Mitigating the Urban Heat Island Effect by Light and Thin Rooftop Greening

Abstract

A main enumeration was carried out for mitigating the urban heat island effect by light and thin rooftop greening at the existent building. Six kinds of light and thin rooftop greening systems were installed on the existent building roof, and those heat characteristic and heat balance were analyzed. Surface temperature of the non-greening area was the highest, 60°C. Surface temperature of greening area was 30-35°C in the time when the irrigation was done regularly, and it was 35-45°C in the time when the irrigation was reduced. About accumulated evapotranspiration, in the time when the irrigation was reduced, Grass area was about 3kg/m&sup2, but Sedum Mexicanum Britton area was 0.4-2.0 kg/m&sup2. The results of heat balance analysis show the latent heat consumption of evapotranspiration at greening system to prevent increase sensible heat. It became clear that light and thin rooftop greening had effect of mitigating the urban heat island effect from the above result. It confirmed that mitigating the urban heat island effect by rooftop greening varied in the kind of plant, water condition and so on.