Stack effect exists in all buildings that are at a different temperature to that outdoors. Stack effect can be:
- A nuisance - e.g. whistling noises and/or cold drafts;
- Offer operational challenges - e.g. keeping lobbies warm, elevator doors that do not close and/or increased energy costs; or
- Impose a danger to people - e.g. slamming doors and/or doors that cannot be opened.
Stack effect pressures on doors can exceed 0.8" H2O / 200 Pa and result in airflows through open doors that exceed 2000 fpm / 10 m/s. Stack effect exists in buildings that are in both hot and cold climates although the impacts and resultant mitigation techniques are different for each type.
As buildings are getting taller, the strength of stack effect is becoming greater. By way of example, stack effect in some of the tallest buildings can exceed 3.5” H2O / 750 Pa. That is the pressure just created by indoor / outdoor temperature differences. Unfortunately, there are some misconceptions about how and why stack effect exists. This then leads to incorrect efforts to mitigate / fix. Further, the design community does not have a consistent design practice from jurisdiction to jurisdiction. The method of ventilating apartments in Toronto, NYC and Chicago let alone the UK and China can be different and each requires a different thought process to get right.
The purpose of this presentation is to provide a bit of background on stack effect and present some real life examples of stack effect in tall buildings as well as the impact it has on people in their place of work and home. This will be presented through:
- A quick description of the physics of stack effect – stack effect does not happen because hot air rises;
- A series of case studies with data collected on different buildings;
- Anecdotes and descriptions of the experience of the building occupants; and
- Descriptions of means through which adverse consequences were mitigated.
The objective is to offer insight on how stack effect can adversely impact people, the severity of that impact and consequences for owners and designers. Design strategies will be offered. The examples presented will include tall buildings in both hot and cold climates. The impact of wind and the HVAC system on the overall building pressures will be presented and discussed and used to describe how a building can experience a combination of look-alike problems.
- Develop a greater understanding of the physics of stack effect.
- Learn the relative pressure forces that wind and stack effect can impose.
- Understanding of some real world examples and design strategies for the future.
- Appreciate the difference between heating and cooling mode stack effect issues.
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