As many as 30,000 green-building advocates from around the world will convene in Philadelphia for an industry conference three years from now.

And already, the worrying has begun about the spotlight this high-profile, November 2012 event - sponsored by the U.S. Green Building Council, a driving force in the sustainable-construction movement - will focus on this region.

"If you invite 30,000 sustainability/green-building advocates to your city, you better hope you have some good news for them," said Heather Shayne Blakeslee, programs and advocacy director at the Delaware Valley Green Building Council, the national group's only Pennsylvania chapter.

Even the most enthusiastic supporters acknowledge that getting to the point where building green is more the norm than the exception will be a rigorous road.

They cite the need to change state and local building codes and policies to specifically require green amenities, and convert skeptics who doubt such construction is worth the investment.

This week, the push begins to help ensure that Philadelphia will have an impressive array of sustainable construction to show off in 2012.

About 300 officials from government, higher education, commerce, and nonprofit organizations, including Gov. Rendell and Mayor Nutter, will meet tomorrow and Thursday at the Sheraton City Center Hotel "with the goal of fostering unique partnerships for research, investment, collaboration, and education" in green building, said Rob Fleming, director of Philadelphia University's graduate program in sustainable design.

"This event seeks to establish a new kind of conference - a forum for ideas, policy, and strategies that will underpin the green economy for decades to come," said Fleming, one of its organizers.

The BuildGreen 09 Conference is being held by the Delaware Valley Green Building Council, which will make news of its own there.

The conference's first day also will be the first day on the job for the building council's new executive director, Janet Milkman, who has led the smart-growth advocacy group 10,000 Friends of Pennsylvania and, most recently, Erthnxt, a program to connect children with nature.

In an interview last week, Milkman summed up her new challenge this way: "Our job is to make the case" for green building.

It is a case that has to have consumers in mind - home buyers, and commercial property owners, and tenants alike, said Kevin Gillen, vice president at Econsult Corp., a Philadelphia economic-analysis firm.

"I'm not in favor of green if it means expensive additions that make housing unaffordable," Gillen said.

With its sea of rowhouse roofs, Philadelphia could be a prime candidate for solar panels. But with photovoltaic systems costing at least $35,000 even with state rebates, most homeowners cannot afford to go solar, he said.

Because the city already ranks among the highest in the nation when it comes to average construction costs, Gillen said that driving those costs even higher in the name of sustainability was the last thing Philadelphia should want if it hoped to encourage more economic development.

If city government is not going to help drive down those costs by instituting new zoning and building-permit processes that would make it easier - and cheaper - to incorporate green features into new construction and building retrofits, then it should consider tax breaks and public subsidies for projects that do, Gillen said.

City Council had hearings in the spring on a proposal to extend the 10-year tax abatement to buildings qualifying for platinum certification under the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) rating system. Work on that is continuing.

Sam Sherman, president of the 150-member Building Industry Association, said the discussion about what constitutes green needed to look beyond LEED.

"How green can it possibly be when every employee is driving 30 or 40 miles to arrive at a LEED-certified office building?" he asked.

At the townhouses he has built recently in the city, Sherman has not sought LEED status, but he has added extra insulation and installed high-efficiency water heaters to reduce operating costs.

The green movement, he said, is "too focused on technology [when] it needs to be focused on common-sense planning and taking advantage of existing infrastructure."

Cities such as Philadelphia, Sherman said, are already sustainable because they are walkable and oriented to public transit. One way it could get greener is to grow the job base so more people could walk to work, he added.

In the suburbs, where the green movement for decades meant protecting open space, it is increasingly gaining a construction connotation.

Last Wednesday, night, the Lower Makefield Township supervisors took a step toward adopting an ordinance that would require all new municipal construction or major renovations to be built to the LEED silver standard. They voted to advertise the proposed ordinance, which will be subject to public comment before a final vote.

As a member of the township's environmental advisory committee, Lisa Grayson Zygmunt promoted the ordinance as a first step toward green-building measures with broader applications.

"We felt it was important the township walk the talk," she said, "before it would ask the private sector to do the same."

Contact staff writer Diane Mastrull at 215-854-2466 or dmastrull@phillynews.com.