Bioclimatic approach gives attention to the design of roof since it is commonly the building element which is most exposed. Some of the most favorable roof cooling techniques are roof ponds which appear to influence the thermal behavior of roof through different processes including evaporation, radiation and conduction. Large air-conditioning energy savings were estimated, reaching 100% in a variety of locations. In this paper, the most known types of roof ponds are presented, including uncovered and covered with or without sprays, energy roof (water contained within pa-paret), coolpool (open pond shaded by sloping louvers), coolroof (with floating insulation), walkable pond with night water circulation (insulation embedded within the pond), wet gunny bags (with a "floating" wetted cloth) and ventilated roof pond. This study provides the background to, and the current status of, all the above as passive cooling technique capable of providing both reduction of energy demand and thermal comfort. After an extensive background statement giving the history and motivation to create different types of ponds, the basic advances and disadvantages are sketched, focused on the comparative performance of the presented techniques. Several researchers have measured the energy reductions caused by different types of roof ponds in a variety of locations and have also suggested simulation techniques. In the presentation of each method, the basic principles have been recalled underlined the time and space scale of its application and analyzed its accuracy and suitability for use in different type of environments. The specific problems of each method are underlined focused on the environmental principles and design considerations. A condensed account of roof pond experience in a number of climates is being presented, including numerical results. Finally discussion and conclusions have been presented, focused attention on the most interesting new guidelines for research on the measurement and estimation of roof ponds.
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