Green roofs cool cities, clean the air, provide habitat, and manage stormwater. They are compelling tools to teach interconnected human-ecological systems. This study included the design, pilot, and evaluation of a fourth-grade science unit entitled “Raising the Green Roof”, exploring these connections. Five classrooms in two Midwestern U.S. public elementary schools participated, and 4th-grade students (n = 73) drew systems models at three time points (212 models) and wrote their ideas. Qualitative content analyses of the models showed that learners were increasingly combining social systems (green roof infrastructure) with ecological systems (water cycle) across the unit. Students also increasingly evidenced specific knowledge as they progressed through the unit. The analysis of student models revealed that most student confusion is related to built environment aspects (e.g., how water moves from building roofs to municipal waterways). Results of the study suggest the potential for teaching socio-hydrologic systems thinking at the fourth-grade level. The findings emphasize the need to enhance built environment education for youth in science units that aspire to connect features of the built environment, such as green roofs, with ecology. The study additionally reinforced the effectiveness of place-based units in elementary education that emphasize science practices.