# Stack Effect Stack Effect

There are several constructed objects that can make the stack effect such as a stairwell, atrium, elevator shaft, laundry chute, dumbwaiter, and a skylight shaft. However, the most common form of the stack effect takes place in a chimney.

The stack effect is a natural form of ventilation and is driven by buoyancy. Buoyancy is simply what happens when air rises because of the difference in the temperature and moisture when the inside is compared to the outside.

How to Calculate Driving Force for the Stack Effect

The driving force of the stack effect is the difference in the air pressure from the outside of the building to the inside. This can only apply to buildings where it’s assumed that there is air both inside and outside of the building in question. It is calculated as P = C*a*h(1/To-1/Ti)

Where:

• P = pressure difference
• C = .0188
• a = atmospheric pressure (Pa)
• h = height of the building in meters
• To = Temperature outside in Kelvin
• Ti = Temperature inside in Kelvin