Stack Effect
What is the stack effect?
The stack effect, also known as the chimney effect takes place in tall towers.
In extreme cold climate, as those encountered in central Europe, north America or northeast Asia during the winter time, it corresponds to the natural convection of cold air from the bottom to the top of a building. The pressure differential generated by the stack effect increases with the temperature differential (between the outside and the inside) and the height of the tower.
Conversely, reversed stack effect occurs in extreme warm climates, like in the summertime in the Middle East region for example.
Consequences of the Stack effect
The stack effect may result with severe consequences for the safety of occupants and serviceability of high-rise buildings if not addressed adequately, that include:
- Annoying whistling of air in the elevator and staircase shafts, doors and envelop gaps
- Failure to operate doors (incl. Elevators and staircase doors) due to high pressure differentials, with the risk of casualties in case of emergency evacuation
- Faster propagation of smoke and fire
- Cracking of internal partition walls
- Odor and contaminated air flowing from the bottom of the building to the top premium apartments*
- Appearance of mold due to excess of humidity at the top part of the building*
- Poor energy management with overheated upper floors and conversely uncomfortable cold lower levels.*
(* applies to cold climates, opposite in warm ones)
Our Approach
The study of stack effects proceeds in two steps:
First of all, a preliminary design review to determine the likelihood of appearance of pressure differentials based on the building height, local weather conditions, interior partitioning, and facade design.
Depending on the above conclusions, a detailed assessment of the stack effect phenomenon is conducted. Together with our technical experts, possible mitigation measures and design adjustments are proposed and tested in order to improve the design and comply with local building regulations.
Mitigation Measures
- Improvement of the air tightness of the building facade, and internal doors.
- Horizontal and vertical separations within the building
- Installation of Pressure relief valves or Modifications of door types
- Pressurization of the elevator and stairwell shafts, lobbies and hallways
Benefits
Whether at the early design stage or after the construction of a high-rise building, there are numerous benefits in assessing the stack effect issues:
- Support the compliance of the design with regards to comfort and fire safety before the planning authorities
- Improvement of air quality
- Safer emergency evacuation
- Better occupant comfort
- Increased energy efficiency of the building
