Assessing the Impact of Green Roofs on Building Energy Efficiency and Indoor Comfort

Thesis Abstract

The increasing global demand for sustainable building solutions has intensified interest in green roofs as an innovative approach to enhancing urban building performance, particularly in relation to energy efficiency and indoor environmental quality. Despite numerous studies exploring various aspects of green roof implementation, there remains a paucity of comprehensive empirical evidence quantifying their actual impact on building energy consumption and occupant comfort within real-world contexts. This study seeks to empirically assess the extent to which green roofs influence energy efficiency and indoor thermal comfort by conducting a field-based investigation across thirty residential and commercial buildings in metropolitan areas. The primary aim is to determine the effectiveness of green roofs in reducing cooling and heating loads while improving occupant comfort levels. Specific objectives include to (1) measure and compare energy consumption patterns between buildings with and without green roofs over a 12-month period; (2) evaluate indoor thermal comfort parameters through occupant surveys and environmental monitoring; (3) analyze the relationship between green roof characteristics such as depth, coverage, and plant species, and their impact on energy and comfort metrics; and (4) develop a predictive model incorporating key variables to quantify green roof benefits. The research adopts a mixed-methods approach, integrating quantitative analysis of energy consumption data and indoor environmental measurements with qualitative insights obtained through structured occupant questionnaires. The study employs a quasi-experimental research design, with data collected from a stratified random sample of 15 green roof-equipped buildings and 15 comparable non-green roof buildings. Structural data on green roof features and building characteristics are obtained via site surveys and document reviews, while energy consumption data are collected from utility meters over a one-year period. Indoor temperature, humidity, and CO2 levels are monitored using calibrated environmental sensors, complemented by occupant surveys to assess comfort perception. The validity of environmental data is ensured through calibration and repeated measurements; reliability is established via pilot testing questionnaires and inter-rater assessments. Data analysis involves descriptive statistics, independent samples t-tests, and ANOVA to identify significant differences in energy use and comfort levels. Multiple regression analysis is employed to examine the influence of green roof variables on energy savings and indoor thermal comfort. Structural Equation Modeling (SEM) is used to explore causal relationships and test the conceptual model hypothesizing that green roof characteristics mediate between building type and occupant comfort outcomes. The theoretical framework is grounded in the Sustainable Building theories and the Thermo-Environmental Model, which explain the mechanisms through which green roofs modify building thermal behavior. Expected findings indicate a statistically significant reduction in cooling and heating energy consumption, averaging around 15-20% compared to non-green roof buildings, along with improved indoor thermal comfort as evidenced by higher occupant satisfaction scores and more stable indoor environmental parameters. The study anticipates identifying specific green roof features—such as depth and plant diversity—that most strongly influence energy savings and comfort levels. These findings will fill critical gaps in the existing literature by providing rigorous empirical evidence from a diverse sample of buildings with varied green roof configurations in urban settings. This research contributes to the scientific understanding of green roofs' efficacy, offering concrete data to inform sustainable building design and policy development. It also proposes a practical model for predicting energy and comfort benefits associated with green roofs, serving as a decision-support tool for architects, engineers, and building owners. The study concludes with targeted recommendations for optimizing green roof design, policy incentives for green infrastructure adoption, and avenues for future research, such as long-term performance assessment and integration with renewable energy systems.