In this paper, a wet porous cooling plate has been utilized for building wall. Cooling can be achieved due to the evaporation in the porous plate. A mathematical model on the heat and mass transfer in the unsaturated porous media is developed to analyze the influences of ambient conditions and the porous plate thickness on the cooling performance of the porous evaporative plate. With a decreasing in ambient relative humidity and an increasing in ambient temperature, more cooling of the porous evaporative plate can be supplied for the inside of room. The heat exchange between the inside surface of the porous plate and the air in the room should be intensified to achieve a higher cooling efficiency of the porous plate. The ambient wind speed and the thickness of porous plate also have significance influences on the average temperature of the porous plate. All these results should be taken into account for the utilization of the porous evaporative cooling plate. (C) 2011 Elsevier Ltd. All rights reserved.