A large part of Fallingwater's appeal is its transparency, the way the windows allow the interior to seem to merge with the landscape. So when Fallingwater's windows begin to fail and fog, that's a problem.

The house museum's owner, the Western Pennsylvania Conservancy, replaced the original, 50-year-old quarter-inch PPG plate glass windows in the late 1980s with laminate glass, which sandwiches UV-filtering glass between PPG plate glass. The UV filter helps prevent sun damage to art and furnishings at Fallingwater, the Fayette County woodland home Frank Lloyd Wright designed in the 1930s for the Edgar Kaufmann family.

"The humidity and moisture attacked the edges of the laminate glass and caused it to delaminate from the inner layer and to cloud," said Fallingwater curator Justin Gunther.

The laminate is failing both at the base of some windows and at the edges of windows where glass meets glass in mitered corners.

The windows will be replaced with a new laminate glass, which sandwiches a Dupont's Sentry Glas between PPG's low-iron Starphire glass.

"The technology has improved over the last 20 years," Gunther said. "It's been tested for about 10 years, and it won't delaminate that way."

There are about 320 windows in the main house and guest house that will need to be replaced over the next five years, and to help cover the cost, the conservancy has launched its Window Legacy Fund. It hopes to raise $500,000 not only to cover the cost of replacement glass but also to sock half of that amount away for window maintenance.

"Because the glass will fail again," Gunther said. "We've kind of resigned ourselves to that fact. Twenty-five or 30 years down the road, the funds will be in place and hopefully technology will have improved even more."

The conservancy already has raised $135,000 toward its goal. Donors are being asked to underwrite specific windows, beginning at $500, and will be recognized in the Visitors Center, perhaps with their names etched on a donor window there.

"Donors' names will forever be associated with [the window they endow]," Gunther said, "even when the glass is changed again."

Glass replacement begins next month in the living room, with all of the window and door glass that opens to the East Terrace.

To learn more about the Window Legacy Fund, visit a new section of the Fallingwater Web site (fallingwater.org/113), which enables visitors to browse all windows available for endowment within specific giving levels and make their selections. Interested donors also may contact the conservancy's development office at 1-866-564-6972 or development@paconserve.org.

The Community Design Center of Pittsburgh's Design Excellence Lecture Series begins on Nov. 23 with a talk by Terry Schwarz, senior planner with the Cleveland Urban Design Collaborative at Kent State University.

Alan Greenberger, executive director of the Philadelphia City Planning Commission and acting deputy mayor for planning and economic development, speaks on Feb. 22, and Robert Freedman, Toronto's director of urban design, on April 10.

Themes include city-building, visionary planning, sustainability, community engagement and civic awareness. The series is held at the GRW Auditorium at Point Park University, 414 Wood St. Each event starts at 6 p.m. and includes a 30-minute lecture by the featured speaker, a 30-minute panel discussion by local design practitioners about the evening's presentation, and a reception.

Tickets to individual lectures are $20; a series subscription is $45. Information: cdcp.org.

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