Investigating and analyzing the thermal behavior of the “green roof system” installedin two buildings in Athens, Greece

The present paper deals with the experimental analysis and monitoring of the energy and environmental performanceof a green roof system installed in two residences,in the region of Athens, Greece. The one is located in municipality of Psichico and the other in municipality of Peristeri. The analysis was carried out in two phases.During the first phase, monitoring of the green roof systemwas performed. Extended surface and temperature measurements were taken of the indoor and outdoor environmentwhere the green roof is installed.During the second phase, in order to investigate the potentialof energy saving the heating and cooling loads were calculated using the dynamic thermal simulation software TRNSYS.Lower surface temperatures are measured in the spaces, which are covered by vegetation while higher in the spaces, which are not covered by vegetation. Surfaces that are covered externally with the green roof have lower U-values than conventional roofs without any vegetation, resulting in reduced heat losses from the interiorof the building.The energy performance evaluation showed a significantreduction of the cooling load in the case of the residence in Psichico (11%), while the reduction of the cooling load in the case of the residence in Peristeri is insignificant (2%). This can be justified by the fact that, in the case of the residence in Psichico, the whole roof is covered by the green roof system, while in the case of the building in Peristeri, only some parts are covered. Finally, the influence of the green roof system in the buildings heating load was found to be insignificant.