One of the first things you notice about the Japanese architect and architectural historian Terunobu Fujimori is his voracious appetite. His particular brand of hunger extends not only to food—which he devours swiftly and animatedly, crumbs flying Cookie Monster–style—but also to an ardent intellectual curiosity about the world, especially as it relates to architecture, his all-consuming passion for more than 30 years. A longtime professor at the Institute of Industrial Science at the University of Tokyo, Fujimori came to designing late—he got his first commission at age 44, 19 years ago—but he has since conceived some of Japan’s most startlingly original buildings, on average one per year.

Leading the way to his office at the university (he calls it his “laboratory”), he walks swiftly and steadily, as if propelled on a Segway, his salt-and-pepper hair waving behind him. We sit at a table sipping green tea, and Fujimori thumbs through his sketchbook, discussing the atypical genesis of his career while gobbling tea cookies and sketching almost continuously with a blue pencil. Fujimori grew up in a tiny, rural village two hours south of Nagano, where he helped care for the surrounding forests, as the local villagers have done for more than 400 years. He studied architectural design in college but quickly became disillusioned by the lack of hands-on technical training—he was more interested in building than in design, he realizes now—and moved to Tokyo to pursue a PhD, spending the next 20 years as a scholar and professor of modern Japanese architectural history.

Fujimori basically fell into designing buildings after his native village commissioned him to design a small history museum for a local family with ancient ties to the area. As he pondered what form the building should take, he felt the weight of all of architectural history bearing down on him. “Since I was a famous architectural historian,” he says, “I thought my architecture should be totally unique, dissimilar to any architecture that came before. I figured that if I did something traditionally European or Japanese, everyone would say ‘Oh, it’s because he’s a historian.’ I didn’t want that criticism.” But at the same time, he wanted to stay away from anything too contemporary. “Some of my closest friends, like Tadao Ando and Toyo Ito, were architects who were starting to get famous, and I didn’t want them to laugh at me and say, ‘Oh, you mimic my work.’”

His peers found the building intriguing. “Terunobu Fujimori has thrown a punch of a kind no one has ever seen before at ‘modernism,’” wrote the architect Kengo Kuma. Encouraged, Fujimori decided to continue designing. With no other clients in sight, he built a house for his family in a Tokyo suburb. Inspired by the plant-covered thatched roofs prevalent in Normandy, the Tanpopo (Dandelion) House has strips of volcanic rock affixed to the facade, with flowers and grass blooming in the grooves between them. The thick walls mean that the house is extremely well insulated and energy-efficient, a by-product of the design rather than a direct goal. While Fujimori admits that his buildings tend to be ecologically sensitive and extremely energy-efficient, he is wary of the contemporary conception of green design. “As an architect, I deal with the visual effects. Energy conservation is an engineer’s work. My intention is to visibly and harmoniously connect two worlds—the built world that mankind creates with the nature God created.”

Earlier that day we’d met in Kiyosumi, a town 60 miles north of Tokyo, to visit his most recent project: a 1,080-square-foot concept house he designed for the Tokyo Gas Company Ltd., Japan’s largest natural gas provider. Coal House, as Fujimori calls it, uses exclusively gas-powered appliances and is full of quirky details: Squat, hobbit-scaled doors conceal a bathroom and side entrance (you literally need to duck to enter); the children’s room is accessible only by a steep ladder (“It’s okay,” Fujimori reassures me when I inquire about late-night bathroom runs, “children are like monkeys”); and a tiny tearoom hangs off the second story like a jutting upper lip, echoing the silhouette of his earlier Charred Cedar House from 2007. Both projects are extraordinarily striking, thanks in large part to their exterior siding, charred cedar boards with a crackled, crocodile-like texture—an ancient Japanese technique that seals the wood against rain and rot but is seldom used by contemporary architects. This is in part because it’s labor-intensive—it takes seven minutes to char three boards—and also because the method is considered primitive. “No educated architect would use this material,” says Fujimori with pride, grinning broadly. The effect certainly makes an impression; as we chat in front of the Coal House, a neighbor walks by slowly, swiveling her head, her mouth visibly agape.

Little about the way Fujimori works is conventional. He doesn’t have a firm per se but rather recruits promising graduate students to help him flesh out the details of each project after he’s done all the drawing. He makes his architectural models by hacking tree stumps into abstract, sculptural shapes using a chainsaw. Galleries abroad have offered to buy them, but he refuses. And when he’s completed the final drawings for a project, he invites his clients to his weekend house in Nagano for a little ceremony he’s devised. Sitting in his private Too-High Tea House, perched 20 feet in the air and wavering on two forked tree trunks, he hands them a hand-rendered version of the final plans. “If they don’t like my design, I shake the building!” he says, laughing heartily.

Fujimori hires professionals to do all the structural and electrical work on his buildings but handles many of the interior finish details himself, with a motley group of volunteers that he calls the Jomon Company—so named for the Neolithic period of Japanese history and for the primitive tools they use to give Fujimori’s interiors a warm, roughed-up feel. When the structure is nearly complete, this loose collective of close friends—a painter, a novelist, a book publisher, a sake brewer, a priest—gather to do whatever unusual task Fujimori has set aside for them: planting hundreds of leeks in individual pots atop a gabled roof; weaving a bamboo screen for a copper-plated pottery studio; or cutting irregular chunks of wood with stone-carving tools and embedding them in a tea house’s vaulted ceiling. “Instead of playing golf that weekend, they work,” says Fujimori, hastening to add, “I never pay them. If you pay, it’s labor!”

Fujimori clearly relishes his iconoclast role, even as he receives increasing recognition and respect as a designer: At the 2006 Venice Biennale he exhibited his unconventional architectural models, and in 2007 the Japanese publishing company Toto released a monograph of his work. But increasing fame and more prestigious commissions don’t mean he’ll change his unconventional working methods anytime soon. He’s spent the past several years roaming the globe for new ideas, applying his historian’s mind to collect inspiration from ancient models: mud architecture in Mali, adobe buildings in the American West, and the famous Caves of Lascaux in southwest France. These spare, stripped-down structures remind us that we all share primal instincts that can be aroused and satisfied through design: for shelter, warmth, and community. Fujimori may dismiss sustainability as a side note in his buildings, but his modern interpretation of the Neolithic captures a truth too often lost in our scramble for eco-credibility: Working with nature is sometimes the most radically green approach an architect can take.