City says green roofs at O'Hare well worth the effort

Spring - and the best time of the year for many gardeners.

Lilacs, forsythia and tulips grace suburban yards and parks. And on the roof of the south airfield lighting control vault at O'Hare - the sedum's just getting started.

When you think of O'Hare International Airport, images of runways, terminals, and parking lots spring to mind. But the city of Chicago actually operates five green roof projects and is planning six more.

"We believe going green reduces our dependency on other sources of energy, making Chicago's airports good neighbors to the surrounding communities," Chicago Department of Aviation Commissioner Rosemarie S. Andolino said.

O'Hare has about 33,967 square feet of green roofs and anticipates growing that to 390,840 square feet in the future.

What does the city plant on its green roofs? Varieties of sedum, a flowering plant that tolerates drought and doesn't attract wildlife. The sedums used by the city have white or yellow flowers and are hardy ground covers.

The concept works to save energy in several ways. Green roofs absorb heat in the summer and cold in the winter, reducing heating and cooling bills and energy use. They also prolong the life of the average roof from 20 years to 50 years.

There's other benefits too. Vegetation can absorb dust and filter airborne particles. The plants and soil also help capture sound waves, aviation department officials said.

In addition, green roofs counteract the urban heat island effect generated by large amounts of paved surface, typically found at airports, Andolino said.

It's possible to glimpse some of O'Hare's green roofs while traveling between the terminals and remote parking on the airport's light-rail trains.

Right now, they're atop two north air traffic control tower buildings, a lighting control vault in the south end of O'Hare, a guard post and a rescue and firefighting facility.

A FedEx cargo building currently under construction at O'Hare will feature close to 200,000 square feet of green roof coverage, which will make it one of the largest green roof areas in the United States, Andolino said.

The vegetated roofs at O'Hare and Midway International Airport demonstrate that "going green at airports is possible and cost-effective," Andolino said.

While green roofs at airports are more common in Europe than in the United States, "airports nationwide have recognized that green alternatives do exist and more are being created every day."