Two multi-functional voids were planned to enable total outside air cooling in the building where there is considerable internal heat generation and the cooling period is long by utilizing two multi-functional voids. The voids were designed as ventilation towers for supply air and exhaust air, and planned to install a barrier between the openings of both voids on the rooftop. Two voids were located under consideration of the regular wind direction and the effect of separation flow on the rooftop to avoid short-circuit between supply air and exhaust air. From the result of the air flow analysis using CFD and field measurement, it can be confirmed that exhaust air containing pollutant or tracer-gas from the exhaust air void do not move to the supply air void.

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The authors outline the knowledge they have gained through their design experience on the efficacy of natural ventilation in non-residential buildings in Japan. They also describe the various challenges which must be overcome to deploy natural ventilation. It is hoped that the knowledge presented in this paper will be of reference in the drafting of guidelines for the research and design of future natural ventilation systems. Natural ventilation yields great energy-saving effects, but it is also necessary to make reference to and examine the numerous challenges which must be overcome at all stages from design to operation, with reference to actual conditions in Japan, and indicate the necessity of developing methods for verifying the performance of natural ventilation.