Cities turn to green roofs to protect the environment


Milwaukee has been in the news recently as it moves ahead with plans to remove residential sources from the city’s sewer system in the hope rain water will soak into the soil and prevent sewage overflows into Lake Michigan.

Flooding is an issue for many cities in these days of increasing urbanization, so the search is on for ways to control runoff.

To prevent runoff flooding, cities around the world are adding requirements for permeable pavement and green roofs to building codes.

Green roofs are in favor right now since they moderate air temperature, improve air quality and control runoff.

Chicago was an early green-roof booster, but now these roofs are mandated throughout much of the world.

Denver, which ranks eighth highest in the U.S. in particulate and ozone pollution and is one of the worst heat islands in the U.S., has embraced green roofs.

There, any new construction of over 25,000 square feet requires solar panels or a green roof, and when older structures require new roofing, the same standards apply.

The city estimates that these green roofs add about $15 a square foot to the cost of roof installations, but the payback comes in about six years since heating and cooling costs are lower.

The green roof itself lasts longer, too, since it’s protected by the plants and soil.

Toronto has some of the most stringent green roof standards in North America, requiring all roofs on industrial, commercial and residential builds more than six stories high to have a portion covered by plants.

The city, on the shore of Lake Ontario where the water table is high, has flooded frequently in recent years as its population — and pavement — has soared.

Fortunately, the city is home to the University of Toronto’s GRIT (Green Roof Innovation Testing) Lab. Its research is driving the development of more efficient green roofs.

GRIT is an interdisciplinary research center.

Civil and mechanical engineers, biologists, architects and landscape architects all work on the green roof issue.

Their focus is on developing a green roof to fit any circumstance.

Roofs that collect and store maximum amounts of water where runoff is an issue are different from installations that absorb maximum heat to control surrounding temperatures. In areas with green belts, roofs return water directly to the soil.

Right now GRIT is researching the kinds of plants and soils best suited to integrate solar panels into effective green roofs.

That adds power generation to the climate control positives of the new generation of city roofs.

Twenty-five years ago when we purchased our Port home we followed new city rules to stop our roof runoff from entering the sewer system.

Twenty years ago we decided to get some use out of our roof and put solar panels on top of the house.

Back then, installing a green roof didn’t seem practical, especially given how the load from our hip roof was supported inside the house.

But the next owner of the house may find more and better options both for paving and roof-top climate control, part of the ongoing effort to keep the world green and growing.



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Ozaukee Press

Wisconsin’s largest paid circulation community weekly newspaper. Serving Port Washington, Saukville, Grafton, Fredonia, Belgium, as well as Ozaukee County government. Locally owned and printed in Port Washington, Wisconsin.

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Port Washington, WI 53074
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