Abstract
The heat island phenomenon in urban areas has become a problem in the recent years. One measure to overcome this, which has been attracting attention, is painting the cool roof with a paint that has high solar reflectance. However, the solar reflectance has been reported to decrease over time owing to staining from the paint. Our investigations reveal that a self-cleaning paint, based on an acrylic silicone polymer, is effective in maintaining a high solar reflectance and preventing dirt from adhering. These evaluations have been conducted on the cool roof of an actual building by conducting a pollution test under outdoor exposure conditions. In this study, we investigated an accelerated aging test and reported the results. ASTM D7897-15 (ASTM method) is an accelerated pollution test method for cool roofs, which has been established in the United States. In Japan, a similar accelerated pollution test method exists for antifouling civil engineering materials introduced by the Public Works Research Institute in Japan (PWRI method). The ASTM method and PWRI method were compared by conducting a stain acceleration test using a self-cleaning- and conventional-type cool-roof coating. The substitutability of the exposure test, correlation with the exposure test, performance evaluation of the paint, and the effect of the difference in the pretreatment conditions were verified. The results of these tests were reported.
Highlights
Cool-roof coatings have received considerable attention worldwide as a solution for the “heat island” effect in urban areas
The self-cleaning-type goodretention results even in the difference is solar reflectance andpaint solarshowed reflectance of the exposure test in months) It was considered that the hydrophilic layer on the surface of the self-cleaning-type paint causes less adherence illustrated in Figures 9 and 10
There was a small decrease in the reflectance of the self-cleaning-type of pollutants; the adhered are washed by rainwater
Summary
Cool-roof coatings have received considerable attention worldwide as a solution for the “heat island” effect in urban areas. The effects of cool-roof coatings and the reduction in the air-conditioning load have been studied [1,2,3,4,5,6]. It has been pointed out that the solar reflectance of cool-roof coatings decreases shortly after installation [10,11,12,13,14,15]. The decrease in the solar reflectance is due to the soiling of the coating, chemical–physical modifications, and biological growth. Various studies on evaluation methods for cool-roof coatings have been carried out [16,17]. The reduction in reflectance has been studied in exposure tests using various materials. In Japan, the main component of soil is carbon; it has been reported that, after
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