<p>The experimental study is done to discern the thermal properties of lime block by impregnating the natural Phase Change Material (PCM) to sustain the change in weather conditions inside the structure without being affected by the environmental changes. PCM is impregnated in the lime block at different percentages of 2.5%, 5%, and 7.5% to the weight of the lime, which reacts to the environmental changes and acts as a shield to the structure by closing the pores developed in the hydraulic lime mortar-based block. To study the comparative difference between the lime block with and without PCM, thermal conductivity and thermal resistivity tests are conducted using which the thermal diffusivity and thermal effusivity are determined. Microstructure analysis is also performed for the PCM-based lime block to analyze the chemical components of the mix. This study discovers the storage of energy in the structures, and it is achieved by reduction in the thermal conductivity with the addition of PCM at different percentages. The strength of the lime block is gradually reduced as the percentage of PCM is increased. The PCM block with 5% bee wax recorded the lowest thermal conductivity with 16% less compared to the reference block, but the compressive strength reduced marginally by 2%. The energy storage capacity of the designed PCM block is about 463.7&#xa0;J, which is nearly 23% more than the reference blocks. Hence the developed PCM block could be a potential thermal energy storage solution in building applications.</p> Graphical abstract <p></p>