Water-Energy Related Aspect of Extensive Green Roofs: The Role of Evapotranspiration

Green roof technique has been intensely investigated in the last few years because of the several benefits it is believed to produce. Among the physical phenomena involved in a green cover, the evapotranspiration (ET) plays a cardinal role given its correlation both to hydrological and thermal balance of a vegetated surface. In this study a qualitative evaluation of the water lost through ET from two experimental extensive Green Roofs, by means of water content measurements, was performed. The associated latent heat was then calculated and compared to the solar radiation incident on the vegetated roofs surface. The analysis allowed to assess the importance of the ET in the Green Roofs thermal performance and to evaluate the influence of irrigation on the enhancement of this phenomenon.