Which phenomenon increases with building height due to buoyancy effects, impacting air movement?

Which phenomenon increases with building height due to buoyancy effects, impacting air movement?

• A. Radiation
• B. Conduction
• C. Convection
• D. Stack Effect

Answer: (D)

Stack effect is the buoyancy-driven air movement that increases with building height. When indoor air is warmer than outdoor air, it becomes lighter and tends to rise, creating a pressure difference between the bottom and top of the building. This causes cooler outdoor air to be drawn in at lower levels and warmer indoor air to escape at higher levels. The taller the building, the larger this pressure difference, so the stronger the airflow through vertical openings like stairwells, shafts, and gaps. This movement influences infiltration and exfiltration, comfort, and energy use in multifamily buildings. It’s a specific form of buoyancy-driven flow tied to height, distinct from general convection, radiation, or conduction.

Stack effect is the buoyancy-driven air movement that increases with building height. When indoor air is warmer than outdoor air, it becomes lighter and tends to rise, creating a pressure difference between the bottom and top of the building. This causes cooler outdoor air to be drawn in at lower levels and warmer indoor air to escape at higher levels. The taller the building, the larger this pressure difference, so the stronger the airflow through vertical openings like stairwells, shafts, and gaps. This movement influences infiltration and exfiltration, comfort, and energy use in multifamily buildings. It’s a specific form of buoyancy-driven flow tied to height, distinct from general convection, radiation, or conduction.