"It's not easy being green," said Kermit the Frog.

And Eileen Bridges would agree.

Bridges, a senior vice president for strategic planning and technical architecture at Bank of America, said the bank has discovered that energy-efficient windows in its newer buildings are blocking cellular phone signals.

As a result, the bank faces paying premium access charges to wireless carriers to enhance indoor cellular signals, Bridges said. She spoke yesterday at a panel discussion on wireless technology at Mobile & Wireless Enterprise 2008.

With more than 15 buildings in the city where the bank is headquartered, the three buildings designated as green are the ones where the cellular signal problem has been detected, Bridges said.

Bank of America is making good progress on a multi-year deployment of voice-over-IP phones for nearly all of its 200,000 workers, but the cellular problem in the green buildings wasn't anticipated, she said. And Bridges' staff isn't yet sure how widespread the problem might be, though she says she suspects "we're at the tip of the iceberg."

Metal in the mix

Several analysts and IT managers at the conference said they had never heard of the problem before, but Bridges said the interference has been linked to a special doping material used in the manufacturing process.

Metal is a well-known enemy of cellular signals, and companies in some large steel-framed buildings know that they need to enhance signals -- especially in the deep interiors of such buildings. An entire industry has developed around Fixed Mobile Convergence to allow companies to link wireless phones to wired network architectures, sometimes by using phones that operate on both Wi-Fi and cellular networks.

But metal in window materials is a more recent development. In recent years, some green-building architects have relied on new windows that have a thin metallic coating that reduces energy usage by reflecting heat into the building in the winter and out in the summer.

US company 3Com announced a Prestige series of glass in 2006 that eliminates the metal, partly to reduce corrosion and partly to reduce the cellular interference.

On the flip side, some businesses have used the transparent metal linings in some window glass as a security advantage, blocking Wi-Fi piggybacking from outside -- not to mention hackers sitting in a parking lot hoping to read data moving inside the building. Astic Signals Defenses sells such glass specifically for that purpose.

Bridges said having wireless carriers add in-building equipment to boost cellular signals for Bank of America has been complicated. Sometimes the booster equipment will reach only to certain floors of a building, leaving some end users without access to cellular. That, in turn, has led to employees wondering why they weren't favored by the IT shop to get acceptable cellular signals, she added. "It's involved," she said.