Openings located low and high, and on opposite sides of a space, create a ‘stack effect’ – warm indoor air rising out through high openings, drawing in cooler outdoor air through low openings.

Using the air’s buoyancy resulting from a difference in its temperature – climates with a minimum 1.7°C (3°F) difference between indoor and outdoor temperatures – the stack effect in a space, or within a ventilation shaft, will induce an air current that removes hot air from a space or building.

Guidelines for locating inlet and outlet openings:

  • Residential spaces – a minimum of 3 meters (10 feet) apart in height.
  • Commercial spaces – a minimum of 4.6 meters (15 feet) apart in height.

The greater the height between openings, the greater the air movement. Locate inlet openings below the height of an occupants’ upper body – 0.76 m to 1.37 m (2½ ft. to 4½ ft.) above finished floor.

For more detailed information and calculations, see In-Depth Information Pages under Tools + Resources.