Office space in city rebounds

With the vacancy rate for top-grade office space estimated between 10.5 percent and 12.5 percent by commercial real estate firms, rumors have circulated of plans for other new high-rise offices.

The vacancy rates vary by firm because of different methods for calculating the rate and the different classification of top-grade space.

Comcast has an option to lease a 20-story building that would be built by Liberty on the same site as the new building. "We are looking at a variety of scenarios for Phase Two," Gattuso said.

Another possible new-building site, say real estate experts, is near the sleekly modern Cira Centre in West Philadelphia. The Cira Centre, which opened in 2005, is almost fully leased, according to commercial real estate firms.

Campoli, vice president for this region of HRPT Properties Trust, of Newtown, Mass., was one of the loudest critics of granting subsidies to Comcast Center. "There's far more important things for the state to spend money on," he said yesterday.

HRPT Properties owns the Centre Square building, which is used by Comcast now, as well as Mellon Bank Center and other high-profile Center City buildings. Campoli said about 70 percent of the space that Comcast would leave when it relocates was leased. "We're bullish," he said of the downtown office market, "we're pushing rates. It's a surprising turnaround."

View a slide show of yesterday's topping-off ceremony for the 57-story Comcast Center at