Thermal barrier performance of natural fiber-reinforced biocomposite panels with the reflective surface for conserving heat energy in buildings

• The thermal performance of heat-insulating colored and white composites was investigated • Color displayed a minimal impact on the conductive heat resistance of composite materials. • Reflective white surface can substantially resist the transfer of radiant heat through the composite. • The energy emitted by light sources was adequately reflected by the white composite and absorbed by the black ones. • White composite has superior resistance to conductive and radiant heat and the potential to save energy in buildings. This study investigates the thermal barrier properties of fiber-reinforced composites with heat reflective surfaces for building applications. Biocomposites made of natural cotton fiber with white and four distinct colors, such as red, yellow, blue, and black, were developed employing a compression molding technique. Among the studied composites, the white cotton composite owing to reflective surface has the lowest thermal conductivity of 0.0687 W/m·K, which was the maximum for its black counterpart with the value of 0.0823 W/m·K. The white composite, in contrast, exhibited higher conductive heat resistance (0.0582 m 2 ·K/W) than the black ones (0.04862 m 2 ·K/W). The evaluation of the radiative heat resistance using an incandescent lamp and sunlight showed the superior resistance of white composite to radiant heat transfer due to its high reflectance of electromagnetic radiation, making it an effective reflector and heat insulator material for thermal energy conservation. Additionally, the thermogravimetric analysis revealed adequate thermal stability with a similar trend in the degradation pattern of composites at elevated temperatures, confirming a negligible impact of color on thermal stability. The overall outcomes of this study suggest fiber-reinforced composites with reflective (white) surfaces can considerably resist the transfer of conductive and radiative heat than colored cotton materials and, therefore, can be employed as better heat-insulating panels in buildings for lowering thermal loads to maintain favorable indoor temperature.