The Impact of Green Roof Conversion on Energy Efficiency: A Case Study of KTU Kanuni Campus

Green roofs are multi-layered systems constructed on a supporting structure, with the vegetation layer forming the uppermost layer. They contribute to ecological, economic, and social sustainability through functions such as rainwater harvesting, reduction of heat loss, mitigation of the urban heat island effect, and the creation of aesthetically appealing public spaces. University campuses—key environments for implementing sustainability principles—play a crucial role in energy management, circular resource utilisation, and water management. In this context, this study investigates the impact of converting the hard-surfaced roof of the “Surveying Engineering Canteen” at Karadeniz Technical University’s Kanuni Campus into a green roof. Following field surveys and feasibility assessments, three inverted green roof alternatives (extensive, semi-intensive, and intensive) were modelled in DesignBuilder to evaluate energy performance, operational and embodied carbon, construction costs, and the additional structural load resulting from the soil’s water retention capacity. The findings indicate that green roof applications reduce annual heating loads by 36–46%, improve indoor operative temperatures during winter months, and lower operational carbon emissions by 16–20%. However, embodied carbon and construction costs increase relative to the existing roof, particularly for semi-intensive and intensive systems. Structural load analysis revealed that while extensive roofs fall within acceptable limits, semi-intensive and intensive systems may exceed standard live-load thresholds due to their higher water retention loads, requiring reinforcement. Overall, the extensive system emerges as the most feasible option in terms of cost, embodied carbon, and structural compatibility, while still providing meaningful energy savings and environmental benefits.