COMPARATIVE SUMMER THERMAL AND COOLING LOAD PERFORMANCE OF NATURAL VENTILATION OF CAVITY ROOF UNDER THREE DIFFERENT CLIMATE ZONES

This paper presents the benefit of natural ventilation of a roof cavity to reduce summer thermal loads ofa factory and, therefore, the cooling load due to air-conditioning systems with respect to various climatezones in Japan. A simulation program was developed to analyze the impact of cavity ventilation on theoperative temperatures of the occupied zones in a factory. Three climate zones in Japan: cold region(Sapporo), temperate hot-humid region (Tokyo), and subtropical region (Naha) were selected forcomparison. In an air-conditioning mode, two calculations of cooling loads were made. In one of thecalculations, the factories were supposed to be air-conditioned whenever the operative temperaturewas higher than 26oC. In the other calculation, the air-conditioning was operated only during theworking hours. Results show that the cavity roof factory was superior to the single roof factory inlowering operative temperature. In a cold region, the presence of natural ventilation of a cavity roofallowed the factory operated under natural ventilation in most of summer time while in the hotterregions, the application of cavity roof showed an excellent potential for reducing energy cooling loads.