The experiment was conducted on the rooftop of the Main Research Building at the Building Research Institute. The building used as a subject was a 7-story RC-made building; the rooftop finish was asphalt roofing. Table 1 shows the outline of the test pieces. Two cases were assumed; one with the test section of asphalt roofing (AR, hereafter) only, and another with that of water-permeable tile (ceramic), perforated bricks (red bricks) and artificial turf (polyethylene resin). The test piece was installed directly on the rooftop slab. Based on the unit of 300x300mm, a 300mm interval was placed between individual test pieces to prevent any influence of the adjacent section.

From the three standpoints of "latent heat of evaporation,” "ventilation” and "solar reflection”, three types of passive cooling methods were applied: (a) watered AR surface

(Case 2 ~ 5), (b) ceramic tiles with and without water content (Case 6, 7) and (c) perforated bricks with and without a coat of white paint (Case 8, 9). In cases of (a), to compare the cooling effect at the time of sprinkling, we did a 0.5mm sprinkling once a day in the morning, noon or evening (8:00, 12:00 or 16:00) or three times a day (morning, noon and evening). In the preliminary test, when the amount of sprinkling exceeded 0.5mm, the AR surface overflowed. Thus, we set the one-time sprinkling amount to 0.5mm. In cases of (b), after soaking ceramic tiles for two hours, we placed them with a 30% volume water content in the test section in the evening (18:00, September 2). In cases of (c), white paint was painted on the surface. The temperature (Tn) at the upper test piece in (b) and (c) corresponds to the rooftop surface temperature when the test piece is used as a rooftop finish. However, in this study, we expressed Tn as the upper test piece temperature in order to distinguish it from Case 1~5, in which no test piece was installed. We regarded T| in Case 1 as the non­measure rooftop surface temperature. We then regarded the fact that Ti, Tii, and Тш had decreased compared to that surface temperature in other cases of different surface finishes and of similar insulation structure as the cooling effect.

The total measurement period was one week from September 1 to 7, 2003. Main measurement items were the rooftop surface temperature (Tab.1, Ti), upper test piece temperature (Tab.1, Tii), lower test piece temperature (Tab.1, Тш), outside temperature and solar radiation. The outdoor temperature was measured at the Assmann’s aspiration psychrometer (approximately 1.2m in height). For other temperature measurements, we used the Type-E thermocouple and recorded the results at 10-minute intervals. For general meteorological data such as wind direction, wind velocity and rainfall, we utilized the measured values from the nearest local weather station.