Jennifer Siegal feels more than a touch of excitement when she sees a flatbed carrying housing modules. It’s not simply the idea that a home can be built in a factory, delivered to a site, and hoisted into place in hours, but the larger implications of how mobile architecture responds to the way we live today. For Siegal, prefab is “a more intelligent way of inhabiting the landscape.”

Since founding the Office of Mobile Design (OMD) in 1998, the designer has been exploring the possibilities of offsite construction, repurposing materials, and portability. Siegal doesn’t exactly see herself as an evangelist, but she’ll quickly tick off the reasons prefab makes sense in an urban context now more than ever. There’s the housing crisis, for one, but prefab also costs 10 to 15 percent less than conventional building methods do, can shave construction times in half, and utilizes more sustainable building practices.

Siegal’s own home in Venice, which she shares with her daughter, Sydney, has served as a laboratory for these ideas since 2002. Gutting the existing bungalow on the 4,900-square-foot lot, she expanded the structure by installing a 200-square-foot truck trailer alongside it. A freestanding, two-story studio for her firm followed several years later (“Method Lab,” Dwell, November 2007).

The latest addition reflects her preoccupation with a new model of urban density, one she calls “vertical urban infill.” A stack of three factory-built modules have replaced the truck trailer and added a little more than 1,000 square feet to the house, bringing it to a total of 2,200. By situating the addition behind the bungalow, Siegal minimized the impact at street level. “It’s not disruptive to the neighborhood,” she says. The process was also remarkably efficient: After a 21-day build-out in the factory, the modules were installed by crane in just three hours; finishes took another three months.

Faster turnaround time and less material waste are only part of the equation. For Siegal, portable structures also make sense in a society that’s increasingly on the move. That’s something she understands from experience. She grew up in New Hampshire, spending part of her high school years in Israel and traveling to the Sinai and Bedouin villages. After college, she packed up and headed west to California, stopping along the way for a six-month sojourn at Arcosanti, Paolo Soleri’s utopian community in the Arizona desert.

Fresh from earning her master’s in architecture at SCI-Arc in Los Angeles, she worked for architects Craig Hodgetts and Ming Fung. After receiving a grant to rethink modular classrooms, she began to apply her findings to housing. “I just had to change the program—add a little more glass and ventilation,” she recalls.

Light and ventilation were very much on her mind in her own home. There’s a feeling of airiness as the volume expands from the original bungalow to the addition, reinforced by the California-sourced white oak floors that unify the spaces and the translucent polycarbonate panels that wrap the stair tower to the master bedroom and rooftop deck.

The diagrid structure of the steel modules themselves is another passion of Siegal’s. “It allows for a more open interior volume and doesn’t rely as much on internal structural steel,” she says.

Throughout the house are materials and pieces that Siegal has been gathering and repurposing over the years. The doors that open to the back garden were salvaged from a grocery store in East Los Angeles, and a Kirei wall board was upcycled from OMD’s ShowHouse prefab model. Paintings by her father, abstract artist Sidney Siegal, share space with furnishings from her former homes in the California desert; in Marfa, Texas; and in downtown Los Angeles.

As with her other projects, Siegal sees her house as an opportunity for collaboration—not just with Silver Creek Industries, which manufactured the modules, but with colleagues, friends, and students. Designer Mimi Shin, a neighbor, consulted on the interiors, and OMD interns Nicole Blue and Gabriela Schweizer—undergraduates at the University of Southern California, where Siegal is an adjunct associate professor in the School of Architecture—helped craft the rope-and-leather wrapping on the stair rail. “Even if the structure is fabricated off-site, I want the local community involved,” she says.

Housing the master bedroom and bathroom, the second-floor module features a skylight and operable windows oriented for year-round passive cooling. Vintage Paul McCobb pieces join a bench from Target and sliding doors made from wood salvaged in the renovation.

The artificial turf that lines the 360-square-foot rooftop deck was destined for a dumpster at the Santa Monica Airport when Siegal intervened: “I asked what they were doing with the scraps, and they said, ‘After five o’clock, we just close our eyes,’” Siegal says. “I came back with my contractor, and now those scraps have a new home.”

In the front yard, Siegal has created an equally cool—and mobile—place where her daughter can hang out with friends. Made from a unit load device that transports airline cargo, the simple box structure is a prototype for the designer’s new prefab playhouse.

Siegal, who was awarded the 2016 arcVision Prize–Women and Architecture last spring, says she hopes that combining factory-built modular systems with existing buildings is an approach that will encourage city dwellers to add on rather than tear down. “You don’t need to erase the past to create the future,” she says.

“The Eameses talked about good design for the masses,” adds Siegal, “and we’re at that moment where people are accessing good design at a rate they never did before. The flood of new creativity doesn’t eclipse the designer; it makes you appreciate even more what good design is.”