Buildings wear green on top -
Check out the benefits of buildings topped with "green roofs"
A fine meadow of native prairie grasses and wild flowers sprouted when the new Oaklyn Branch of the Evansville Vanderburgh Public Library opened in 2003. But the plot of green didn't require more land. Just a better plan.
The plants grow across the library's flat 17,250-square-foot roof. Underneath 16 inches of soil, the library stays inherently cooler in summer and warmer in winter. And the roof provides the ecological benefits that plants bring.
"We wanted to accommodate the marriage of function and aesthetics," said Marcia Au, director of the public library system. The building offers both, topped off in an environmentally friendly way.
The building has received national attention and won multiple design awards. But the local library patrons who are flocking to the new branch are the true beneficiaries. Book circulation has increased three-fold at the branch since moving to the new building in one of the fastest growing areas of Vanderburgh County.
The new branch sits in a park-like setting near a creek and woods. The location sloped steeply so the single-story building's green roofscape was designed to blend into the uphill side. The green roof combines with three super-insulated subterranean walls to enhance the building's energy efficiency. Though the new branch is three times larger than the building it replaced, utility costs are comparable.
Oaklyn's green roof is one of hundreds that have been planted in mid-sized and major cities around the country in recent years.
Green roofs, also known as vegetated roof-tops or eco-roofs, are essentially rooftop areas that have been installed with living vegetation, from small gardens and planters to roofs that are completely covered by sod and plants. They have roots in ancient cultures but are viewed as a wave of the future. Green roofs offer a variety of advantages that include:
- helping regulate the temperature of the building beneath;
- improving air quality by removal of carbon dioxide and absorption of pollutants;
- providing a valuable wildlife habitat;
- regulating water flow from the roof by slowing the flow rates;
- requiring little maintenance;
- reducing outside noise through the roof;
- reducing the "urban heat island effect."
From the fabled hanging gardens of Babylon to the sod homes of Viking, humans have been growing plants on roofs since ancient times. The modern green roof has been cultivated in Europe for decades. The industry is just a few years old in the United States.
Green roofs are being touted as the answer to a number of environmental problems. In cities, the roofs are a way to recreate the Earth's natural footprint that has been displaced by buildings. Experts believe the roofs can reduce even the lethal effects of heat waves, such as the one that led to the deaths of 465 people in Chicago in 1995.
Chicago has become a leader in green roofs with over 2.7 million square feet under green roof, including City Hall. Because Chicago shares City Hall with Cook County, only the city side of the building has been green roofed. On days when ground temperatures reached 95 degrees, the reading on the City Hall side of the roof was 91 degrees. On the county's half, which was covered with black tar, the temperature was 169 degrees. The city saves $40,000 a year in air conditioning costs from this one green roof alone.
You may not be able to tell books by their covers. But buildings covered in green, like Evansville's Oaklyn Branch, tell volumes about the love of form and function, and the environmental concerns and forward thinking of the people and organizations within.