For the same opening area, a taller, narrower windows promotes somewhat higher natural ventilation than a shorter, wider one. The reasons behind this is as follow:
- Stack Effect
Warm air, being less dense, rises and creates a vertical pressure difference (dP); drawing cool air in at lower levels and exhausting warm air at upper levels. - Increased Airflow
A larger pressure differential (dP) drives greater airflow through the opening. Thus, for the same area, a taller window provides higher ventilation efficiency due to its greater H/W ratio. - Pressure Differential (dP)
The pressure difference increases with the vertical distance between the inlet and outlet; a taller opening produces a greater separation between high-pressure (lower) and low-pressure (upper) zones.
Related notes:
Natural ventilation – Floor area to be ventilated
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