McBee's enthusiasm, if unsettling to coworkers, is understandable. This isn't just a garden. It's a "vegetated roof," the first in Center City, largest in Philadelphia, and part of a $12.5-million renovation to free the Friends Center at 15th and Cherry Streets from reliance on fossil fuels.
Once the sedum spreads into a verdant cover atop the center's roof, McBee says, it will help insulate the three-story building below, end the center's contribution to the Center City "heat island" radiating into the atmosphere, eliminate about 90 percent of the building's rain runoff, and triple the 25-year life of the new roof - modern energy-saving insulation with a vinyl cover like a pool-liner - under the four inches of soil.
Because sedum does not grow taller than six inches, no mowing is involved, although Muller said someone would be hired to weed the roof once or twice a year.
There is also a 10-kilowatt array of photovoltaic cells - solar panels - that last month began generating 2 percent of the center's electricity.
Still to come: up to six 1,500-foot-deep geothermal wells under the 15th Street sidewalk that will use groundwater and a heat exchanger to reduce by almost 40 percent the energy needed to heat and cool the building, and holding tanks to reuse rain runoff from the center's adjacent 1856 meetinghouse for toilet flushing.
High-tech may not be the first adjective most people associate with Quakers.
But, McBee explained, as plans to renovate the Friends' 34-year-old office building evolved, "greening" the structure came to be seen as the only way to be true to Quaker principles of peace, simplicity and social equality.
"This is the 21st century," said McBee, director of the Friends Center's capital campaign. "There are wars and illness and disease and global warming that are consequences of our behavior."
Moreover, McBee said, as Quakers they could not expect others to change their environmental conduct unless the Friends did so themselves. "We want to be a model for other property owners and building professionals to come here, kick the tires, learn that these things work, that they're cost-effective, they're beautiful, there's nothing you're really sacrificing and it's worth doing," she said.
Veteran architect Mark Ueland, a founding partner of the Center City firm of UJMN Architects + Designers, the designer and overseer of the Friends Center project, called it "by far the most challenging, ambitious project I've dealt with in more than 40 years. It's quite remarkable."
While many builders today make use of green, energy-saving technology, Ueland said it was rare to do a comprehensive green renovation of an existing building.
When complete, he said, the Friends Center would be a model of sustainability for the city.
No one questioned that the Friends Center's offices needed a rehab. The original tar-paper roof needed to go, there was no insulation in the walls, and windows did little to keep heat out during summer or in during winter.
Three years ago, as project planning began, some Friends Center board members began urging a "green building."
The Friends Center applied for and received a $75,000 planning grant from the Kresge Foundation, which encourages green building design.
The study and the discussions it triggered were "transforming," McBee said.
"We talk about how big a car you drive and that a Hummer might be a profligate waste of energy, but what about a huge new home?" she said. "We haven't come to see how important . . . changing the way we think about our buildings is to making a significant impact on climate change and energy use."
The Friends Center's financial advisers were skeptical. They wanted a 20-year cost-benefit analysis comparing a conventional renovation - about $8.5 million - with the $12.5 million green makeover.
The results: $50 million to run the building over 20 years with a conventional rehab, $45 million if the Quakers went green.
"So the bottom line to our careful money folks is we're going to spend $50 million one way or the other," McBee said. "What we have is the choice of what we're going to spend it on. We can spend it on making our building right, being responsive to the needs of the 21st century, living up to the principles for which Quakers are known . . . or we can just do business as usual because everything else looks too complicated and costs a little bit more up front."
Ueland and his firm jumped at the opportunity to, as McBee said, "turn Quaker gray into Quaker green."
Not everyone was convinced. The Friends' engineering firm's reaction was, "That's impossible, you can't do that." McBee said the firm was replaced.
Muller himself was skeptical, McBee said, asserting: "It's weird, expensive, and we don't need to do it."
Now you can almost see Muller's mind figuring the savings.
The holding tanks to capture rain runoff for toilet flushing "will eliminate almost all of our potable water bill," he said.
The energy savings from the 10-kilowatt solar array will be supplemented by revenue the Friends Center can earn through solar credits by selling power back to utilities such as Peco Energy Co. under a federal solar-incentive program.
"I'd love to get those 100 kilowatts up on the roof there," Muller said, referring to the ability to expand the solar array. "Twenty percent of your energy you're generating yourself, plus $40,000 a year or more in credits. That's great."
To hear an interview with Friends Center representatives discussing their "green" building, go to http://go.philly.
Contact staff writer Joseph A. Slobodzian at 215-854-2985 or email@example.com.