Central Library renews environment via green roof
There are always exciting things going on in Milwaukee Public Library's Downtown Central Library, 814 W. Wisconsin Ave. But, these days, there is also some excitement on the building's roof, too.
When the library needed to replace its 25-year-old roof last year, instead of going for a conventional roof, a 30,000-square foot green roof was constructed and 132 solar electric panels were added to generate about 36,000 kilowatt hours of electricity per year. That's enough to power four homes annually.
"Everyone's very enthused about it," says the library's public services manager Christine Arkenberg, on a recent visit that begins on the library's first floor, where there is an area dedicated to the green roof initiative.
There, visitors can see books about green issues, view explanatory materials, see a monitor with status updates on how much electricity is being generated, watch a video screen slide show and pick up brochures.
You can also meet a tour guide in the rotunda to take a trip up to the green roof. Free tours are offered at 1:30 p.m. on Mondays, Wednesdays and Saturdays. Nine librarians, including Arkenberg, are trained as "Roof Rangers" and take turns leading the tours.
The tours began last July and started up again this April 16.
"There is an educational mission," says Arkenberg as we wander the rooftop deck, which offers views not only of the roof but out to the city skyline to the east, to the former Pabst Brewery and the County Courthouse to the north and out to the west as far as the eye can see.
"It is meant to illustrate the principal of green roofs. Even if you can't do this (kind of roof) at home, if you have an area where you see rainwater is just flushing off your yard, maybe put in a rain garden," she says.
"Also, replace lawn with rain gardens with native plants to absorb the water to slow down the runoff. Disconnect your downspouts and (do) anything you can do around your house to de-concretize your area."
The new roof – designed by architectural firm Hammel, Green & Abrahamson and built by F.J.A. Christiansen Roofing Co. – cost quite a bit more than a conventional replacement would have.
The latter was estimated at $700,000 and the former ran about about double. Just under a million dollars came from the city's capital budget and the rest arrived in the form of grants from We Energies, Focus on Energy, the Milwaukee Metropolitan Sewerage District and the Milwaukee Energy Challenge Fund for Solar Electric System.
The green roof is expected to have at least double the life span of a conventional roof, though some experts have suggested it could last much longer than that, says Arkenberg.
The green roof is a bit weightier, she says, but that's not an issue because the library annex below was built with an eye toward adding a fourth floor that was never constructed.
At the moment, the roof doesn't really look very green. There are patchy green spots, where some of the eight varieties of sedum, chives and Karl Foerster reed grass are taking hold.
"Our roof won't really look green until probably the end of its third year," says Arkenberg, after explaining that instead of seeding, the plants were introduced to the roof environment by broadcasting seedlings.
"But the plants that were selected are all very drought and water tolerant," she adds. "The growing medium is all inorganic material – lava rocks and things like that. It is able to support the roof growth. The decay of the plants as they die off will provide fertilizer. Maintenance is quite minimal."
Back before we stepped out into the sun-drenched roof Arkenberg showed me a model of the structure of a green roof.
"Ours is a little different because we have two layers of insulation," she said, as we looked at the model. "The green roof structure's bottom layers are waterproof, because it has to protect what's underneath. After that it's pretty much insulation – either by foam or with air – something to prevent the penetration of the roots, and there's some water storage capacity in here and also filters to help filter out some of the impurities in the water.
"All of this is made from as much recyclable material as it can be."
When we stepped out onto the deck, she noted that it, too, was constructed from recycled plastic material.
Looking north off the deck, you see the 132 solar panels. The energy is not stored at the library but rather passes through a meter and out to the power grid. But that is not the roof's only positive energy impact, says Arkenberg.
"It's about 1-2 percent of our energy consumption," she notes, "about enough so far to operate four homes for a year. It's a dent. But also we will be consuming less because of the roof's insulating properties."
Because the roof doesn't get as hot as conventional roofs, it also reduces the library's contribution to the urban heat island effect.
"That means that all of these rooftops," says Arkenberg, sweeping her arm off toward the buildings out to the west, "when it's a hot day, they can get to be 120 degrees for a white roof, and a black top can be 160 to 180 degrees and all that heat is reflected back up into the atmosphere."
The library's green roof, she estimates, would reach about 85 degrees on an 80-degree day.
"The plants absorb solar energy," says Arkenberg, "so it will be better when the roof is 'greener.' When there are more plants, it will also improve the oxygen in the air."
And the roof is a big improvement in terms of runoff, too, of course.
It can absorb 50 to 90 percent of rainfall and when there is runoff, Arkenberg says, it is delayed, giving storm sewers a chance to catch up.And because the roof filters out impurities, any water that ends up in the sewer is cleaner. There are a few overflow drains to prevent standing water.
You can learn more about the roof and the tours at the Milwaukee Public Library Web site, where there is also a green roof webcam. But there's nothing quite like experiencing the view for yourself. Arkenberg will be happy to show you around, especially on a nice day.
"On a beautiful day like today, who can argue," she laughs.
Juan | May 18, 2011 at 12:03 p.m. (report)
While I support the library's green roof project, one has to wonder about their personnel assignments. Assuming that the information published in the City of Milwaukee's Visual Organization Inventory is correct, the librarian mentioned in the article has a salary between $60K and $80K/year. On the one hand, library hours are being slashed because of budget cuts. On the other hand, they can apparently afford pay a librarian approximately $35/hour to function as a tour guide. According to various websites, the average salary for tour guide should be in the $20/hr range. One would think they could have a lesser-paid staff member give these tours, when required.
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