'Green' building windows can block cell signals

Computerworld - INDIAN WELLS, Calif. -- "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 Corp., 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 here at Mobile & Wireless Enterprise 2008, sponsored by Frost & Sullivan Inc.

The bank has its headquarters and more than 15 buildings in Charlotte, N.C. 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 multiyear 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

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.

3M Co. 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 LLC in Owings Mills, Md., 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 cellular access. 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," Bridges said.