Green roofs mitigate heat stress and other environmental challenges in urban areas. Irrigation of green roofs is beneficial of the roof plants and the thermal performance. Nevertheless, few studies on irrigation of green roofs exist and the practice is often considered unsustainable. The new green roof research facility in Dresden provides a monitoring system for coupled water, heat and matter fluxes in green roofs. Grey water is recycled in the system, pre-treated in a constructed wetland and used for irrigation. 21 test beds provide observations on the impact of shading, plant development and selection, irrigation intensity and type of substrate. The system configuration and sensor selection are described. A preliminary simulation of heat budget in irrigated and non-irrigated green roofs demonstrates the cooling effect of evaporative latent heat for the irrigated system. We highlight potential future research directions, follow an open data policy and encourage cooperative research and academic teaching on site.