Potential Use of Castor Oil-Based Polyurethane Matrix Composite with Miriti Fiber Filling as Thermal Insulation Applied to Metal Tiles

The Amazon biome's climate, with annual temperatures above 30 °C and humidity over 90%, poses challenges for building thermally comfortable structures without expensive cooling systems. This study developed a castor oil-based polyurethane (PU) composite with miriti fiber (<i>Mauritia flexuosa</i>) as a roof thermal blanket, comparing its performance to fiber cement, ceramic, and metal tiles. Measurements were conducted over 136 days at the Federal Institute of Education, Science and Technology of Pará, Campus Belém. From August to October 2022, the fiber cement tile (CT) showed average thermal reductions of 5.9475 °C, 6.13388 °C, and 6.37368 °C, while the FCT coating had more modest reductions of 3.6634 °C, 3.63291 °C, and 3.60598 °C. In November and December 2023, the PU/miriti coating reached the highest reductions, 18.64058 °C and 17.88021 °C. Meanwhile, FCT recorded lower values of 1.74124 °C and 1.74721 °C. Observations show fiber cement allowed the highest heat transfer, whereas a metal tile combined with the PU/miriti composite provided better thermal performance than fiber cement and ceramic, meeting standards approval. The findings highlight the PU/miriti composite's viability for roofing in hot, humid climates where maintaining lower indoor temperatures is essential. By reducing reliance on mechanical cooling, this technology can foster sustainable, cost-effective building practices in the region.