The idea of a well-oiled assembly line churning out gleaming and affordable new houses, flooded with light and as compact as a ship's cabin, is a well-worn Modernist fable.

For the average middle-class American, however, prefabricated housing has always lacked sex appeal. The masses tended to prefer a traditional style, no matter how shabbily designed, and never really bought into it. Nor did most of the industrialist tycoons with the money to make the dream real.

So ''Home Delivery: Fabricating the Modern Dwelling,'' which opened on Sunday at the Museum of Modern Art, is a delightful surprise.

Organized by Barry Bergdoll, MoMA's chief curator of architecture and design, it presents more than 80 projects, from humble experiments in suburban living to stunning works of creative imagination. In a tour de force Bergdoll was able to build five full-scale model houses for the show in a lot just west of the museum. The effect is startling: expressions of a suburban utopian world surrounded by Midtown's looming skyscrapers.

But like all great exhibitions, ''Home Delivery'' is not simply a crowd pleaser. It's the kind of loving, scholarly achievement that is rare in today's architectural climate, which so often favors cheap spectacle over probing intellect. Bergdoll makes a convincing case that prefabricated housing was both a central theme of Modernist history and a dream that remains very much alive today.

To experience the show at full throttle, start with the main exhibition in the museum's sixth-floor galleries. It opens with a vision from the mass-produced utopia of tomorrow: two gorgeous wall fragments - one by Ali Rahim and Hina Jamelle, the other by Jesse Reiser and Nanako Umemoto - that push the limits of customized computer technologies. Their voluptuous surfaces suggest a hybrid of industrial materials and free-form organic design.

Just above to the right is a projection of a 1920 Buster Keaton film in which fumbling young newlyweds try to assemble a prefabricated house. Dropped off the back of a truck, the house's various parts were mislabeled by the woman's jilted former suitor. The result, once it is assembled, is a chaotic jumble of tilting walls, irregular windows and doors that open to nowhere.

The film pokes fun at those who spend their lives chasing fantasies. But it also hints at the instability at the core of any creative venture, teasing out one of the exhibition's most haunting themes: the conflict inherent in the so-called American dream. In many ways the prefab house embodies the tension between a desire for stability and a quixotic faith in social mobility.

The history of prefabricated dwellings is one of false starts and foiled dreams. In 1833 a London carpenter identified as H. Manning created one of the first, the Manning Portable Cottage, for his son, who was sailing off to make his fortune in Australia. Made of precut wood posts and panels, the house could be conveniently packed in a ship's hold and reassembled. A single man could carry most of its lightweight components. (The house became a mild commercial success.)

Like Henry Ford's cars, such houses were intended to be mass-produced objects, affordable machines for both the rising middle class and the working masses. In Le Corbusier's famous words they were ''machines for living.'' But at their most idealistic, they also sought to express the freedom of a society constantly on the move.

They were in a sense an effort to tear the house up from its foundations, to make it as mobile as the individuals these buildings were meant to serve.

That notion reaches full force in the decade immediately after World War II, when most architects believed that military industrial production would be retooled for the construction of a more egalitarian, peacetime society. That vision is underlined in the show by the rickety steel frame of Jean Prouvé's Maison pour l'Institutrice, a reworking of his 1948 Maison Tropicale, a masterpiece of prefabricated design that was conceived as a kit of standardized parts that could be transported by air to the French colonies and assembled on site. The lightweight frame of its vented roof, which has the airiness of airplane wings, sums up the aspirations of a generation of architects.

Just beyond it stands a full-scale version of the Lustron House, a suburban home that began production the same year. If the Maison Tropicale reflects a wholehearted embrace of the new, the Lustron House is its counterpoint: modern technology draped in nostalgia. A steel structure manufactured to look like a conventional suburban wood-frame house, it embodies the fear of the unknown that has historically pushed the most creative architecture to the periphery of the profession.

As we all know, the traditionalists won. And from here the show takes a noticeable turn into fantasy, as if the architects grew to accept the limits of their dream. The most playful example is Archigram's 1965 Living Pod, an amoeba-shaped capsule with mechanical systems plugged into the side. Supported on squat mechanical legs like an Apollo landing craft, the pod had inflatable floors and furniture so that it could be packed up and moved easily.

Yet the work that best embodies the show's spirit is Kieran Timberlake Associates' four-story Cellophane House. Supported on a lightweight steel frame that is bolted together so that it can be taken apart easily, it is as simple to assemble as a child's Erector Set. Photovoltaic cells are integrated into the structure's transparent cellophane skin, their copper filaments tracing a delicate pattern across the facade. The skin gives the house an ethereal, temporary quality, and it stands so gently on its site that it seems afraid of doing harm to its surroundings.

Environmentally sensitive and devoid of cynicism, it's a perfect end to the show. Hope rises again, more cautious and subdued - a sign that we're finally learning to navigate the line between heroism and hubris.

Copyright 2008 International Herald Tribune