An environmentally friendly alternative device, called hydrosolar roof, designed for heat dissipation in buildings has been integrated into a standard air conditioning system. To perform an energy consumption optimization it has been necessary to include all the elements in a global model. Then, three main subsystems have been considered: cooling machine, hydraulic network and hydrosolar roof. A description of the three subsystems is done and the mathematical model is presented. The cooling machine thermodynamic model has been carried out using EES (engineering equation solver). The hydraulic network model has piping, pump and nozzle information. The hydrosolar roof direct contact heat and mass transfer simulation has been developed with a CFD code. Special attention has been paid on the cooling efficiency. The global model has been applied to a real prototype facility experimentally tested. All the energy consumptions have been calculated for different pumping heads. A global coefficient of performance (COP) has been defined and the optimum value obtained. (c) 2005 Elsevier Ltd. All rights reserved.