Trees are the hallmark of the Arbor Day Foundation.

But times change.

And the Nebraska-based foundation is changing, too, by expanding its mission of inspiring people to plant, nurture and celebrate trees.

On Tuesday, workers will begin installing a "green roof" on the foundation's administrative building at 12th and P streets in Lincoln.

If you're thinking a very big lawn, you're not too far off. Green roofs are sprouting all over the U.S. as an eco-friendly way to reduce energy costs, control runoff and help clean the air.

The Arbor Day Foundation's green roof will cover 7,369 square feet and will include a 400-square-foot test plot for University of Nebraska-Lincoln professor Richard Sutton, who is trying to find out which species of prairie plants do well on urban rooftops.

"It's a great opportunity for us to make others aware of what's possible even on an existing structure," said foundation president Matt Harris. "As environmental stewards, we're trying to walk the walk."

The idea for installing a green roof on the building and using it as a demonstration project grew when the foundation decided to renovate the building, which houses the foundation's administrative offices and membership services. Most people are more familiar with the organization's other facilities - Lied Lodge and Conference Center and Arbor Day Farm - in Nebraska City.

"It fits with their mission of pushing the envelope on the environment and making people tune into it," Sutton said.

The foundation faced a challenge because the existing roof couldn't support a lot of soil. Working with Sinclair Hille Architects and Scott Enterprises Inc. in Omaha, they came up with a lightweight design that uses only 2.5 inches of a special formulated growth medium. The roof also will be planted with sedum and other low-growing shrubs and grasses to minimize weight.

Sedum, which is similar to a succulent, is an ideal plant for a green roof because it lies on the surface, does well in drought conditions and can withstand intense temperatures, Sutton said. Some roofs can reach more than 150 degrees in the summer heat.

The soil medium, made up of shale, clay and compost, provides nutrients for plant growth, while also absorbing water for later release, Sutton said.

Green roof technology started in Europe and has gradually made inroads onto new and existing buildings in the United States. Sutton said they protect the existing roof membrane from harmful ultraviolet rays, thus extending the life of a roof by 10 to 20 years.

In addition, green roofs lower the heating and cooling costs of a building, he said.

But there is a rub. The upfront costs for installing a green roof are much higher than a typical flat roof.

"Typically, green roofs cost somewhere between 35 to 50 percent more than simply replacing a liner," Harris said. "The payback is in additional life and heating and cooling savings."

He estimated that the green roof will reduce the foundation building's heating costs by 20 to 25 percent annually.

Harris declined to say how much the foundation is spending on its green roof. He said financial support has come from its membership and the WRK Family Foundation in Lincoln. The Arbor Day Foundation lists over one million members, mostly in the United States.

People who are interested in green roof technology and want to see it up close can call the foundation and make an appointment after it is installed. Planting will start in September and it may take a year or two for the green roof to be lush.

Customers of the new Qdoba Mexican Grill, which is being built next to Panera Bread, will get a close-up view of the green roof.

Sutton said the restaurant plans to put a deck on the roof for dining. An informational display will be nearby to explain the concept of green roofs.

Diners will also get a view of Sutton's 400-square-foot test plot.

"I'm pushing the idea of using our prairie plants, particularly prairie plants from western Nebraska where we have good survival," he said.

Eventually, Sutton would like to see green roofs on existing public buildings and big box commercial stores such as Walmart. He said the green roof technology being used for the Arbor Day Foundation building would be ideal because it fits roofs without a great deal of support.

Sutton noted that Penn State University has mandated green roofs for any new buildings on its main campus. Unfortunately, he said, there are no green roofs on the UNL campus.

"Maybe we should be in the forefront," he said.

Reach Algis J. Laukaitis at 402-473-7243 or