While fewer than 5,000 people came to the first Greenbuild conference, in 2002 in Austin, Texas, this week's conference in Philadelphia attracted more than 30,000 - evidence that green building is booming, officials said, even as the building industry has been flat in recent years.
Indeed, green building has enough heft to attract former Secretary of State Hillary Rodham Clinton as the keynote speaker Thursday night.
"The way forward is the sustainable way," Clinton told the green builders, who packed the Liacouras Center. "The work you are doing is needed by the whole nation and the whole world."
The former first lady - who smiled when an audience member shouted "Hillary in 2016" during a question-and-answer session - emphasized the role sustainability could play in propelling the country's economy and ensuring domestic energy security.
At more than 100 presentations during the week, speakers told architects, building owners, code officials, contractors, designers, and home builders about the latest techniques - and how to use them to make better buildings.
All this matters, experts say. Our built environment - homes, office buildings, hospitals, schools, and other structures - accounts for 40 percent of energy use.
Lately, said council senior vice president Kimberly Lewis, the talk has extended beyond the performance of a building to how it could affect the health of the people inside it.
The show began - almost literally - on Sunday at the Eagles game, where the team was awarded LEED certification for its solar- and wind-powered Lincoln Financial Field.
LEED is a green-building rating system devised by the council. It is highly sought-after by those who want to verify that they are as green they think.
But so many buildings are achieving LEED status that at the show, the council rolled out a new version, expanding it to more kinds of buildings - now even a warehouse can become LEED-certified - and adding "impact" categories such as climate change and human health.
What Heather Blakeslee liked about the show was the chance to show off the region's sustainability.
Blakeslee, deputy executive director of the Delaware Valley Green Building Council, said it was little known that there is so much green building in the region.
When passing the old post office across from 30th Street Station, recently renovated into office space, she said, she thinks about how "amazing it is to know that it is a historic building, but on the inside, it's state of the art."
"It's a little like living in The Matrix. Once you know the code, you can see how amazing all the work is that's happening," she said.
One group launched a green-schools initiative. Another, a consortium of seven companies working for the nonprofit Urban Infrastructure Initiative, gave Mayor Nutter a 48-page report detailing steps the city could take on its path - if Nutter has his way - to becoming the greenest city in the nation.
On the exhibit floor, companies touted the latest in nontoxic pipes, smart thermostats, efficient lights, insulating windows, and porous paving.
Philadelphia-based Revolution Recovery's booth was made of materials scrounged from the region.
In the end, Greenbuild took its message down to the very trash it generated.
As part of an attempt to divert 95 percent of the waste from landfills, the conference area was dotted with small stations where three bins stood side by side - for compostables, recyclables, and the landfill.
Inquirer staff writer Alison Burdo contributed to this article.