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Installation work begins on Minnesota's largest green roof

Installation work begins on Minnesota's largest green roof

August 11, 2010

Installation of the 2.5 acre green roof vegetation on the City-owned Target Center begins today. Over the course of two days a 165 ton crane will hoist five truckloads of plant material, which includes 900 rolls of pre-grown vegetated mats of sedum and native plants for installation on top of the arena's main roof. More than 540 cu yards of soil is being blown onto the rooftop between 120’– 165’ in the air, using a blower truck. The roof is the largest green roof in Minnesota and, at the time of design, the fifth largest green roof in the United States.

The green roof is installed on a state-of-the-art waterproofing membrane which includes a leak detection system called Electro Field Vector Mapping (EFVM). The membrane will help withstand constant dampness, high alkalinity, and exposure to plant roots, fungi, and bacterial organisms as well as varying hydrostatic pressures.

The green roof features a 2.75” growing zone in the center of the main arena roof structure and a deeper 3.5” growing zone around the perimeter where the structural capacity is greater to maximize storm water retention and plant vigor. The pre-grown mat of sedum and native plants creates the base of the green roof system and will be complemented by additional plantings of plants native to Minnesota’s prairies once the roof is installed to enhance plant diversity and ecological resilience.

To complete the roof by Fall 2009, 11 miles of sustainable, water-efficient irrigation lines will be installed and 14,000 concrete pavers for firebreaks and roof protection will be laid.

Green roofs provide ecological benefits by reducing the negative effects of hard surfaces like traditional roofs on stormwater quality, volume, rate, and temperature on the receiving waterbody, in this case, the Mississippi River. At 113,000 square feet, almost 3 acres, this green roof has potential for mitigating stormwater runoff from a significant amount of impervious surface in a downtown location where space does not permit use of other Low Impact Development Techniques to mitigate for the negative effects of hard surfaces on receiving waterbodies. Positive impacts on local water bodies are valuable in a City that prides itself on its legendary waterbodies: The City of Lakes in the Land of 10,000 Lakes.

Benefits of a green roof include capturing stormwater, which has a positive impact on the Mississippi River. Runoff can include pollution and trash from buildings and other hard services, which makes its way into our waterways.

The green roof design team includes Leo A Daly, Kestrel Design Group, and Inspec; locally-operated Stock Roofing, a Tecta America company, is replacing all of the roofs on the Target Center and installing the extensive green roof.

While the project called for 50% recycling of materials, the Tecta team has set its own goal of 100%, resulting in an estimated 450 tons of existing rock and 590 tons of existing pavers, 140 tons of existing roofing membrane, and more than 60 truckloads of existing roof insulation.

The installation and ongoing maintenance of the green roof is the last stage of a necessary roof replacement project that also includes replacing all 29 smaller roofs on five levels. The cost of roof replacement for all 30 roofs is $5.32 million and is paid for using a set-aside capital fund for improvements.

The public may view the installation of the Target Center green roof from the cam capturing the construction of the Twins Ballpark.
LEO A DALY is an international architecture, planning, engineering, interior design and program management firm with 1100 professionals in 30 offices worldwide. The firm has a 40-year history in designing sustainable buildings including the award winning Gold LEED® regional headquarters for the National Park Service in Omaha, NE, and is currently designing a platinum LEED® building in Doha, Qatar.  LEO A DALY's Minneapolis office comprises 134 professionals and it is currently completing 12 sustainable buildings, aimed at Silver LEED for the U.S. Army at Fort Carson near Colorado Springs.

About Kestrel Design Group
The Kestrel Design Group is a Minneapolis-based, sustainable landscape architecture firm specializing in green roofs, living walls, storm water and urban trees and sustainable site solutions. An emerging leader in both green roof technology and tree cell technology, it co-authored Minnesota's Sustainable Building Guidelines and The Minnesota Soil Bioengineering Handbook. Its recent green roof projects include Minneapolis City Hall, the Minneapolis Central Library, Edgewater Condominiums and the Green Institute/Phillips Eco-Enterprise Center.

About Inspec
INSPEC, Inc. is an engineering/architectural firm specializing in roof, exterior wall, pavement and waterproofing design, construction observation, and management services. It employs more than 65 engineers, architects, project managers, technicians, and office support in offices located in Minneapolis, Milwaukee, and Chicago. Inspec has been providing sustainable roofing, waterproofing, and other building envelope solutions for over 35 years. The firm has completed over 40 projects in which the waterproofing membrane has a vegetated or otherwise landscaped overburden.

About Stock Roofing, a Tecta America Company
The Stock Roofing Company, LLC. was founded in 1987 Warren Stock, a small business owner and operator in Minneapolis, Minnesota. For nearly twenty years, Stock Roofing has grown in capacity and capability to meet the residential and commercial roofing needs of the Twin Cities metropolitan and surrounding areas. In 2003, Stock Roofing Company, LLC. joined Tecta America Corp.

About Tecta America Corp.
Tecta America Corp., headquartered in Skokie, IL, is the largest commercial roofing company in the U.S. and provides roofing solutions nationwide with over 50 locations and more than 3,500 employees. Services include roof installation, roof replacement, new construction, disaster response, repair, restoration, maintenance, full service national roofing management and, through its Tecta ES [Environmental Solutions] division, green roof systems, photovoltaic systems, and day lighting systems.


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