A Clear Day in D.C.

Technology also has made the current generation of glass buildings distinct. Manufacturers sell more energy-efficient glass, which contains coatings that block harmful rays.

But the quest for sustainability may still be a lofty goal. Shalom Baranes, a District-based architect, said transparent buildings in Europe are more energy efficient because builders use more layers of glass.

Developers in Washington, he said, are more reluctant to use multiple layers because they eat into the leasable space.

"We architects love to design glass buildings, and we talk about the positive aspects," he said. "The negative is that they are less energy efficient than stone buildings."

Even owners of existing buildings are switching to glass, hoping that modernization will induce higher rents. At 1225 Connecticut Ave. NW, a facelift is turning a 1960s-style concrete facade transparent.

The renovation is among 12 glass projects in the region being overseen by James G. Davis Construction, eight of them within the District. Glass is not in vogue in the suburbs, said Dennis Cotter, a company executive, because office rents are not high enough to support the cost of the material.

And although developers are enlarging living-room windows in Washington apartments, cost concerns are keeping them from constructing the fishbowl-style condos now popular in New York.

For architects who have devoted their careers to creating buildings that blend in with monumental Washington, the glass craze can be a bit bewildering.

Graham Davidson, whose firm has designed and restored downtown buildings, said he's fortunate that the bulk of his work is not rooted in Washington.

"We'd be dead," Davidson said. But he added that he knows nothing is forever, especially when it comes to style. "It's just a fad," he said of the yen for glass architecture. "It'll go away."