Raising The Green Roof: Why More Big-City Businesses Are Putting Plants Up Top

On a hot summer's day, steamy, concrete-laden New York City streets can be 7 degrees warmer than the surrounding suburbs and rural communities. As night falls, these 'heat island' temperatures can really roast urban dwellers – at times the sheet-drenching, sleepless summer nights in NYC are more than 20 degrees hotter than in the more verdant, less concreted areas nearby.

Even walking becomes a sweaty chore, as pedestrians, without the shade of a tree, trudge through windless streets with the warm exhaust of vehicles or hot air blown from A/C units. Sufferers at street level may think they have it bad, but what about the climate up on the city's rooftops?

Fuggedaboutit: The temperature on a sun-soaked asphalt roof in New York can top out near 190 degrees Fahrenheit. Black-top roofs are also a strain on the city's sewage and drain systems – since dark roofs absorb little to none of the city's rainwater, propelling tsunamis of runoff into storm drains – clogging sewer lines, pooling water and causing innocent bystanders... to suffer the gutter splashes from thoughtless cars.

Chemical engineer and Low and Bonar CEO Brett Simpson says he's on a mission to change this old ecosystem. He wants to shift the pace at which cities move around their water, air and even the birds and bees – and he's hoping he can do all this.. with a few more high-tech roof mats.

His company's lightweight 'Xero Flor' green roofing mats are on the largest green roof in America, which is about 8 football fields worth of short, green shrubbery perched atop a Ford truck plant in Dearborn, Michigan. But not all his green installations are so massive: some 9,000 square feet of terraced areas on the pointy Empire State Building have more recently gone green, too. You can't see much of this rooftop transformation happening from the ground, but Simpson says that up on the roof, business is good:

“What we're seeing is quite a healthy expansion in the use of green roofs.” Simpson says, citing his green roof business growing at roughly 10-15% a year in the U.S. “People see that not only does this make environmental sense, but it actually makes good business sense.”

Thirsty green roof plantings are good for lightening the water load on municipal city drains, but they're even better for reducing the draining energy costs on big industrial buildings. At the Ford plant, the crisp, green blanket of low shrubs that's been on the roof since 2003 still helps keep the heating and cooling bills low. In the chilly winter months, the extra layers keep the place 10 degrees warmer, while in the summertime, the short, knotty rooftop carpet makes the temperature inside the Michigan auto plant 10 degrees cooler.

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