Thermophysical Characterization of Bioresource Construction Materials for Sustainable Tribal Housing in Hill Regions

Abstract

This study presents an integrated assessment of traditional bioresource construction materials used by indigenous communities in the Nilgiris district, Tamil Nadu, focusing on their thermophysical properties, environmental benefits, and cultural relevance within the region’s unique subtropical highland climate. Samples were collected from tribal settlements of the Toda, Kattunayakans, Kurumba, Kota, and Irula communities, spanning altitudes from 900 m to 2636 m, where temperatures range between 0 °C and 25 °C. Key materials studied include bamboo, wood species (teak, eucalyptus, silver oak, white Naga tree), grass, calcareous binder, and bark skin. Thermal characterization using differential scanning calorimetry revealed specific heat (Cp) capacities ranging from 2.224 kJ∙(kg⁻¹∙K⁻¹) (Toda bamboo) to 2.435 kJ∙(kg⁻¹∙K⁻¹) (Kurumba bamboo), with roofing grass thatch exhibiting a notably high Cp of 4.543 kJ∙(kg⁻¹∙K⁻¹) and calcareous binder reaching 4.703 kJ∙(kg⁻¹∙K⁻¹). Thermal conductivity values for bamboo were found between 0.17 W∙(m⁻¹∙K⁻¹) and 0.23 W∙(m⁻¹∙K⁻¹), yielding thermal resistance (R-values) of approximately 2.86 (m²∙K)∙W⁻¹ to 5.00 (m²∙K)∙W⁻¹ per meter thickness, significantly outperforming conventional concrete (R ≈ 0.71 (m²∙K)∙W⁻¹). Straw and reed materials demonstrated exceptionally high R-values up to 15.38 (m²∙K)∙W⁻¹ and 30.13 (m²∙K)∙W⁻¹, respectively, confirming their superior insulation capabilities. Environmental analysis highlighted bamboo’s rapid growth rate (30 cm∙day⁻¹ to 100 cm∙day⁻¹), low embodied energy (30 % to 40 % less than concrete), and carbon sequestration potential (up to 17 tons CO₂/ha/year). These bio-based materials offer thermal comfort enhancements of 4 °C to 6 °C above ambient in cold conditions and contribute to reducing construction-related carbon emissions by nearly 50 %.