Natural ventilation design is one of the most effective strategies for designing green buildings. The cost-effectiveness of this strategy should be considered to balance its benefits with its higher initial costs. In addition, it is becoming increasingly important to discuss the potential energy savings. For this purpose, quantitative evaluations are valued during the early stages of building planning and design because a building's shape can have large impacts on the performance of natural ventilation. However, few studies have fully examined the criteria for this type of evaluation. In this paper, a target air change rate is proposed as a desired criterion. The target air change rate is defined as the point where the gradient of the increase in the cooling effect from natural ventilation reaches a maximum. Above this point the rate of improvement in building comfort is more modest. In addition, this paper provides maps of indices for the United States. The maps help architects obtain a clear understanding of their design directions, e.g., a carefully designed natural ventilation strategy is highly recommended for building projects in warm-dry climates, where the internal gains are moderate, and for building projects in cold climates, where the internal gains are very high. (C) 2015 Elsevier Ltd. All rights reserved.