The Heinz National Wildlife Refuge at Tinicum Marsh lies just around the corner from the Philadelphia International Airport. The refuge is also home to the Cusano Environmental Education Center, celebrating its first anniversary as what many consider to be the city's greenest building.

The Center's heating and cooling relies on a geothermal system. About five hundred feet below the Cusano Center, the temperature remains near 50 degrees all year round. Deep wells reach into the ground to borrow heat in the winter and cool air in the summer.

And the Center makes use of a "marsh machine," to clean and recycle wastewater. Refuge Manager Dick Nugent says the machine uses natural processes to filter water through a "constructed wetland" of PVC pipes, gravel, and marsh plants. Nugent says the city water department delivers drinking water, but the marsh machine has a more important use.

The Cusano Environmental Education Center uses a "marsh machine" to recycle water by filtering it through a constructed wetland-type area

"We wanted this here as an environmental education tool," he says. "It isn't as if we needed it for the functionality of this building. We're trying to fine-tune it. We probably don't have enough plants right now. We'll have to add more before it can be recycled back into the bathrooms. The message to take home is that the marshes serve a very important function."

Cyrus Baym is a volunteer coordinator at the Cusano Center. He says people come expecting to learn about nature, but wind up getting something special out of the building.

"The people that are coming in, they see this fabulous building, a lot of space, a lot of glass, and then when you start explaining along with the exhibits, the sustainable design features, the use of recycled materials, passive solar windows, their eyes get even bigger, they get more excited, and want to implement it in their own house."

The southern wall of the Cusano Environmental Education Center is made mostly of glass windows.

Refuge Manager Dick Nugent says there was some additional cost to innovations like the geothermal system, and the southern wall of the building which is 80-percent glass windows. But in the long run, many of those innovations will wind up saving money on electricity and heating. And the overall goal isn't to be frugal, but to teach.

On the other side of the state, another approach toward sustainable design is taking hold.

Pittsburgh is currently home to one-quarter of the nation's buildings that have been certified green by the U.S. Green Building Council. The non-profit national industry group represents design, construction, and environmental interests -- and administers the Leadership in Energy and Environmental Design, or LEED, rating system, which is used to determine the overall environmental impact of a building.

Unlike the Cusano Center in Philadelphia, many of Pittsburgh's green buildings weren't designed as educational tools. The PNC Firstside Center in Downtown Pittsburgh provides workspace for 1800 employees in the bank's technology and processing divisions.

Elmer Burger was one of the principle architects for the building. He says designing the largest LEED certified building in the country made sense for the project. The large floor space improved communication within business departments, and also allowed for extensive use of natural light.

"With a large floor plate," Burger says, "we had an opportunity to make the ceilings higher and bring daylight further into the building. So you can be as far as 125 feet away from the outside wall and still have daylight in a view.

Burger says the building's large windows give employees a view of the Monongahela River, and also save money by reducing the need for artificial light.

Rebecca Flora is director of Pittsburgh's Green Building Alliance, a non-profit group working to encourage and facilitate environmentally-friendly design in the city. She says major institutions like PNC are most receptive to the idea of building green when they can see the economic benefits.

View of the front windows of the PNC FirstSide Center from the inside.

"The myth that is out there is that green buildings cost more, and we're constantly trying to educate people that you get what you pay for. Green building adds value, and how do we equate that value with increased bottom lines is a real key issue for most people."

Flora says it's important to convince clients, not just architects of the value in green design. She says if the demand for LEED certified buildings increases, sustainable design techniques will become more common.

A number of other commercial and non-profit institutions in the city also have chosen to build green. Both the Alcoa Corporate Center, and the Greater Pittsburgh Community Food Bank are green buildings. The new David L. Lawrence Convention Center - which is still under construction, but will open the doors this month for its debut event - will be the first convention center in the country to earn LEED certification.

In fact, Pittsburgh has such a strong reputation for sustainable design, that when the American Institute of Architecture Students hosted its national conference in the city this year, the theme was "Going Beyond Green."

Carnegie Mellon Student, and Convention Organizer, Chris Reynolds says there's a tremendous interest in the subject.

"Right now, I think students are recognizing that there's a current green trend in the profession of architecture and design and construction," says Reynolds. "So students in turn recognize this is a skill and a knowledge set that they want to acquire. And I think when you say that architecture and design has the capacity to affect the sustainability and the livability of the world, that really gets students ears perked up."

Elmer Burger stands outside the PNC Firstside Center in Pittsburgh.

But Reynolds says it's important not to think of sustainable design as jut a passing trend, and there are some good reasons to think it isn't.

"It's not something that's merely aesthetic or technological," he says. "It's all-encompassing. And I think it's going to lead to better buildings. I really think that you're going to se a kind of building environment where things like LEED aren't out of the ordinary, they're code issues. Rather than being the peak, they'll become the lowest common denominator, under which you can't design. And we'll address planning of entire cities, not just buildings with these things in mind."

Today's architects are already making a difference. Elmer Burger says the success of the PNC Firstside Center has led the company to a new corporate policy. All of their new buildings will be designed to meet LEED requirements.