Climate change and environmental degradation pose critical challenges in tropical rural regions, where housing infrastructure remains highly vulnerable to thermal stress and hydrometeorological extremes. This study presents the development and empirical assessment of a modular extensive green roof system designed specifically for humid tropical climates. Employing locally sourced materials such as coconut coir, pumice stone, and endemic plant species, the system fosters ecological integration and cost-effective scalability. Two prototype configurations, varying in substrate depth, were field-tested over nine months. Key performance indicators including rainfall retention (42.5%), infiltration delay (mean 192 s), indoor temperature reduction (2.43 °C), and relative humidity increase (13%) demonstrated significant environmental benefits. Estimated carbon sequestration reached 4.82 kg CO₂/m²/year based on aboveground biomass accumulation. Statistical analyses using Student’s t-test, one-way ANOVA, and Tukey HSD confirmed substrate depth as a critical determinant of thermal and hydrological performance (p < 0.001). These findings underscore the feasibility of low-cost, nature-based solutions for climate-resilient housing, supporting SDGs 6, 9, and 11 in vulnerable communities of the Global South.