Keren Milchberg Porat sees herself and her family as the best guinea pigs to test design ideas. “How we live is research for what I do,” says the founder of Tel Aviv, Israel, architecture and design firm Studio ID253. “And I believe in exploring the mind-set of living differently—not in the way our brains expect.”

Five years ago, Keren’s notion of a comfortable home was pushed to its limit by a three-week business trip with her family to notoriously space-challenged Tokyo, Japan. At the time, she’d been living with her husband and business partner, Shai Porat, pregnant with their son, Mai, in a roomy 1,100-square-foot loft; their temporary quarters in Tokyo turned out to be a closet-like studio. Despite Keren’s initial qualms, she found herself thoroughly inspired by the experience. “Everything in the Japan apartment was so well thought out,” she says. “It felt very good—and a seed was planted in my mind.”

Upon their return to Tel Aviv, that seed took root when the Porats discovered a dilapidated Land Yacht Sovereign International 31-foot Airstream trailer parked in a Tel Aviv suburb. Keren had lived in the USA as a student and revered the iconic brand, but she’d never heard of an Airstream existing in Israel. The Porats eventually tracked down the owner—who had bought it from a Bulgarian diplomat who’d likely imported it from the USA back in the ’60s. Much to the Porats’ delight, he was willing to sell. They decided the trailer would make for an ideal experiment in microspatial low-cost living—a way “to have, like, a mental trip,” says Keren.

The couple revamped the interior themselves, taking care to preserve as many original elements as possible, including the existing lighting and windows: “The design was already very clever,” Keren says. They stripped and repainted the cabinetry, tore out the disintegrating floor, installed oak parquet floors, replaced the mechanical systems and appliances, and painted the walls white.

Not wanting to live, literally, on the street, the couple searched for land with utility hookups to rent; they found an idyllic plot, nestled within a vast fruit orchard, in a suburb near Tel-Aviv, ten minutes north of the city and just off the beach. The plan was to stay for three months. Instead, they decided to make it their permanent home. “We didn’t feel like living in a trailer was hard or small or stressful,” says Keren. “We felt the opposite.”

Still, with plans to expand their young family, the Porats thought that an Airstream alone wouldn’t suffice. In conceiving an addition, Keren decided against cutting a larger opening into the curved wall—a popular move by Airstream revivalists. Instead, they left the body intact and erected a separate playroom—a daytime domain for the children.

The vitrine-like structure shares a continuous pine-plank floor with a deck and opens up with a wall of sliding glass doors, creating a cohesive indoor-outdoor room at the trailer’s front doorstep. Galvanized steel cladding echoes the Airstream’s exterior, furthering the sense of continuity. Built by Shai, the playroom is made almost entirely of salvaged material, down to the found-wood studs. From the petite scale to the asymmetrically installed, kid-height custom windows, it’s designed to “intrigue the interest, and enhance observational skills and visual and mathematical thinking” of the couple’s two children, five-year-old Mai, and Naiya, who will be two in April.

Lest such a setup still seem too cramped for a family of four, Keren points out that the womb-like trailer, where the family sleeps, is actually quite kid-friendly: “The size and lack of corners make them feel very safe and secure,” she says. As for the grown-up Porats, foregoing extraneous possessions, decor, and square footage has had its own benefits. “We feel free in our minds here, very open,” Keren says. “Living this way is like a meditation.”