Energy consumption has been increasing rapidly in this present world Simultaneously, the effect on the earth’s atmosphere is also increasing at a very high rate. The incorporation of phase change material (PCM) in bricks is motivated to increase the energy efficiency in households. The scientific community has focused on organic phase change materials (PCM) as a potential building technology for passive thermal management (Ürge-Vorsatz et al. in Renew Sustain Energy Rev 41:85–98, 2015 [1]). Because they are easily accessible, non-toxic, non-corrosive, and have a phase transition range that is within the thermal comfort range due to their chemical stability. A study has been done to improve low thermal conductivity and leakage problem of OM35 PCM by mixing it with sugarcane bagasse biochar to create a bio-composite PCM (Bordoloi et al., J. Energy Storage 55:105801, 2022 [2]). This research concentrated on finding the impact of heat transfer in a bio-composite PCM (SCB-OM35) infused calcium silicate brick with a 20 mm thickness, compared to an uninfused one, was evaluated using numerical simulations in ANSYS software. The numerical study has been carried out in a brick wall of dimension 4 m × 3 m × 0.05 m. The numerical study shows a temperature drop of 1.727 °C throughout the dimension of bio-composite PCM incorporated brick as compared to the normal brick. The computational results reveal that the selected PCM significantly reduces heat transfer from the exterior wall to the interior wall. This thermal regulation not only decreases overall energy consumption but also contributes to the greater comforts for occupants.