Traversing New York after a snowstorm is no easy task. The threats of slush puddles and curbside snowbanks have pedestrians paying close attention to the sidewalks and pavements, fearing a soaked shoe or a twisted ankle. But there is another wintertime hazard that's never far from New Yorkers' minds: falling ice.
The thought of being hit on the head by a frozen projectile falling from a Manhattan skyscraper is terrifying, to say the least. As new high-rises continue to change the city's skyline, the danger of falling ice increases. While there is no public data on the number of injuries or deaths associated with the hazard, every winter there are reports of injuries resulting from ice falling off of buildings in New York. You can look to St. Petersburg, Russia during the winter of 2010 for a sense of the devastation that falling ice can create—five people were killed and more than 150 were injured by falling icicles that season.
It can be hard to wrap your head around what causes ice to plummet off of buildings, but research points to a few key factors. From contemporary building design to innovations in energy-efficiency, engineers and architects have had trouble with mitigating the risks of ice falling from modern skyscrapers.
Energy-efficient buildings are promoting dangerous ice formations
A 2012 paper published in the International Journal on Tall Buildings and Urban Habitat looked into the causes and potential solutions for ice falling from skyscrapers in northern regions. The report points to one interesting culprit in the formation of dangerous ice and snow on buildings: innovations in energy-efficiency. Building that are either built to be energy-efficient or are retrofitted for such release heat at a significantly lesser rate than buildings that have not. This leads to a colder temperature on the exterior of the building, which in turn allows for ice and snow to have a freeze fest on the roof and facade in lieu of melting.
"The currently achieved reductions in heat loss from many buildings' interiors are promoting an increase in potentially dangerous ice and snow formations," the report says. "As insulation values, glass technology and building systems progress in the future to conserve energy, the corresponding further reductions in heat loss through the facade will only increase the probability of hazardous ice and snow formation."
Energy-efficient buildings have had major impacts in the reduction of carbon emissions in some of the world's largest cities, but that is apparently a double-edged, icy sword. Go figure.
Contemporary design isn't helping the issue
The report also cites advancements in design technologies as a key cause in high-rise ice hazards. As engineers and architects continue to figure out how to build stunning facades, ledges and other features more than 1,000 feet off the ground, the risk of ice and snow formations increases. Ice can even form on top of buildings when it seems like a perfectly mild day on the ground. According to the report, in-cloud icing at relatively high altitudes regularly occurs on skyscrapers (it isn't much different from the type of icing that happens on airplanes). When that ice builds up on precarious ledges and sides of buildings, it can fall from dangerous heights—even when it's above freezing at ground level.
Preventing ice formations on buildings is not easy
While there is no specific language requiring property owners to clear ice off of their buildings, New York's Administrative Code does require that they maintain a "safe condition for all parts of the building." But when it comes to preventing dangerous ice chunks from plummeting from a structure, solutions are not easy (or cheap). One big issue is that falling ice is not a major concern for engineers and architects when they design a building. Mitigating dangerous ice on buildings often requires design modifications or add-on features, both of which are ugly and expensive.
At the end of the day, ice is going to fall from New York's skyscrapers—stopping such would require a lot of work that simply isn't worth the cost. But at the end of the day, the chances of being clunked by a plummeting piece of ice are quite slim, and there are much more dangerous things to worry about in the city. So continue worrying about the slush puddles, New York. You can actually see those coming.