Milwaukee’s Main Library Greens Up the Rust Belt

Take a grand old city library with a domed exterior and palatial marble rotunda inside. In the mid-1950’s, expand the landmark with an addition behind the 1898 building. Then, in 2010, top off the addition’s sturdy roof deck with the icing on the cake: a 33,000-square-foot green roof plus an array of 132 solar panels. Result: a big bang for your energy-savings buck.

The Central Library is one of Milwaukee’s showcase buildings for green infrastructure. Its green roof is an inverted roof membrane assembly (IRMA) built to withstand hailstorms and other punishing weather. It has ten layers, each with its own function, from insulation, to moisture retention, to filtration. The roof’s crowning layer is a low-maintenance perennial garden planted with 12 varieties of sedum (succulents) plus chives and reed grass. This durable but lightweight mix of vegetation, soil, membrane, and other media keeps the structure below from overheating in summer and getting too cold in winter.

The roof can soak up as much as 70,000 gallons of rain, slowing down the flow of water and preventing it from flooding city sewers. It becomes a mini-ecosystem that is attractive to birds: every year a family of mallards settles there, to the delight of library staff.

Thanks to a 2019 upgrade, the original number of solar panels was almost quadrupled by installing 391 more rooftop panels on the tallest portion of the addition. All told, both solar arrays together can generate about 190,000 kilowatt hours (KWh) per year of power. Of this amount, whatever electricity the library doesn’t use shoots out to the grid, earning the library a sizeable credit on its electric bill. Replacing bulbs with LED lights and upgrading the HVAC system with Energy Star equipment have also cut down on inefficiency.

The library offers seasonal roof tours. So cuddle up in the Reading Room with your favorite book, and then head on up to the green roof to see it for yourself. You’ll get a 360-degree view of Brew City as well.