A novel hydroponic roof system for the energy renovation of flat roofs in the Mediterranean area

This study introduces and validates a novel Deep Water Culture hydroponic roof system as a building-integrated solution for enhancing indoor thermal conditions and energy efficiency in Mediterranean climates. Unlike conventional green roofs, the proposed system removes the soil layer and uses a water-based nutrient solution that simultaneously supports plant growth and acts as a thermal energy buffer. A full-scale prototype was experimentally tested on an existing office building in Catania (Italy); based on the experimental data, transient thermal modelling is then undertaken with TRNSYS to simulate the prototype with different roof configurations. Results show that the hydroponic roof reduces indoor peak temperatures by up to 2.8 °C in the summer, increases them by 2.4 °C in the winter and shifts heat flux peaks by up to 16 h. Annual simulations indicate energy savings of 47% for space cooling and 51% for space heating, too. The DWC hydroponic roof demonstrates strong potential as a relatively lightweight, passive retrofit technology combining urban agriculture and building decarbonization.