The Cool Roof Experimenting with Change of Color to Cool the Roof

Document Type : علمی - پژوهشی


Lecturer, Faculty of Architecture and Urban Planning, Shahid Beheshti University


In Iran, some 22 percent of the building energy dissipates through the roof. In the hot arid parts of the country, most of this energy is used for cooling rather than heating. There are several methods for reducing this energy loss. Insulation is one popular method throughout the world. A more effective method is to reduce the energy penetrating the building by means of cooling the roof. There are three main techniques for obtaining a “cool roof”. In the first method, heat loads are reduced by lightening the color of the roof, hence increasing its albedo. In the second method, the “green roof”, the roof is suffused with vegetation, which is more expensive and technically complicated. In the third method, the roof is sprinkled with water. In this method, a significant amount of water is wasted, however. Because of its inexpensiveness and simplicity, the first method was chosen for an experiment, in which part of a dark green roof was repainted with brilliant light green. The daily summer temperatures were then measured on an hourly basis and compared with the shaded areas of the roof as well as areas covered by plants. The results indicated that the repainted areas were about 17 percent cooler.

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