Assessing the Impact of Green Roofs on Building Energy Performance in Urban Environments

Thesis Abstract

The rapid urbanization experienced globally has intensified the demand for sustainable building solutions that mitigate energy consumption and enhance urban resilience. Green roofs have emerged as a promising strategy to improve building environmental performance by providing insulation, reducing heat island effects, and enhancing overall energy efficiency. However, empirical quantification of their impact on building energy performance in diverse urban contexts remains limited, necessitating rigorous field-based assessments to inform sustainable urban development policies. This study aims to evaluate the extent to which green roofs influence the energy performance of commercial and residential buildings in metropolitan areas, with specific objectives to quantify energy savings attributable to green roofs, analyze the variation in thermal comfort levels, and identify key factors influencing performance effectiveness. The overarching goal is to develop an evidence-based framework for integrating green roofs into urban building design practices to optimize energy efficiency. A comparative case study research design was adopted, involving six buildings equipped with green roofs and six comparable buildings without green roofs, selected across the city to control for confounding variables such as building age, size, and usage type. The population comprised 12 urban buildings operational for at least five years, with the sample size determined by purposive sampling to ensure representative diversity. Data collection instruments included sub-metering for energy consumption, thermal imaging cameras, and occupant surveys to gather quantitative and qualitative data. Additionally, meteorological data were obtained from local weather stations to contextualize energy performance metrics. Data analysis was performed using a combination of descriptive statistics, multiple regression analysis, and t-tests to compare energy consumption and thermal comfort levels between buildings with and without green roofs. Regression models assessed the relationship between green roof characteristics (e.g., substrate depth, vegetation type) and energy savings. Thematic analysis was applied to occupant feedback to understand perceived thermal comfort benefits. Validity and reliability of instruments were ensured through calibration of measurement devices and pilot testing of survey questionnaires. Expected findings indicate that buildings with green roofs demonstrate significant reductions in cooling and heating energy usage, averaging 20-30% savings, especially during peak summer months. Further, occupants in green roof buildings report higher thermal comfort levels, corroborating instrumented data. The analytical framework anticipates revealing that green roof effectiveness is moderated by factors such as roof age, maintenance regimes, and plant species selection. These insights are expected to contribute to refining building codes and urban planning guidelines to incentivize green roof adoption. The study's contribution lies in providing rigorous, context-specific empirical evidence on the energy-saving potential of green roofs in urban environments, expanding the theoretical understanding of sustainable building performance, and informing policymakers and practitioners on optimal green roof implementation strategies. The findings support the application of the Technological Acceptance Model and the Energy Performance Gap framework to examine user acceptance and actual energy performance. In conclusion, the research advocates for integrating green roofs as a standard sustainable measure in urban building design, emphasizing the need for comprehensive policy incentives and capacity-building initiatives. Recommendations include developing standardized green roof performance metrics, extending research to include lifecycle analyses, and fostering collaborative efforts among urban planners, architects, and environmental engineers to promote widespread adoption. Future studies should explore long-term performance, scalability issues, and the socio-economic implications of green roof integration in diverse urban landscapes.