The legacy of Frank Lloyd Wright, America's best-known 20th-century architect, is secure. But 21st-century lifestyles and market forces have combined to put one of his most interesting houses at imminent risk of demolition.

That's what makes the Renwick Gallery's new exhibition, "Light Screens: The Leaded Glass of Frank Lloyd Wright," both fascinating and troubling.

The exhibition, which opened yesterday, celebrates Wright as a glass designer with 44 windows and doors, including a fragile relic from 1897. Abstract geometric designs -- golden sumac, violet wisteria and a "tree of life" -- glow softly with the iridescence Wright loved. Drawings, vintage photographs and two superb models show where "light screens," as he called them, were installed.

How the windows became separated from their houses remains in the shadows, but the issue is pressing today. The market for Wright collectibles is more liquid than the market for the architect's houses. And one rare jewel in suburban Chicago, with 53 original windows, has just been threatened with developer tear-down. It would be the first destruction of a Wright building in 30 years.

Wright (1867-1959) completed nearly 500 buildings, mostly private residences. One in five has been lost to fire or demolition. The exhibition focuses on the years between 1885 and 1923, when he designed 4,365 art-glass windows for his structures.

Wright's glass output rivaled that of a contemporary, the stained-glass artist Louis Comfort Tiffany. But the architect took a new path. He abandoned densely colored and heavy medieval techniques in favor of clear panes with sparkles of gold, delicate color and linear motifs.

Wright's success revolutionized ornamental glass design. That makes the show a perfect fit for a craft museum such as the Renwick. On the other hand, Wright never intended that the light screens be appreciated as artifacts on their own. They were created as part of an ensemble of architecture and interior furnishings. Integration was his "first essential."

At the Renwick, as at four earlier venues of this traveling show, the windows, skylights and glass-fronted bookcase doors must be appreciated against translucent light boxes. Behind them, the shadows of tree branches sway in an artificial breeze. The first time I saw the installation, at its 2001 debut at the American Craft Museum in New York, it seemed innovative. This time, I was struck by its shortcoming: The setting can't convey the passing of the sun or the changing seasons. The windows remain disembodied pieces of some barely imaginable architectural whole.

It's Wright, but it feels wrong.

Many of the light screens came from houses that were torn down before the preservation movement took root. That is the potential fate of the Glasner House in Glencoe, Ill., north of Chicago. The residence was built into a scenic ravine on a one-acre lot a block from Lake Michigan. It is the most endangered of 15 Wright houses listed for sale on the Web site of the Frank Lloyd Wright Conservancy (www.savewright.org).

The owner, Xerxes Bhote, has been seeking a buyer with $1.59 million and a desire to preserve the house and dozens of windows. The only offer has come from a developer who wanted to erect a mansion on the lot. According to Ron Scherubel, executive director of the conservancy, new homes of 10,000 square feet are replacing turn-of-the-century summer "cottages" all over the neighborhood.

Bhote, a 40-year-old options broker, intends to move before the birth of his second child next month. He says the multilevel layout of the 4,300-square-foot house won't suit a family with two toddlers. In a phone conversation this week, he described the situation as "not yet desperate," but he has set a June deadline for sale.

Architectural historians view the house as the first of Wright's site-specific designs, and thus a forerunner of Fallingwater, which cantilevers over a brook in Pennsylvania.

An ideal buyer would live in the house and submit it for landmark designation, but as Scherubel says, the pool of Wright fans able to buy the architect's houses is dwindling. Other endangered residences have been turned into public museums, but the location of this one precludes that. Relocation -- a fate that saved the Pope-Leighey House, which was moved from Falls Church to Woodlawn Plantation in Mount Vernon in the 1960s -- has been proposed. But it would destroy the essential context.

"When it gets to absolutely the last moment and the bulldozers are coming down the street," Scherubel says, relocation would be preferable to demolition. But he likens the result to "putting Fallingwater on a Nebraska farm."

The windows, which are highly marketable, could become a separate issue.

A wall panel in the exhibition, which was curated by glass scholar Julie L. Sloan, indicates that "all were removed in the past and have been lent by private collectors and museums."

One of the most beautiful screens, a full-blown sumac design from the Susan Lawrence Dana House in Springfield, Ill., was a prototype for some of the 250-plus originals at the house, which is now a museum.

But examples also have been removed from the Meyer May House, now a museum in Grand Rapids, Mich., and from the Darwin D. Martin House in Buffalo, which stood vacant for decades. Then-Sen. Daniel Patrick Moynihan stopped a 1993 auction of Martin House windows, securing their return to Buffalo, where restoration is underway. (Forty originals were displayed at the National Building Museum in 2000.)

At a Christie's auction in 1999, a window from Wright's Avery Coonley Playhouse brought $244,500. A decade earlier a playhouse window brought $260,000 at Sotheby's. But Barbara Deisroth, head of 20th-century decorative arts at Sotheby's, says that today she would urge an owner not to remove light screens from their setting.

Bhote has been told that his windows could bring $400,000 to $700,000 at auction. That would not be his choice.

"We look at that as the same thing as tearing down the house," he says.

The Glasner residence is a perfect living example of the "light screen" effect that the Renwick show tries to explain. The architect wrote of "awakening the desire to escape from the prettified cavern of our present domestic life and to see the clear countenance of nature."

At Bhote's house, light reflects off the snow in winter, flooding the walls with white light.

In spring, the combined effect of nature and Wright's amber glass washes surfaces with pale green. In fall, walls take on the hue of autumn leaves.

"It's awesome. It's very subtle. It's fantastic," he says.

When Bhote moves, only 52 originals will convey. The family will take one as a keepsake, just as the previous family took two. He knows it will never have the same effect again.

"There's a huge difference between living it and owning it," he says.

Light Screens: The Leaded Glass of Frank Lloyd Wright runs through July 20 at the Smithsonian American Art Museum's Renwick Gallery, Pennsylvania Avenue at 17th Street NW. 10 a.m.-5:30 p.m. daily. Free. Call 202-633-8998 or visit www.americanart.si.edu

The Renwick show includes Frank Lloyd Wright's "light screen" from Avery Coonley Playhouse in Riverside, Ill.The Meyer May House in Grand Rapids, Mich., now a museum, has Wright windows in their proper setting. At far left, a full-blown sumac design from the Susan Lawrence Dana House in Springfield, Ill., was a prototype for some of the 250-plus originals at the house.For sale: The Glasner House near Chicago retains dozens of original windows.