Cross ventilation relies on wind to force cool exterior air into the building through an inlet (window, door, etc.) and to force warm interior air out of the building through an outlet (window, door, etc.).
As one would expect, a window's orientation to the direction of wind movement is critical to the amount of air flowing through an inlet. As a rule-of-thumb, an inlet is useful for cross ventilation if the direction of wind flow is in the range of -45 degrees to 45 degrees to the surface normal of the window. Energy Scheming operates under this assumption. Of course, one can manipulate exterior geometries to redirect air movement through a window:
Also of importance to cross ventilation is inlet and outlet area. The amount of heat removed from a building is directly proportional to the inlet and outlet areas.
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