- The vertical airflow within buildings caused by temperature differences between the building interior and exterior.
- Movement of air or other gas in a vertical enclosure (e.g., duct, chimney, building), induced by the density difference between the air or other gas in the enclosure and the ambient atmosphere. Note: Stack effect is a significant concern in heating system design for tall buildings in cold climates. Sometimes referred to as “Chimney Effect.”
- Pressure difference caused by the difference in density between indoor and outdoor air due to an indoor/outdoor temperature difference.
- Movement of air into and out of buildings, chimneys, flue gas stacks, or other containers and is driven by buoyancy. Buoyancy occurs due to a difference in indoor to outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the "chimney effect," and it helps drive natural ventilation and infiltration.