Passive cooling with a hybrid green roof for extreme climates

In a warming planet, overheating is becoming an increasingly important issue at all latitudes and locations, even in areas which traditionally did not have this problem. Passive cooling systems improve thermal comfort in a hot climate using a fraction of the energy used by conventional mechanical systems. This paper investigates the performance of a novel passive cooling system, a hybrid green roof and verifies its cooling potential, through test beds, in a hot climate in Southern California. The hybrid green roof combines evaporative cooling with a radiant system integrated in the green roof to improve its cooling performance. The concept is then implemented in projects under development in hotclimates in the United States, Middle East and Asia. In these projects additional passive strategies are sometimes combined with the hybrid green roof to substantially improve outdoor and indoor thermal comfort in an extreme climate withminimal use of mechanical cooling.