Kumagaya, located about 40 miles northwest of Tokyo, is known as one of Japan’s warmest cities, and in the summertime it’s not uncommon for its temperature to surpass 100 degrees. So when architect Hiroo Okubo and his firm Chop + Archi were commissioned by a young couple to design a home there, he knew that encouraging airflow would be a top priority.

The site is also situated next to train tracks, so it was important to provide privacy. And since the couple anticipated starting a family, he wanted to give them a variety of distinct spaces, despite the home’s modest square footage.

According to the architect, the couple shared many dreams for the home: “‘We may have a growing family in the future,’ ‘We would like to have a café and flea market for the community,’ and ‘We would like to blend in with the community as we live for many years in the town where we both come from,’” he says.

Okubo excels at envisioning homes for confined sites that emphasize privacy and natural light. On a narrow, triangular lot in Tokyo’s dense Setagaya ward, his firm designed a home with few exterior windows—and three voids carved into the corners that form tiny, courtyard-like outdoor spaces.

The architect, who studied furniture and product design before turning to buildings, and whose portfolio includes numerous retail projects and custom furnishings in addition to houses, excels at designing within constraints. “What interests me about furniture and product design is creating tools that people touch and use with their hands,” he says. “In the same way, I try to design for comfort and incorporate experimental elements in architectural design.”

For the 1,160-square-foot Kumagaya House, completed in 2023, Okubo envisioned four quadrants separated by what he calls a “cruciform void.” The layout resembles a traditional ta-no-ji floor plan, which echoes the way rice fields are divided into squares divided by intersecting lines.

But unlike a traditional ta-no-ji configuration, in which the spaces often overlap, the void creates a buffer between the four quadrants of the home. At the same time, it interlinks the spaces and connects them to the outdoors.

“The effective placement of voids in the interior of a house, and the elements that emerge from them, is one of the compositions that we are always considering,” says Okubo. “The cross-shaped void was inspired by the traditional Japanese children’s game of origami.”

The configuration also serves a social purpose: it enables the small family to find little moments of privacy in the compact home. “By placing the cross in the center of the house, four spaces can be created,” the architect explains. “The four spaces are buffered, like an air cushion or bubble wrap, in a relationship that does not bring them too close together.”

The cuboid, three-story home is clad with three different materials: a concrete basement gives way to a cedar-clad main floor and a white stucco upper story. There are no windows on the east facade, so as to maintain privacy from passing trains.

The entry opens to a short hallway that terminates in a terrace. To the left, a set of sliding glass doors open to the double-height living room and kitchen, which comprise one half of the ground floor. In this room, the angled roof soars upward as the white drywall gives way to a ceiling clad in structural plywood. To the right of the entry, there is a lavatory, a stairway, and a separate dining room, which opens to the patio, and the kitchen, via glass doors.

On the upper level, a pair of bedrooms are sectioned off by the central stairway, and an open-air passageway. Just across from each bedroom, sliding doors open to two interior balconies above the kitchen/living area. The home’s roofline is particularly distinctive and origami-like, as each of the four corners rises to an asymmetrical pyramid, yet the points are separated by the central void.

To mitigate Kumagaya’s substantial summertime heat, the house is designed to encourage the stacked ventilation effect. “The cross-shaped voids create airflow,” Okubo says, “while the vertical voids push the hot air upward and allow it to escape through the windows.”

“I try to capture the form as a single ‘mass’ as much as possible, and consider how to use the space created by ‘missing’ certain parts of it,” he continues. “It is interesting to create a space that is indeterminate in its use, and to enjoy the spontaneous phenomena that arise from this.”

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Project Credits:

Architect of Record: Chop + Archi

Builder: Furogori Home

Structural Engineer: Shin Yokoo, OUVI

Civil Engineer: Toshiharu Fukunaga, Kankyo Partners