The impact of natural ventilation of a roof cavity on improvement of the thermal environment and reduction of cooling load of a factory building is discussed A computer program was developed with the logic in a companion paper [1] to observe the effect of cavity ventilation on the operative temperature of the occupied zone in the factory Comparisons were made between factories with a cavity roof and a single roof in the Japanese climate Results showed that the cavity roof was superior to the single roof in lowering the operative temperature by about 44 C When the factory was air conditioned the cooling load reduction reached approximately 50% during the summer to maintain an operative temperature of 26 C Results showed that a naturally ventilated cavity roof has excellent potential for improving the indoor thermal environment and energy savings of factory buildings without complicated cooling installations and life time power consumption (C) 2010 Elsevier B V All rights reserved