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Green Roof, Clean Water

Milwaukee Public Library
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Innovation Summary

The Milwaukee Public Library constructed a green roof ensemble including an observation deck, 30,000 square feet of plantings and substructure and 132 solar panels. The complementary Green Ideas Area on the first floor provides information on practical conservation and renewable energy techniques adaptable to home and business use.

Problem Statement

The roof above the 1957 addition to Milwaukee Public Library’s Central Library was scheduled to be replaced in 2009. The anticipated cost of replacing the roof with another conventional roof was $700,000. In 2005, Mayor Tom Barrett called on City departments to reduce energy consumption by 15% and to promote effective green infrastructure solutions to the city’s storm water management challenges. Recognizing the value of a green roof in promoting the Mayor’s goals, the administrative team of MPL proposed replacing the conventional roof with a green roof and adding solar panels. While the green roof was more expensive initially, it was estimated to last at least twice as long and provide energy savings of $438,345 over 40 years. The roof of the addition had been built to support an additional floor of library use if MPL chose to build “up”, so it was structurally strong enough to withstand the weight of a water-saturated green roof. The proposal required approval by elected officials and other City departments. Outside funding was sought to support the project. The City provided $950,000 through the Capital budget. Additional money came from grants and incentives from the Metropolitan Milwaukee Sewerage District (MMSD), the City’s Energy Challenge Fund, We Energies and Focus on Energy. Besides providing a sound roof for the structure, the project also needed to meet the requirements of the various funders supporting the project. MMSD’s contributions enhanced the project with educational components. The Green Ideas Area and the observation deck on the green roof showcase the feasibility and value of green roofs. Practical adaptations of technology are explained to reduce polluted storm water runoff and reduce stress on the sewer system. The total cost of the roof, panels and educational components came to $1.5 million


The green roof installation began in fall 2009. Two educational opportunities were developed along with the green roof project; the Green Ideas Area and staff guided tours to the roof. The Green Ideas Area (GIA) on the first floor of the library is accessible whenever the library is open. The GIA includes visual and printed material to explain and encourage the use of renewable energy and resource conservation techniques. A continuously played video shows the installation of the library’s green roof, solar panels and the deck. The area also includes a monitor which relays real time and historical data on the production of energy by the solar array and information on solar energy. The Green Ideas Area provides practical information for adapting green roof, solar and resource conservation techniques to home and business use. Additional green technology projects in Milwaukee could fuel the local economy and support job growth. From Earth Day through October informational tours are provided to the green roof. A floating deck on the green roof, composed of recycled and man-made materials, can accommodate 20-30 visitors. Trained librarians known as “roof rangers” explain the structure and purpose of the roof, emphasizing the positive impact of absorbent surfaces on the watershed and suggesting practical home applications of the technology. The growing medium and plants absorb 40 to 90% of rainfalls and delay the flow of excess rainwater into the combined sewer system for between 45 minutes to 4 hours, alleviating stress on the system. The plants absorb up to 80% of the sun’s radiation reducing the urban heat island effect. The solar panels provide about 1% of the energy needed by the library. The energy is not stored and used onsite but is converted from dc to ac, metered for credit and sent to the power grid.


The green roof and Green Ideas Area are entering the third year of use. Public tours are scheduled three times each week mid-April through October and special tours are available. Visitors leave with an understanding of the fiscal and environmental benefits of the green roof and the value of absorbent plantings to the environment. A brief explanation of the solar panels is given along with an outline of the financial benefits to the library and city. General information adaptable to home use is provided in a great setting and in a conversational way supporting the Library’s educational mission. Use of this information can impact the quality of the watershed and reduce overflows. The green roof has proven to be a magnet for activity in the library. Marquette University’s Engineering Outreach Summer Program brought over 100 well-prepared students to the roof. Attendees at the International City/County Management Association Convention in Milwaukee and Department of Natural Resources agents from around the State of Wisconsin are among the groups who have toured the roof. The Milwaukee Metropolitan Sewerage District has brought businesses in to see the roof. Families from Poland, China and around the country have read about it and come to see it. The Milwaukee Public Museum and the Library are offering a joint program on the Transit of Venus, using the green roof deck as a staging place for telescopes. On a lighter note, a young man proposed to his future wife on the green roof’s deck and it’s a popular spot for tweets and blogging. The Library has created another destination in downtown Milwaukee, supported City goals to reduce energy consumption and preserve the watershed and fostered resource conservation. The library has provided attractive and appealing ways to educate the public on environmental literacy. The view is great too.