Two concurrent exhibitions approach the deceptively humble architectural feature of the window from utterly different angles. At the Renwick Gallery, "Light Screens: The Leaded Glass of Frank Lloyd Wright" is, unsurprisingly, the prettier of the two shows, highlighting as it does the iconic architect's nature-based and geometric leaded-glass patterns and how he integrated them into his pioneering buildings. The National Building Museum's "Picture This: Windows on the American Home," on the other hand, has a stealthier agenda.

Even as "Picture This" addresses historical changes in American window styles and technological innovations, it raises some sneaky, even troubling questions about what exhibition historian Sandy Isenstadt calls "mediated looking" (an idea one might reasonably expect to encounter in a contemporary art museum, but not necessarily in one dedicated to the building arts).

Frankly, I found the notion far more interesting to chew on than the predominantly aesthetic concerns of the Renwick's lovely but far less theoretical show.

At first blush, "Picture This" hits you like a bit of an advertisement for Andersen Corp., the window manufacturer that, in honor of its 100th birthday, is exclusively sponsoring the exhibition. Although its displays incorporate windows by such competitors as Marvin and Pella, the lion's share of space is given over to such Andersen products as the double-hung Pressure Seal window of the 1950s, the prefab Windowalls and Flexivent awning windows of the 1960s and the company's latest version of its Perma-Shield vinyl-clad technology.

I realize that someone has to pay for things like this, but the thinly disguised commercial doesn't go down well.

However -- and this is a big however -- by the time I had reached the end of the exhibition I had encountered some far juicier ideas. This is chiefly as a result of Andersen's "Odyssey Project," a prototype computer-screen-cum-window, and the proposed Access House, a glass-walled beach home designed by architect Joel Sanders that incorporates television, video, Internet and security-cam programming into something called the E-core, a kind of central electronic spine that runs up through the house like a high-tech chimney.

Mind you, I despise both these ideas. The Odyssey Project's notion that you might take a window, whose very reason for being involves transparency, and then obstruct its view with a flat-screen monitor -- just so you can have access to the Web or a DVD player while standing at the sink doing dishes -- seems perverse. And the ironically named Access House's Big Brother-like surveillance system, a technological "innovation" only necessitated by the paranoia resulting from the fact that the entire house is a space-age fishbowl, undermines the very motivation people used to build beach houses in the first place: that is, for sun, ocean breezes and, believe it or not, relaxation, not crouching in your state-of-the-art bedroom while you wonder whether someone is spying on you or trying to break in.

This hits close to the paradox that is central to both these shows -- although, frankly, one might have to look harder for it at the Renwick. Because of its translucency, the window is the only feature of a house that is simultaneously inside and outside, both portal and barrier. It must provide light along with affording privacy. It must let in the air, but keep out the weather and pests. We want more of them in our houses, but not so many that we feel naked.

In a sense, the idea of the window frames some of the contradictions of our society. We are, as Isenstadt notes, both predator -- for better views of an "aestheticized" outdoors -- and prey -- of criminals and Peeping Toms. Our fabled openness exists only in tension with our deeply ingrained love of privacy (not to mention our fear of the Other).

In a sense, it's all summed up by one final display in "Picture This." It's a window that has been coated with the perforated film that is sometimes laminated over bus windows, enabling passengers to see out but allowing advertisers to print their messages and images on the outside. A kind of two-way screen that allows a clear view one way but restricts vision in the other, it encapsulates some of the show's themes of the watcher and the watched.

If you look hard enough, you can even see these contradictions in the leaded-glass windows of Wright. Even his name for them, "light screens," suggests the duality of aperture and closure, access and barricade, the freedom of nature and the illusion that we can control it with technology.

In other words, we pay for the views we seek in more ways than one -- financially, to be sure, but also with a little piece of our soul.

PICTURE THIS: WINDOWS ON THE AMERICAN HOME -- Through Aug. 11 at the National Building Museum, 401 F St. NW (Metro: Judiciary Square). 202-272-2448. www.nbm.org. Open Monday-Saturday 10 to 5, Sundays 11 to 5. Free.

LIGHT SCREENS: THE LEADED GLASS OF FRANK LLOYD WRIGHT -- Through July 20 at the Renwick Gallery of the Smithsonian American Art Museum, 17th Street and Pennsylvania Avenue NW (Metro: Farragut West). 202-357-2700 (TDD: 202-357-1729). americanart.si.edu. Open daily 10 to 5:30. Free.

Public programs associated with the Wright exhibition include:

Sunday at 1 -- Exhibition tour; repeated Sundays through the exhibition closing (except April 20).

Sunday at 2 -- Slide lecture with Craig Tuminaro, curator of Wright's Pope-Leighey House.

Wednesday and May 7, June 4 and July 2 at 1 -- Film screening: "Frank Lloyd Wright: The Masterpieces."

April 16, June 11 and July 9 at 1 -- Film screening: "Frank Lloyd Wright: A Film by Ken Burns and Lynn Novick."

April 23, May 21, June 18 and July 16 at 1 -- Film screening: "Frank Lloyd Wright: The Mike Wallace Interviews."

April 30, May 28 and June 25 at 1 -- Film screening: "Three Wright Eras."

May 18 at 2; June 5 and 26 at 7 -- Staged reading of "Work Song," a new play by Eric Simonson and Jeffrey Hatcher exploring Wright's life and career. For reservations, call 202-547-1122 and press 4.

June 14 at 1 -- The Peabody Ragtime Ensemble plays music from Wright's era, followed by a workshop in which children design their own light screens using craft material.

June 27 at 7 -- Eric Lloyd Wright, grandson of the famous architect, talks about Wright's legacy and architectural trends of today and tomorrow. $40. Registration required. Call 202-357-3030 or visit www.residentassociate.org.

June 28 at 1 -- Slide lecture with exhibition curator Julie Sloan.

July 20 at 1 -- Glass artist Jimmy Powers talks about how to create, restore and install stained- and leaded-glass windows.

The leaded-glass windows of the Frank Lloyd Wright-designed Meyer May House in Grand Rapids, Mich.Mrs. Harold Garrity looks out onto the world in 1942.Windows provide both protection from and appreciation of nature.