EMPHASIS IN THIS CHAPTER is on moisture transport via ven tilation and air infiltration. When calculations are made as to the relative importance of the various moisture transport mechanisms, air movement normally heads the list. In the case of convection versus diffusion, a 10 to 1 ratio (or even higher) is not surprising. Therefore, it is necessary to understand what air movements are present in our buildings and what moisture problems are a direct result of these air movements. In the following sections, the relationship between ventilation requirements, natural flows of air, and key building locations will be discussed with regard to how they influence building moisture problems.