CHICAGO (CBS) -- Efforts to conserve energy at high-rises have led to an increase in falling ice, which Chicagoans have been ducking as they walk downtown.
Illinois Institute of Technology architecture professor Antony Wood, who also heads the Council on Tall Buildings and Urban Habitat, said highly insulated windows allow wet snow to stick on the cold sides of high-rise buildings.
Wood said snow and ice would just slide off single-pane windows of older buildings before building up to any significant size.
Roman Stangl, founder of Northern Microclimate, said the situation can be handled, but it takes careful engineering. His Canadian consulting firm specializes in advising high-rise architects how to avoid designing buildings that drop ice on passersby.
Stangl said systems that blow warm air over window surfaces will prevent snow and ice buildup.
Warmed-up windows – along with adjustments to the color, shape and slope of architectural details where snow accumulates – also can reduce ice buildup.
Stangl also said, while falling ice signs outside high-rises are nice, they're hardly the last word about the danger of falling ice.
"Ice and snow that will fall off a building – especially a high-rise – has a good chance of fluttering and floating in the wind, and actually landing somewhere across the street. So there is no really, really safe place to stand or to walk," he said.
Robert Clifford, senior partner at Clifford Law offices, said the signs might be a nice public service, but any suggestion protect building management from liability is just "nonsense."
Clifford said the signs are meaningless legally, especially in Loop buildings that have had regular problems with falling ice.
"The law is very clear," he said. "The owner of a building, as well as the owner of an establishment that you might be coming out of – such as a restaurant – if they have knowledge that there are known propensities for falling ice, they have to take greater steps to protect their patrons and the public."
Clifford said a better protective measure than falling ice would be architectural features to contain ice, or divert it to an area where it can't fall on someone's head.
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