Experimental investigation of the thermal and optical behavior of an intensive green roof system installed in an office building in Athens

The aim of this paper is to experimentally investigate and analyze the thermal and optical behavior of a Green Roof System (GRS) installed in the 10000 m2 roof of a fully insulated, bioclimatic office building in Peania. More specifically, during the experimental procedure, measurements of the outdoor temperature and relative humidity have been performed, as well as of the air temperature inside the building and the surface temperature of the ceiling. Furthermore, the surface temperatures of the roof were measured using thermographic imaging, as well as the optical properties such as the albedo of the roof’s covering materials. The GRS is an intensive green roof and it consists of almost 16000 indigenous plants of at least 14 different kinds which cover the largest part of the roof surface. The rest of the area is covered by a running truck of made by a bioclimatic stabilized ceramic floor. The ceramic material was found to be 5.1⁰C – 7.2 ⁰C cooler than the soil or other common materials and the planted area 10.1 ⁰C - 16.1 ⁰C cooler than the ceramic floor. The different species of plants were also studied and the conclusion that the density of the foliage plays a primary role was extracted, as there was a difference of 11.8 ⁰C between a plant with and a plant without dense foliage. It was observed that the different surfaces present their maximum temperature at different hours. The ceramic floor, at 14:00 for the 46.7% of the time and at 15:00 for the 40 %, while the planted area at 14:00 for the 53.3 % of the days, at 13:00 for the 26.6% and, oppositely to the ceramic floor, never at 15:00.