Milwaukee Public Library Green Roof

When the existing leaky roof of the beaux arts Central Public Library’s 1954 addition needed to be replaced the Library Board believed a sustainable, cost effective and educational replacement was in order. HGA performed a series of roof membrane and planted roof system comparative analyses and ultimately recommended an IRMA system with a semi-intensive monothlithic planted roof. Combined with a 30 kW photovoltaic array, the 30,000 SF planted roof offers an educational experience to Library patrons from a pier-like deck, as well as live Webcam and energy production monitoring accessible via the Library’s website.

Sustainability and Design

The planted roof incorporates a series of maintenance pathways and an observation deck designed to resemble the organic veining and unfurling of a plant or leaf when seen from above. Hardy sedums that will carpet the roof in a variety of textures and colors throughout the year are accented by more extensive plantings of native grasses at the deck. These native grasses partially enclose the sweeping, curved deck as it cascades down to the roof to offer seating areas for children and adults. The deck also offers patrons unparalleled views of the County Courthouse, Marquette’s campus and the downtown skyline to the east, as well as an opportunity to view the PV array at work.

The entire vegetated roof rests on 5” of insulation installed over a hot-applied rubberized asphalt membrane directly adhered to the existing concrete deck. The IRMA system, protected from damaging UV rays by the plantings, offers the Library a 50 year roofing solution. With a capacity to divert up to 70,000 gallons of storm water runoff during a peak storm, the roof was recognized by the Milwaukee Metropolitan Sewerage District and awarded a 250,000 education grant. The Library also supplies electricity back to the grid through its solar panel array to the tune of an estimated 36,490 kWh/year. As a result it received a WE Energies Focus On Energy grant.