Salvage Artists.(Single Speed Design)(Big Dig House)

One day in the winter of 2003, John Hong opened an e-mail to Single Speed Design, the architecture firm he runs with his wife, Jinhee Park, in Cambridge, Massachusetts. It was from a structural engineer named Paul Pedini, who said that he had seen a Single Speed project and liked it so much that he wanted to hire the firm for an unusual project. He explained that he worked at a contracting company that had spent a decade on the Big Dig, the huge project to replace Boston's elevated Central Artery with a tunnel, and that he had come up with the idea of using steel and concrete salvaged from the project to put up a building. "It would be sort of like Junkyard Wars meets Habitat for Humanity," he wrote.

Hong wondered how to respond. "You get a lot of weird e-mails if you put your sign in front of a construction site," he said. But he and Park went to meet Pedini in a junk yard a few miles north of Boston where the company was storing highway sections. "When I saw all this stuff, I realized he was serious," Hong said.

The eventual result was the Big Dig House, which was finished early last year. One of the more improbable pieces of serious architecture in the United States, it has won a couple of architectural awards and has brought Single Speed a level of acclaim unusual for such a young firm. The basic structure is entirely made up of salvaged steel and concrete from the Big Dig--three hundred tons' worth. Because the materials were obtained for free, and because Pedini was able to do much of the construction himself, the house, which measures forty-three hundred square feet, was built at the strikingly low cost of approximately a hundred and seventy-five dollars per square foot. Yet it doesn't look like a recycled highway, and it would be among the best contemporary houses in the Boston area even if it had been built the old-fashioned way.

The house sits among a well-known group of modern houses called Six Moon Hill, in Lexington, a suburb northwest of Boston. Other than the concrete foundations, the concrete-block garage wing, and a huge X of steel tubes used for wind bracing, the exterior is mostly glass and cedar siding, softened by an elaborate roof garden atop the garage. The garden is made possible by thick highway slabs of reinforced concrete, capable of supporting three feet of soil. (Not all the systems within the house are green, but the rooftop garden uses recycled rainwater.) Steel beams from roadway tunnels form the basic structure of the house but are mostly invisible until you go inside. The front corner of the facade has a two-story glass window, behind which is a soaring, double-height space topped with steel beams and punctuated by an open steel staircase. It is exhilarating: one part urban loft, one part suburban house, wrapped together into a good-natured tutorial in sustainable building.

Park is thirty-four, and Hong is thirty-eight. In architect-years, this is young, and it's too early to tell whether they will go on to establish significant careers. Nonetheless, in their aspirations and choices, they typify much of what it is to be a young architect in America today. Their Web site is more polished than their office, which occupies a storefront in a small wooden commercial building in Cambridgeport, a rapidly gentrifying neighborhood between Harvard and M.I.T. The name Single Speed comes from the bicycles they ride. "It's Cambridge, all of us ride bikes," Hong said. "We didn't want an overintellectualized name." Hong and Park met at Harvard, in 1997. Park had recently arrived from South Korea, where she had grown up. She is quiet and intense, and uncompromising in her determination to carry through a design to the smallest detail. (For one project, she produced a full-size drawing of the lighting and curtain tracks, convinced that it was the only way to get the contractor to arrange them exactly as she wanted.) Hong, who grew up in Virginia and has a kind of affable swagger, is the more pragmatic of the pair. While working for a couple of years as an intern in a large architectural office in New York, he pursued a ...