Juneau getting its first green roof

Posted: Sunday, August 01, 2010

Construction of the new Downtown Transportation Center at the corner of Egan Drive and Main Street has included a new feature, something to provide some green in more than one sense.

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Michael Penn / Juneau Empire
Michael Penn / Juneau Empire

The project's new transit center will be home to a "green roof," which the minds behind it say will be the first of its kind in Southeast Alaska. In their simplest form, green roofs are those that contain living plants as part of the roofing structure.

Landscape architect Christopher Mertl explained the thought behind creating this visual aid made it quite a detailed project.

"We wanted to create something that's going to be attractive and environmentally sensitive," Mertl said.

Around 1,000 square feet of the transit center's roof are covered with trays of sedums and native Alaskan sea thrift. Mertl said he chose these species not only for their aesthetic appeal, but for their low-maintenance benefits. He said these plants could survive heavy rains, droughts and heat conditions without requiring caretaking. Once planted, they would be relatively independent and save in maintenance costs.

Juneau city and borough project manager Skye Stekoll said the low-maintenance aspect was an important one for the city.

Stekoll is overseeing the whole downtown project. He said the city is fully behind the idea of a green roof.

"We pick and choose what elements go into a project, and we figured this will be something that everyone around here will appreciate," he said.

Mertl said there were a few specific reasons he wanted to build such a roof in Juneau. The first was for its aesthetic value.

Mertl wanted the sight of the plants to include artistic and cultural value and so designed each side of the roof after Tlingit patterns found in basketry that would tell stories appropriate to their Juneau setting. He said the square trays were perfect for forming such patterns.

The side composed of red and yellow sedums represents water and tides, which Mertl said is perfect because of the proximity to the Gastineau Channel shoreline.

The other side with red sedums and sea thrift stands for "shaman" or "chief." Mertl explained this idea came from beliefs that this area was a boundary marker to Indian tribes.

Because the roof is not accessible to patrons, the sight of it must be taken in from above. It can be viewed from the decks of the neighboring four-level parking garage and from the site of an adjacent park project known as "Telephone Hill Park."

Mertl added the flowers bloom at different times, making the designs appear different at different times of the year.

He added future sidewalk paving projects in the area would involve similar patterns.

The second reason for the project is for long-term cost savings. Mertl said the greenery acts as insulation, which can save on heating and cooling costs.

Other practical applications are slowing storm water runoff by absorbing moisture, and protecting the water membrane on the roof, prolonging the roof's longevity. He said regular roofs can typically last 30-40 years, so time will tell how vegetation affects it here.

He said all of this combined with the plants' low maintenance will save the city money.

Green roofs can act as a habitat for bees and may help cool the environment.

"We don't need to mandate it (green roof construction), but environmentally it's the right thing to do," he said.

Green roofs are not a new concept. While their history goes back centuries, Mertl said modern ones have become popular fixtures in larger cities. Even some buildings in Anchorage and Fairbanks have them.

"It's the first in Southeast Alaska, so we wanted to show it can work here," Stekoll said.

Mertl said he has had this roof in mind since planning for the downtown renovations began two years ago.

Along with the design and working with the city to implement the idea, he conducted research to determine the practicality of the species he wanted to use. Part of this research included leaving plants unattended since last September to make sure they would survive all types of weather on their own.

"We did a fair good bit of research," Mertl said.

Mertl worked with the architecture company Jensen Yorba Lott, which designed the roof from the beginning. He has since formed his own company, Corvus Design, and is continuing his work on this project.

Once completed, the transit center beneath the roof will house a waiting area for the bus line, complete with concessions and restrooms. A police substation and break room for the bus drivers will also be there.

• Contact Jonathan Grass at 523-2276.

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