The increasing demand for sustainable and fire-safe construction materials has encouraged the development of bio-based composites for building applications such as ceiling boards. However, their inherent flammability and moisture sensitivity remain key challenges. This study investigates the performance of eco-friendly fire-retardant composite ceiling boards fabricated from corn starch, sodium silicate, eggshell powder, and recycled fiber using a Taguchi mixture design. Eight formulations were prepared via the hand lay-up method and evaluated for thermal, fire, mechanical, and hygroscopic properties. The results show that material composition significantly influences performance. The lowest thermal conductivity (0.4733 W/mK) was obtained for Sample S5, indicating superior insulation, while Sample S3 exhibited the highest degradation temperature (558°C), reflecting excellent thermal stability. The maximum tensile strength (3.01 MPa) was achieved by Sample S1. Notably, Sample S8 demonstrated the best fire-retardant performance, with the lowest flammability weight loss (21%), along with good resistance to direct heat and the lowest swelling (22%), indicating improved dimensional stability. Although the developed composites exhibit promising fire-retardant behavior and sustainability advantages, further improvements in thermal insulation and moisture resistance are required to meet commercial standards. These findings highlight the potential of bio-based composites as viable alternatives for ceiling board applications.

bio-based composites, fire-retardant material, ceiling board application, thermal stability, sustainable construction