Effect of irrigation on the experimental thermal performance of a green roof in a semi-warm climate in Mexico

A study of the experimental thermal performance of a green roof in a semi-warm climate of Mexico, which considers the irrigation effect, is presented. The experiment was performed in two stages. The first stage consisted of selecting from among five types of plants, commonly used in green roofs, the one that tolerates the greatest number of days without irrigation. This stage was carried out in the warm season and we selected the Aeonium subplanum plant for the thermal experimental evaluation. In the second stage, we constructed two test cells in which the temperature and the heat flux of a green roof and a concrete roof were measured for a period of 8 days. During the experimental test the green roof was watered in one day of the evaluation period. From the results, it was found that after the irrigation event the maximum temperature of the green roof components is reduced by 6.4, 4.8 and 1.3° C for vegetation, substrate and slab, respectively. The experimental results show that the use of a green roof decreased the temperature by 20.5 °C compared to a concrete roof. The test cell with green roof had an accumulated electricity consumption 1.3 kWh lower than the test cell with the conventional roof, representing 10.3% less electricity consumption.