An experimental method to quantitatively analyse the effect of thermal insulation thickness on the summer performance of a vertical green wall

tGreen fac¸ades and walls greatly contribute to reducing solar gains and dispersion through the buildingenvelope. This implies a lower energy load for both heating and cooling and the mitigation of thermal con-ditions in outdoor areas. Despite this, more studies are needed regarding the influence of these systemson the thermal behaviour of insulated fac¸ ades. In this manuscript, we report the results of experimentalresearch carried out on a vertical green wall in a continental Mediterranean climate. The main goal ofthe research is to establish a thickness above which the behaviour of the green fac¸ ade becomes isother-mal and its performance do not improve. To this end, we analyze and evaluate the effect of insulationthickness on the energy performance of a green wall using a new methodology called green fac¸ ade opti-mization (GFO). Comparing the simulations to experimental data, collected in a full-scale experimentalbox during the summers of 2011 and 2012, allowed the model to be validated. The results show that agreen wall acts as a passive cooling system when the fac¸ ade is moderately insulated, up to an insulationthickness of 9 cm, above which more insulation becomes redundant and inefficient.