In a significant shift in the discussions about a proposed new home for the Atlanta Falcons, the team and the Georgia World Congress Center Authority are trying to work out a deal that would result in building a retractable-roof stadium downtown and demolishing the Georgia Dome.

The new plan comes with a higher price. A GWCC-commissioned study released Wednesday put the cost of a new retractable-roof stadium at $947.7 million, up from the $700 million estimated last year for an open-air stadium. Under either plan the public-sector contribution would be an estimated $300 million from an extension of the hotel-motel occupancy tax, passed by the Georgia Legislature in 2010, according to Frank Poe, executive director of the GWCC Authority, the state agency that operates the Dome.

Poe and Falcons president Rich McKay, who jointly revealed the new direction in negotiations Wednesday, said substantial progress has been made toward a deal but that much work remains to be done. The Falcons want a new stadium because they feel the Dome, which opened in 1992, does not offer the premium seating and other amenities that drive revenue in more recent NFL stadiums.

ProConIt: Should we demolish the Georgia Dome and replace with a new retractable-roof stadium?

Among the many issues still to be resolved: the site. In addition to a previously disclosed site one-half mile north of the Georgia Dome — a site that currently contains a GWCC parking lot and a truck-marshaling yard — Poe said another site just south of the Dome is under examination. Poe and McKay said it’s too early to know if the second site is a viable alternative.

The turn in talks toward a retractable-roof stadium means the Falcons’ original preference of an open-air facility, which would have been home to the NFL team while the Dome continued to house events that required an indoor facility, is off the table.

While an indoor/outdoor, retractable-roof facility would make the Dome unneeded, Poe acknowledged “it’s a valid concern” how the public will react to the idea of demolishing a stadium that opened just 20 years ago.

“Part of our analysis is what do we do with the footprint that the Georgia Dome currently occupies and how to repurpose that space, whether it be in the form of commercial development or some development attendant to the Congress Center,” Poe said.

The Falcons’ lease commitment to the Dome expires when the bonds that funded the building’s construction are paid off later this decade.

Beyond the hotel-motel tax, neither Poe nor McKay would provide specifics on how the proposed stadium would be paid for.

Asked if Falcons owner Arthur Blank is prepared to cover the roughly $650 million difference between the estimated hotel-motel tax contribution and the new cost estimate, McKay said only: “I think we have negotiated enough to understand what we think the financing plan would look like, and I think we would be prepared to make a deal on those terms.”

Said Poe: “Our board is certainly committed to ensure we work very hard and deliberatively to try to get a business deal that makes sense for the state and certainly understands some of the needs of the Falcons.”

For several years, the Falcons said they wanted to play outdoors in an open-air stadium. Early last year, the GWCC Authority agreed to negotiate with the Falcons toward a possible deal on an open-air stadium.

Under that scenario, the Dome would have remained open for events that require an indoor venue, such as the SEC football championship game and college basketball’s Final Four. But after many months of talks, McKay and Poe said they now agree that one stadium with a retractable roof is the correct course to pursue.

How two massive stadiums would co-exist logistically as neighbors, and how the Georgia Dome would remain financially viable over the long term without the Falcons as a tenant, proved to be thorny issues.

“What became apparent to us,” McKay said, “is to get a true long-term solution that was going to work in everybody’s interests, you were going to need to go back to a one-stadium approach.”

Said Poe: “These deals are complex in and of themselves. With two stadiums, the complexities ... get magnified by almost double.” Now, he said, “our energy is strictly focused on a single stadium.”

The GWCC Authority and the Falcons commissioned a study by Kansas City-based architecture firm Populous to examine whether a single-stadium solution might be achieved by transforming the Dome into a massively renovated, retractable-roof stadium.

The study, released Wednesday, shot down that idea.

The study said that if the Dome were expanded and rebuilt to provide the amenities sought, the new seating capacity would fall short of the minimum required for Falcons games and special events. The report noted that use of the Dome would be severely interrupted during such a project.

Also, the study contended that redeveloping the Dome with a retractable roof would cost $859.3 million, $88.4 million less than the $947.7 million cost of building new on a nearby site. Populous called that “not a compelling difference,” adding in the report: “Based on our experience in encountering unexpected conditions in existing stadium demolition and reconstruction, the cost differential ... is more likely to narrow than expand.”

The study also included projections on costs associated with the proposed new retractable-roof stadium. The big reasons for the jump in total cost, compared with last year’s estimate of $700 million for an open-air stadium: $183.6 million for a retractable roof, $8.2 million to demolish the Dome if a retractable-roof stadium is built and updating all other costs from 2011 to 2014 dollars.

“One of the concerns we had with a retractable-roof solution was cost,” McKay said. “We have come to understand that to make a deal that is in the best interests of all the stakeholders, that is the best alternative for a 30-year solution. ... We understand that ups the cost, and that principally will fall on our side of the ledger.”

If a deal is reached, the Falcons hope construction will begin in 2014 and that they will play in the new stadium in 2017.

Sonji Jacobs, spokeswoman for Atlanta Mayor Kasim Reed, said Reed supports the current proposal. It “envisions a single, multi-use, world-class stadium and event venue in the City of Atlanta,” Jacobs said in an email.

Staff writer Jeremiah McWilliams contributed to this article.