Winter in the City
Wintertime in New York City: cold wind whips down the avenue and seems to follow you as you leave the frozen street and enter your building. The cold gust pulls the heat out of the lobby and even seems to follow you as you make your way up the building, whistling through the elevator shaft as it goes. The colder it gets outside, the worse it gets inside. Can’t somebody please make it stop? Is it too much to ask to be comfortable in your own lobby?
No, it is not too much to ask, and yes, we can help. It is 2016 and we have the technologies and expertise to better manage this all-too-common problem, but first we must examine what forces lay at the heart of the issue.
The Stack Effect
Wind coming in off the street is certainly a contributor, but once you get inside the building and the front door closes, this city-wide gust should be a non-factor, right? Then why do we still feel and hear this draft? The answer is, in a word, physics. When we provide heat to a building during the winter, the air within the building warms up. The common concept that heat rises is a bit of a misnomer; hot air rises because adding energy in the form of heat makes air less dense, more buoyant. This warm air is then displaced by heavier and denser cold air leaking in from outside, forcing the warm air to rise. Any holes or open windows in the top of the building allow this warm air to escape as the rush of cold air infiltrates the building envelope. We call this phenomenon the stack effect or, more descriptively, the chimney effect, because it acts on the exact same principle that allows a chimney to function. As long as there is a temperature gradient and holes at the top and bottom of a building, the stack effect will drive airflow, pulling air out of the lobby and sending it whistling up the elevator shafts during times of cold weather.
Adding to this phenomenon in many buildings is the interaction of ventilation systems, where a designed imbalance often allows more air to be exhausted from the building than is supplied. Buildings constructed prior to 2008 were built to an older code requiring considerably higher ventilation rates, which were often realized by increasing exhaust flows. A ventilation imbalance characterized by excessive exhaust rates can negatively pressurize a building and, acting like a building-sized vacuum, can literally suck air off the street. These systems can also lead to unpleasant odor transfer conditions or backdrafting of exhaust air. If whistling elevators, lobby comfort, or odor transfers are a problem of yours, the presence of an excessive exhaust imbalance can further exacerbate the issue.
Strategic Air Sealing Retrofits
So what can be done? Specific expertise in building envelope and ventilation system performance can be applied to minimize the impact that these forces can have on your living and working experience in a building. Strategic air sealing retrofits can better manage the stack effect and wind forces acting on and within a building, reducing the nuisance drafts. Specialized ventilation retrofits can work to minimize the total exhaust load in a building while bringing improved balance to the ventilation systems. By combining these technologies, buildings can be made more comfortable and less noisy, becoming more enjoyable places for you to live and work.
The team of Steven Winter Associates, Inc., Amatruda Engineering, LLC, and Northern Test and Balance Corp bring the experience required to offer turnkey solutions in combatting these frequently reported problems. If your building, or one you know, suffers from any of the symptoms described above, please contact us and we will be happy to give you a free consultation.