The green rooftop at the Target Center is complete. And aside from
being Minnesota's biggest green roof and the first green roof installed
on a U.S. arena, this green roof will capture more than a million gallons
of stormwater per year and help keep Minnesota water bodies healthy.
The 113,000 sq. ft. roof is nearly three acres and is made up of sedum and Minnesota prairie plants, like lupine, wild strawberry, and dotted blazing-star.
How does a green roof keep a big building energy-efficient and earth-friendly? “A green roof can cut energy use in the summer by as much as 40 percent,” says Corrie Zoll, founder and president of the Minnesota Green Roofs Council.
One reason is because it reduces urban heat islands and the temperature of roofs—just think of how hot black asphalt gets in July. And it increases something called evapotransporation, which is the transfer of moisture from the roof’s soil and plants, instead of letting rooftops get baked like a lone ginger snap and forcing overworked air conditioners to crank and wheeze as a result.
Green roofs also help to create a healthy eco-system. "With much of the city covered in asphalt, green roofs can also help to soak up the storm-water run-off that would otherwise end up in the river,” Zoll adds. Green roofs help reduce the large amount of stormwater runoff that would otherwise get heated by the asphalt, pour out into the street and pick up petro-chemicals along the way, and then drain into the Mississippi, causing its temperature to rise and the wildlife to suffer.
In St. Paul, plans are underway to green the roof of the St. Paul fire station on West Seventh. The rooftop, which will have public access, will measure approximately 9,000 sq. ft. and is expected to be complete before 2010. The fire station project is part of a citywide initiative to protect water quality and to reduce volume discharge, the amount of heated stormwater flowing directly into the Mississippi.
The Target Center's green roof will last 40 years, reduce heating and cooling needs by as much as 40 percent, and is expected to hold annually as much as one million gallons of stormwater that would otherwise pick up asphalt heat, debris, and chemicals and pollute the already health-challenged Mississippi.