Fighting Stack Effect: Winter Tips from Mechanical Engineer A. Frantz

Jan 31, 2020 11:07:11 AM


Solutions for Maintaining Occupant Comfort this Winter

In the depths of winter, there’s nothing nicer than escaping from the wind and cold into a warm building. Unfortunately, sometimes winter creeps from the outdoors into lobbies, causing discomfort for occupants and sometimes freezing pipes. However, don’t be fooled. Your heating system is not always to blame. Consider Stack Effect.

If you’ve ever lit a fireplace, you’ll know that hot air rises up the chimney and cold air is drawn from every corner of the house towards the hearth. Most high rise buildings don’t have chimneys, but they do have something similar: stairwells and elevators shafts. As warm air rises up these shafts, the lowest floors become negatively pressurized, sucking in cold air. Unfortunately, we can’t fight the laws of physics – this negative pressure will always be present in winter on tall buildings. Luckily, there are several ways to fight the chill:

  • Vestibules are your friend. Instead of opening the door and hitting the lobby with an icy blast, put two doors in a row. This prevents the momentary direct opening between indoors and outdoors, and is required for many new buildings by energy code.
  • Revolving doors achieve the same result as vestibules– instead of a blast of cold air when the door is opened, it’s just a little puff.
  • Insist on tight construction. Even with vestibules, negative pressure pulls air in through windowsills, door jambs, and cracks in walls. The older the building, the worse this effect tends to be.
  • Place tight doors between your elevator lobby and the reception area. Even sliding doors can help.
  • Modern HVAC systems can adjust themselves automatically in the winter, providing additional heated make-up air when needed to fight the pressure.
  • Dedicated cabinet unit heaters in vestibules helps eliminate drafts before they reach the indoors.
  • Placing lobby return air openings close to the ground helps draw warm air down away from the ceiling, which can be particularly important in tall lobbies.
  • Fighting Stack Effect usually requires a combination of these approaches. Our experts at Peter Basso Associates are here to help you find the right solutions for your building that will maximize comfort, while minimizing cost!

Aaron Frantz, PE is a mechanical engineer for Peter Basso Associate’s, Corporate and Governmental building group.

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