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Award Winning Green Roof Designs: The Back Story - Part 1

Posted Aug 23 2008 10:40pm

A colleague sent me a copy of the new green roof coffee table book, Award-winning Green Roof Designs by Steven W. Peck, Founder of Green Roofs for Healthy Cities . The book features the first five years of the green roofs for healthy cities national award winners.

It is the back cover that caught my eye. The roof of the first project I stamped with my seal as an architect, Oaklyn Public Library, in Evansville, Indiana, is featured there. Oaklyn was a 2004 Green Roofs for Healthy Cities Award Winner in the "intensive" (deep, complex) category.

This book brought back many memories of that unique project and I thought this would be a good time to tell that story. How do you end up with a natural mesic (wet) meadow on top of a new 18,500 square foot public library on a tight budget in a conservative city in Southwestern Indiana? I will tell that story in this Part 1 and also give some detail about how it was built in Part 2.

Evansville Vanderburgh Public Library , which serves 170,000 people, embarked on a $44 million system-wide master plan to build a new $30 million central library, two new branches and renovate three existing branches. I was a junior partner at Veazey Parrott Durkin & Shoulders at the time (an Evansville firm, now VPS Architects) and I was the designated library guy. We formed a strategic association with Engberg Anderson, a nationally-known library design firm out of Milwaukee, and won the first two projects, the new main library and the new Oaklyn Branch. Engberg Anderson took the lead on the Central Library and we took the lead on Oaklyn. A couple of years later VPDS was selected for the second round of projects as well, including another new branch and three renovations. As the associate project architect for the new main library and project architect for the other five projects, I enjoyed a very concentrated learning experience in green library design and construction. The project that will always stand out in my memory, however, is Oaklyn.

A "bargain" site was selected before the architect was on board and it was a real challenge. The seven-acre site was on a slope that dropped fifty feet from the street at the top to a swampy weed patch at the bottom. The hillside oozed water continuously. The program called for 20,000 square feet of library with room to expand and parking for 125 cars. When the design team got together on the first morning of a two-day community design charrette to map out some initial strategies to present to the public, we were at a loss for ideas. To carve out enough flat space for accessible parking and the building footprint, without creating something akin to a strip mine looked impossible. I threw out two suggestions to the team. One, it must be environmentally sustainable. Two, perhaps it could be built into the hillside as a "shining brow" for the new housing development in the Pigeon Creek valley below. So, as the community design charrettes began, we had two general concepts to present. One was a conventional green library built on the lower edge of the site and the other was an earth-sheltered library built into the hillside, with a evocative clerestory element (later dubbed the Light Bridge) visible from the street. Either would have to be built for less than the established budget of $3.2 million, including the site work.

As the neighborhood association and library staff and administration gathered for the two-day design charrette, I didn't hold out much hope for the earth-sheltered scheme. The more that scheme was discussed, however, the more it seemed to capture everyone's imagination, given the constraints of the site. Two very important questions were raised: How much more will the earth-sheltered scheme cost and how do you make sure it doesn't leak? The second question was the trickiest because library administration was well aware of water issues at a nearby earth-sheltered archabbey library and they were compiling a list of other leaky earth-sheltered libraries across the country. The first question was answered by hiring an independent cost consultant to compare the two concepts. Their study revealed the surprising answer that an earth-sheltered building would have lower initial cost, in spite of a much more expensive roof system, due to three low-cost plain concrete walls that are buried and only one that is exposed and finished. We already knew from our engineers that an earth-sheltered building would cost less to heat and cool, so having lower initial cost as well was very attractive to an organization with as long a view as a public library board. Library director Marcia Au, led an impressive board of progressive thinkers and they welcomed the idea of sustainable design, as long as it was a good long-term deal for the taxpayers.

To answer the second question, we launched into research on the state of the art in green roof design and, through investigation of Chicago City Hall's new green roof, we engaged the ultimate green roof expert, Charlie Miller of Roofscapes . Charlie had been researching German green roof technology and applying it to high-profile projects all over the United States. If you look through Peck's book, or any of the other green roof compendiums, you will see Miller's hand in many of them.

Concept site model of Oaklyn Public Library

With Charlie's help, we were able to show a number of very successful and very dry green roof projects and explain how it would be accomplished technically on this project. We were also able to provide some examples of non-leaky libraries and the most skeptical library administrator came around after visiting one of them. This exercise did not convince everyone, however. As soon as it looked like the earth-sheltered scheme would be developed, a senior partner called me into his office to suggest, in a break with firm tradition, that I stamp the drawings on Oaklyn. I gulped and said, "absolutely!"

All I had to do was to imagine every possible way that water could enter the building for the next 30 or 40 years, then we would have a good chance to keep everything dry, and I could keep practicing architecture. For months I layed awake at night "thinking like water," sometimes bolting upright to jot down notes or sketch details in the wee hours. That would continue through the construction phase, sometimes falling to sleep only to have nightmares of the whole thing gently sliding down the hillside.

One of the interesting twists came from our landscape architecture consultant, Meg Storrow, who suggested, in keeping with my directive to go green, that the site wanted to be a native mesic meadow due to the constant source of water oozing out of the hillside. Her vision was that the entire seven-acre site, less the parking, could be a self-perpetuating meadow and the site and the building could thus become one.

We were going to ask the low bid contractor to bring a wet hillside onto the roof of a public library filled with moisture-sensitive books and media to keep what the neighbors like to call weeds alive. Charlie Miller's eyes lit up at the prospect and he invented an 18-inch-deep green roof that combined a series of "ponding elements" with a back-up subterranean trickle irrigation system from Germany that looked to me very much like a cattle trough water valve you could get at Tractor Supply. To add to the complexity, he included a series of rectangular horizontal drain pipes to make sure it didn't get too wet. My thoughts frequently turned to the question of the worse case scenario. What if you had to tear all that stuff off to find a leak? Who would pay for that?

Flood testing Oaklyn Library's meadow roof membrane prior to installation of overburden.

(To be continued in Part 2)

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