Assessing the Impact of Green Roofs on Urban Heat Island Effect in Coastal Cities

Thesis Abstract

Urban areas, especially coastal cities, are increasingly experiencing intensified temperature elevations attributable to the urban heat island (UHI) effect, which exacerbates heat stress, energy consumption, and environmental degradation. The proliferation of traditional urban infrastructure, coupled with climate change impacts, underscores the urgent need to explore sustainable mitigation strategies. Green roofs have emerged as a promising intervention due to their potential to reduce ambient temperatures, improve air quality, and promote ecological resilience. Despite growing anecdotal evidence of their benefits, systematic empirical assessments of green roof effectiveness in coastal urban contexts remain limited, necessitating an in-depth investigation to inform urban planning and policy formulation. This study aims to evaluate the impact of green roofs on mitigating the UHI effect in coastal cities, with specific objectives to quantify temperature reductions attributable to green roofs, analyze the influence of green roof characteristics such as canopy density and soil depth on thermal performance, and develop predictive models for urban temperature modulation. The research is anchored on the premise that green roofs can significantly attenuate surface and ambient temperatures, thereby mitigating the UHI phenomenon in coastal urban environments. Employing a mixed-methods research design, the study combines quantitative field measurements with qualitative assessments. The quantitative component involves a comparative analysis of temperature data collected from a sample of 50 green roofs and 50 conventional roofs across the metropolis, utilizing high-resolution infrared thermography and data loggers over a 12-month period to capture seasonal variations. The qualitative component entails structured interviews with urban planners, landscape architects, and residents to gain insights into the social and institutional factors influencing green roof adoption and performance. The population of the study encompasses commercial and residential buildings within the city’s central business district and surrounding neighborhoods known for high UHI intensity. Data collection instruments include calibrated infrared thermographic cameras, digital environmental sensors, and semi-structured interview guides. The validity and reliability of these instruments are ensured through calibration protocols, pilot testing, and inter-rater reliability assessments for qualitative data. Quantitative data will be analyzed using statistical techniques such as multiple regression analysis and ANOVA to determine the relationship between green roof characteristics and temperature variations, while thematic analysis will be applied to qualitative interview transcripts to explore stakeholders’ perceptions and policy implications. The anticipated findings suggest that green roofs can facilitate a temperature reduction range of 2 to 5°C on surface and ambient levels, with performance moderated by factors such as vegetation type, soil moisture content, and roof age. The analysis is expected to reveal statistically significant correlations between specific green roof attributes and thermal mitigation effectiveness, supporting the development of predictive models based on the Theory of Ecosystem Services and Urban Climate Adaptation Frameworks. These models will enable urban planners to optimize green roof design for climate resilience. This research contributes to the body of knowledge by providing empirical evidence of the thermal benefits of green roofs in coastal city settings and by developing a comprehensive understanding of the interplay between green infrastructure design and urban microclimates. It offers practical insights for policymakers, urban developers, and environmentalists aiming to integrate green roofs into climate change adaptation strategies, with suggested guidelines for maximizing their effectiveness. The study concludes that green roofs are a viable and cost-effective approach to mitigating the UHI effect in coastal cities. It recommends the promotion of green roof adoption through policy incentives, public awareness campaigns, and integration into building codes. Further research is suggested to explore long-term performance, economic assessments, and the synergy between green roofs and other urban cooling interventions to foster sustainable urban development in climate-vulnerable coastal regions.