The integration of fiber additives into adobe offers an economical, ecological, and energy-efficient solution to reduce the energy consumption and greenhouse gas emissions associated with the construction and building sectors. This study investigates the incorporation of locally available Juncus acutus (JA) fibers into a red clay matrix to enhance the thermophysical properties of the composite. Fiber contents of 2%, 4%, and 6% by weight of the binder were used in the preparation of the specimens. The thermophysical characteristics of the composites were evaluated using the hot disk method, a non-destructive technique. Experimental results reveal that the addition of JA fibers significantly reduces the thermal conductivity of the composite, achieving a reduction of over 50%. Furthermore, to assess the practical application of this bio-composite in buildings, a Computational Fluid Dynamics (CFD) analysis was performed using ANSYS software. The simulation results demonstrate the potential of these bio-composites to substantially improve energy efficiency in buildings. These findings support the use of locally sourced, sustainable, and energy-efficient materials as promising alternatives to conventional adobe.