Home Air Quality Report Examines Magnitude of Elevator Shaft Vent Heat Loss, Offers Solutions

Report Examines Magnitude of Elevator Shaft Vent Heat Loss, Offers Solutions

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NEW YORK—Buildings of at least 10 stories in height have the most potential to suffer from the chimney effect if rooftop vents are open at the top of elevator shafts. The chimney effect occurs when heated air is given an opportunity to escape through a rooftop. This can add costs, of course, as makeup air coming into the building through the lobby must be heated. According to Grant Salmon, Deputy Director, Steven Winter Associates, New York, the taller the building, the greater the chimney effect. “In a taller building there is greater pressure,” he says. “The temperature differential also impacts the pressure.” Exposure to wind can accelerate the effect and “tight” buildings can be impacted more.

In some cities, New York for example, elevator shaft vents have been required to remain open to improve fire safety. According to a report prepared by Urban Green Council for the New York State Energy Research and Development Authority (NYSERDA), however, a 2014 change to the New York City Building Code allows new solutions. The report is entitled, “Spending Through the Roof.”

One solution is to cover two-thirds of the vent with annealed glass, and leave the rest open. The second solution is to install a motorized set of louvers that will remain completely closed until there is a fire, when the alarm system or a smoke detector will open them.

According to the report, the first option is best for smaller, simpler buildings, and can be installed inexpensively in-house by building maintenance staff. The cost ranges from $500 to $2,000 per vent, depending on the in-house capabilities of building staff, with a simple payback period of less than one year, depending on the details of installation.

Solution for Larger Buildings

With the second option, the motorized louvers, the total vent area can be covered as long as the louvers will open upon detection of smoke, loss of power, or manual override. This requires electricity and access to the fire system, so the project will need to be overseen by a qualified engineer or contractor to ensure that all code requirements are met. This solution is best for larger, more sophisticated buildings. The cost can range between $5,000 to $15,000 per vent, depending on access to the various systems and other site-specific concerns. Although it’s a pricier solution, the payback period is similarly short (one to five years depending on the details of the installation) and will save significant money in the long term.

For the Spending Through the Roof report, hotels and multifamily buildings were studied. According to research and analysis performed by engineers at Steven Winter Associates, a 15-story multifamily building in a dense city block loses $3,000 through the roof each heating season. Where buildings are farther apart, greater exposure to wind increases the airflow, more than doubling the cost to $6,500. The taller the building, the more air is lost through the same size hole. A close-packed 30-story building wastes $6,000 each winter. In a less dense area, that bill increases to $13,000.

According to the study, the 4,000 ten-story and above buildings in New York City, assuming 80 percent have open elevator shaft vents, waste the equivalent of 29,000 Empire State Buildings of heated air each year. About 30,000 metric tons of carbon dioxide equivalent are needlessly released into the atmosphere each year from this wasted heat.

Other Areas to Check for Leakage

According to the report, closing up open elevator shaft rooftop vents is just one step one can take to address leakage in a building. Additional areas to focus on include windows, doors and mechanical equipment. Addressing leakage will not only reduce costs and help the environment; it will improve guest and associate comfort levels as well.

Interestingly, it is not only heated buildings that can suffer from a chimney-like effect. Steven Winter Associates’ Salmon says air-conditioned buildings can experience a reverse chimney effect when there are open rooftop vents and cold air falls to the bottom of the building and gets replaced by the warm air coming in from the rooftop. “There are numerous buildings in Florida that have been closing their vents for humidity concerns,” Salmon says.   

Spending Through the Roof includes steps showing how to assess a building’s potential energy savings from addressing open elevator shaft vents. The report also includes a brief summary of the technical study of 15 buildings performed by Steven Winter Associates. To access the complete study, click here.

Glenn Hasek can be reached at editor@greenlodgingnews.com.

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