Yizhi Zhang

As urban areas grow and face climate-related challenges, rooftop greenhouses (RTGs) offer a promising approach for Controlled Environment Agriculture (CEA) to enhance urban food production while providing potential energy-saving benefits. However, the energy performance of RTGs integrated with mid-rise residential buildings, which represent a substantial proportion of the existing urban housing stock in cold climates, remains poorly understood. This study investigated the influence of RTG integration on the energy demand and indoor thermal conditions of a four-story residential building across cold-climate regions. Dynamic simulations using IDA-ICE were performed to analyze the influence of different glazing and shading configurations, comparing rooftop and ground-based greenhouse scenarios and host building performance. RTG integration reduced the host building’s annual heating demand by 6.2–7.6%, with thermal buffering primarily benefiting the top floor, where heating demand decreased by up to 24.2%, while lower floors remained largely unaffected. No summertime overheating risks were observed. Compared to a ground-based greenhouse, the RTG had a lower heating energy use by 2.8–14.6% depending on glazing and shading configuration, by using free heat from the host building. This study highlights the potential of RTG integration as a passive energy-saving measure, while supporting sustainable urban food production, contributing to more sustainable and climate-resilient cities.

Urban agriculture has been increasingly recognized as a strategy to improve food system sustainability and reduce the environmental impacts associated with food production. Among various forms of urban agriculture, rooftop greenhouses have attracted increasing attention due to their ability to integrate food production with building systems, creating opportunities for energy savings and improved resource efficiency. However, the environmental performance of rooftop greenhouses remains insufficiently understood. Existing studies are limited in number, often focus on specific case studies, and employ diverse life cycle assessment methodologies, making comparisons across studies difficult. This report systematically compiles and reviews existing environmental performance of rooftop greenhouses, with a particular focus on life cycle assessment approaches. The review examines reported climate impacts, resource use intensity, and environmental benefits associated with rooftop greenhouses, while critically evaluating methodological choices related to goal and scope definition, system boundaries, functional units, inventory data, and impact assessment. The findings indicate that environmental performance is highly context-dependent and strongly influenced by methodological assumptions. Conventional life cycle assessment approaches often fail to capture the dynamic interactions between greenhouse operations, crop growth processes, and host buildings, resulting in an incomplete representation of environmental performance. To address these limitations, we argue that rooftop greenhouses must be conceptualized as building-integrated systems rather than standalone agricultural units. A framework for integrated system-based assessment combining life cycle assessment with dynamic simulation approaches can support more robust evaluations of rooftop greenhouses and contribute to the development of climate-efficient and resource-efficient urban food systems.