Enhancing thermal, acoustic, and mechanical performance of cob and wattle-and-daub walls: A parametric study on the combined role of straw and reed

Cob and wattle-and-daub techniques, characteristic of vernacular architecture, offer a compelling path towards low-carbon construction. However, missing the experimental data on the thermal, acoustic, and mechanical performance of wattle-and-daub, and limited acoustic performance data for cob, hinders widespread adoption and their relevance in contemporary building frameworks. This study addresses this shortfall by investigating the effects of straw fibers and reed reinforcement on cob and wattle-in-daub systemsS. Two formulations were tested: heavy (H) with 2 wt% of straw for load-bearing walls, and Lightweight (LW) with 10 wt% straw for non-structural elements, each assessed with and without reed reinforcement. Results revealed significant performance enhancements, including a 51 % reduction in thermal conductivity for reinforced LW mixtures (0.197 Wm^−1.K⁻¹), and a 43 % decrease for H formulation (0.227 Wm^−1.K⁻¹). Compressive strengths increased by 140 % (2.74 MPa) and 150 % (2.85 MPa) for reinforced LW and H configurations using reed, respectively, while flexural strengths improved by up to 89 % (0.68 MPa) and 69 % (0.61 MPa), respectively. Acoustically, the reinforced H configuration demonstrated the best transmission performance in the mid and high frequencies (250 Hz–1000 Hz), reaching 23 dB in 630 Hz. While the best noise absorption was observed by the reinforced LW configuration at mid to high frequencies (250 Hz–500 Hz), reaching 94 dB at 500 Hz. These results highlight the potential of combining straw fibers and reed reinforcement to enhance traditional construction methods, offering improved performance while maintaining sustainability and cultural significance.