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Spending Through the Roof

Posted by Content Coordinator on Thursday, March 19th, 2015


An Old Problem

Figure 1: In winter, warm air escaping through openings in the roof mean that cold air is drawn into the bottom of the building.New York City Fire Department and New York State regulations require openings at the top of elevator shafts and stairwells in many tall multifamily buildings and hotels. Originally meant to improve fire safety by drawing smoke out of the building, changes in building construction and firefighting practice mean these vents are needlessly open all the time. Today, they mostly serve as big unwanted holes, passing heated air out the top all winter (Figure 1). When you open the front door to your building, the cold blast you feel is air rushing in to replace the air leaking out the top and chilling the entire lobby.

Buildings with open elevator vents lose heated air at a staggering rate in the winter. Elevator vents alone will leak about a living room’s worth of warm air every minute. This leakage has both financial and environmental costs. All the air that escapes through open vents is replaced with cold air from outside, which then needs to be warmed by the building’s heating system. That means that 4–16% of heating fuel is being used to heat the outdoors, most of which can be saved by fixing these holes.

A 15-story multifamily building in a dense city block loses $3,000 through the roof each heating season.6 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. And in a less dense area, that bill increases to $13,000. The How-To Guide on page 10 shows how to estimate the savings potential from closing these vents.

A Citywide Issue

What are the citywide effects of this wasted energy? There are approximately 4,000 multifamily buildings in NYC that are at least 10 stories tall—the threshold where heat loss through vents really starts to make an impact on energy bills. Assuming that 80% of these have open vents, the amount of heated air wasted each year could fill 29,000 Empire State Buildings.

When thousands of lobbies lose their warm air, thousands of boilers must kick on and heat the cold air that’s come in to replace it—with a cumulative energy impact predicted at over 460 billion BTUs annually, equivalent to 80,000 barrels of oil. This means that every year, building owners and tenants are paying over $11 million in unnecessary heating costs citywide.

This energy expense has an environmental cost as well. About 30,000 metric tons of carbon dioxide equivalent (CO2e) are needlessly released into the atmosphere each year from this wasted heat. If these vents are left open until 2050, over 1 million metric tons of CO2e will be emitted. This is equivalent to the annual energy use of over 90,000 homes. Capturing “low-hanging fruit” like these simple fixes is necessary to reach citywide carbon reduction goals, as described in One City: Built to Last, NYC’s plan to reduce greenhouse gas emissions 80% by 20509 and in 90 by 50, Urban Green’s comparable study.

Figure 2: Building height and density comparison

The amount of heated air wasted each year could fill 29,000 Empire State Buildings.

Download full version (PDF): Spending Through the Roof

About the Urban Green Council
Urban Green Council is the New York Chapter of the U.S. Green Building Council (USGBC). Our mission is to advance the sustainability of urban buildings through education, advocacy and research…A non-profit organization established in 2002, Urban Green is funded by contributions from foundations, its members, and corporate sponsors. Our in-house experts and a dedicated network of volunteers are helping to transform the built environment in New York City with models that can be replicated in urban centers nationwide.

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