What is Stack Effect?

The stack effect happens, when warm air moves or flow upwards in the building.

In summer, the warm air rises because it is lighter than cold air. So when it rises, it escapes out of the upper levels of the building through ventilation openings, windows or leakages. The rising warm air reduces the pressure at the base of the building, forcing cold air to infiltrate through either open doors, windows, or other openings and leakage in lower levels of the building.

Stack Effect
Must Read: All You Know About Ventilation

The stack effect generally causes air infiltration.


In other words, it is a convection effect arising from temperature or vapour pressure difference (or both) between outside and inside of the room and the difference of height between the outlet and inlet openings.

Stack Effect - Different Forms of Ventilation

How does Well Stack Ventilation Work?

For ventilation, a high ceiling is required. The effectiveness of this type of natural ventilation depends on the size of the building. If the building ceiling is not high, warm air actually will not move away from the inhabitants.

Other factors such as, the amount of heat in the building, shape of the building itself, the orientation of the building whether it is wind ward side face or not, etc.

In short, stack effect ventilation can make a huge difference in the facility. By directing warm air away from the building personnel, escape through the roof, we are giving a huge impact on the interior conditions of the building.

Satck Effect Ventilation

Pros & Cons of Stack Ventilation:

  • It does not require blowing air.
  • Relies on the natural elements like, temperature & Gravity.
  • It does not involve operating costs & cooling is inexpensive.
  • It does not consume energy.
  • It cannot completely control temperature.
  • The impact depends on exterior temperatures.
  • Can bring polluted air into buildings.
Also Read: Types of Ventilation

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Comments (2)

  1. Hi.
    Please I was planning on changing the window sizes to bigger ones initially but I want to know if the combination of extractor fans and rotating turbines can help with temperature reduction on production floors as the heat generated by the machines is very much.

    1. Thank you for contacting us!
      Opening doors and windows as well as other openings can improve circulation, let hot air escape and lower the temperature of the building. Opening higher windows works well to remove hot air, because warmer air rises. When you give hot air a place to escape, it will naturally rise up, leave the building and be replaced with cooler air.
      In your case, you can combine both systems, as the rotation turbine is not that effective individually.
      Note: –
      Factory/Warehouse required 15 air change per hour.
      Calculate the required cubic feet per limit (cfm) to decide the no. of extractor fan. Must consult the local retailer of extractor fan.
      Here is a four-step process on how to calculate the room CFM:
      Step 1 – Use the above Air Changes per Hour Table to identify the required air changes needed for the use of the room. Let’s say factory requiring 15 air changes per hour.
      Step 2 – Calculate the volume of the room (L’xW’xH’).
      Step 3 – Multiply the volume of the room by the required room air changes.
      Step 4 – Divide the answer by 60 minutes per Hour to find the required room CFM:
      Using this formula, you can know the required cfm for your room & you can get a clear idea on how many exhausts are needed.
      Hope this will be helpful to you!
      Thank You!

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