29 de abr. de 2009

$5.3 Million Green Roof Project Underway at Minneapolis Target Center

The New Roof Is Expected to Last40-50 Years
Created On: Tuesday, 28 Apr 2009, 3:46 PM CDT
Patrick Armijo
MINNEAPOLIS - Normally it’s the action on the floor of the Target Center that screams for attention, but to see the latest project underway you’ll have to look up. Crews are replacing the building’s roof with an environmentally-friendly green roof.
The project is not cheap. The city is paying $5.3 million dollars to create the largest green roof in the state of Minnesota. A conventional roof would have cost about $1.2 million, according to an estimate prepared for the city in 2008. But the green roof is expected to last much longer: up to 40-50 years, verses 20 years for a conventional roof.
Work started in March to change the old gravel roof into a green space. The new roof will be more energy efficient, and better retain storm water—saving the city through lower runoff utility fees. The roof should be complete this fall.
In debating the project, the Minneapolis City Council considered the lifespan of the building. The Target Center was built in 1991, and has already exceeded the median lifespan of 33.3 years for an NBA facility, according to a 2008 staff report. The lease with the Minnesota Timberwolves expires in 2025, 16-years after the new roof will be complete. In order to make the roof pay for itself in the end, the city will have to find a way to keep the Target Center in operation beyond 20-years. That makes the project an expensive gamble, but one city leaders ultimately decided was worth taking.
The Target Center has 30 different roof surfaces, with the main roof taking up 115,000 square feet. The new green cover will consist of several layers, including vegetation, water retention, and insulation.

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