Design and evaluate urban green roofs for thermal regulation and biodiversity enhancement

Thesis Abstract

Urban areas are increasingly challenged by the dual issues of rising temperatures due to the urban heat island effect and declining biodiversity amidst rapid urbanization. The integration of green infrastructure, particularly green roofs, has emerged as a vital strategy to mitigate these environmental challenges, yet empirical data on their optimal design, thermal performance, and contribution to biodiversity enhancement remains limited. This study aims to design and evaluate the effectiveness of various green roof configurations in terms of thermal regulation and biodiversity support within an urban setting. Specifically, it investigates the influence of substrate depth, plant species selection, and irrigation regimes on temperature reduction and species richness, thereby providing practical guidelines for sustainable urban roof greening. The research adopts a mixed-methods approach, combining quantitative experimental design with qualitative habitat assessments. The quantitative component involves a randomized controlled trial conducted on 30 building rooftops in a metropolitan city, with 10 replicates per green roof configuration—varying substrate depth (10cm, 20cm, and 30cm) and plant arrangements. Data collection instruments include thermocouples for temperature monitoring at hourly intervals over one year, along with biodiversity surveys conducted seasonally. Qualitative data are gathered through semi-structured interviews with landscape architects, building owners, and environmental policymakers to contextualize design choices and maintenance practices. Data from temperature sensors are analyzed using repeated measures ANOVA to determine statistically significant differences in thermal regulation, while biodiversity data are analyzed through species richness indices and multivariate ordination techniques such as Non-metric Multidimensional Scaling (NMDS). Thematic analysis will be employed to interpret interview transcripts, providing insight into the practical integration of green roof systems within urban planning. Expected findings suggest that increased substrate depth correlates positively with thermal mitigation capacity, with significant reductions in ambient rooftop temperatures (p < 0.05), and that plant diversity significantly enhances habitat complexity, fostering higher species richness (p < 0.01). Variations in irrigation regimes are anticipated to influence plant survival and biodiversity, informing optimal maintenance protocols. These findings will contribute to existing knowledge by empirically validating the efficacy of specific green roof designs in promoting thermal comfort and ecological benefits, filling gaps identified in prior literature regarding customizable green roof configurations suitable for diverse urban contexts. The study also develops a conceptual framework based on the Biodiversity and Urban Heat Island Mitigation Model, integrating ecological theory with urban sustainability practices. The main conclusion underscores that properly designed green roofs can substantially improve urban thermal environments and support biodiversity, emphasizing the need for tailored design strategies that consider local climatic, structural, and ecological contexts. Recommendations advocate for policy adjustments to incentivize green roof adoption, integration of biodiversity criteria into urban planning standards, and further longitudinal studies to assess long-term ecological impacts. Overall, this research offers actionable guidance for architects, urban planners, and policymakers seeking to leverage green infrastructure as a sustainable urban resilience strategy, and provides a validated methodological blueprint for future studies in green roof performance evaluation.