material, expanded vermiculite (EV) impregnated with capric acid (CA) and ethyl alcohol (EA) under vacuum conditions. Different foam composite mixes were prepared and experimentally tested. Foam concrete mixtures with EV, CA-EA/EV based PCM, and PCM with added nano silica and coir fiber combinations (PSC) were pre-pared by the replacement of fine aggregate (M-sand) in various weight percentages. This study reveals that PCM with a CA to EV proportion of 55% (wt.) had the maximum adsorption and stability, as assessed through liquid leakage. In addition to improving thermal efficiency, PCM enhanced foam concrete composites showed improved mechanical, hydration, durability, and thermal characteristics. In comparison to the control foam concrete and PCM foam concrete mixes, the addition of nano silica and coir fiber added foam concrete mixtures (PSC) demonstrated improved strength and shrinkage qualities. These improved properties are attributed to the pozzolanic activity of nano silica and the bridging effects resulting from the fiber to micro cracks. Apart from the durability and strength characteristics, scanning electron microscopy (SEM), energy-dispersive X-ray spectros-copy (EDS), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA) were adopted to characterize the morphological, chemical, and thermal aspects of the different foamed concrete mixtures. The DSC results proved that the PSC-5% foam concrete mixture had latent heat capacities of 43.90 J/g for cooling and 69.16 J/g for heating, with melting and solidification temperatures of 31.51 degrees C and of 21.77 degrees C, respectively. TGA also revealed that the proposed PCM composite has a high thermal resistance. The PSC-5% shows better -compatibility as per SEM and EDS tests by the proper penetration of the nano silica in the foamed composi-tes through the pores. Finally, the thermal analysis tests demonstrated that the PSC-5% has a thermal conductivity of 0.129 W/m-K, which is 49.60% lesser than the foam concrete control sample, and also possesses an improved heat storage capacity, which ensures better thermal comfort in buildings.
