Small Home: Circularity Cabin

Designing a house on a site that might lose half of its land due to future road widening sounds challenging to say the least. How did this influence your response?

The clearly defined timeline, in which the building must be dismantled before reaching its physical lifespan, allowed us to set ‘how the building should end’ as the starting point of the design. We have long been exploring circularity, but this constraint turned what we had previously considered as theoretical ideas into extremely concrete and pressing challenges. In other words, this constraint served as a powerful catalyst, allowing us to translate our underlying values of circularity into concrete design methods and, in turn, enabling the creation of a feasible and realised prototype.

I understand that the structural components use DIY-standard timber that can be purchased at a hardware store. What was your motivation here?

At the time of construction, rising timber prices due to the lumber shortage were a major problem. Working with a limited budget, we reconsidered how to process and source timber, and came up with the idea of constructing the building entirely from small, easy-to-handle standard components that can also be purchased at hardware stores. As a result, I devised a “Semi-Property” that can be easily constructed, dismantled, and relocated – a home that moves with its occupants. This was made possible by assembling the main framework using only bolts and screws without pre-cutting standard lumber. Even if it is not relocated, the timber can be easily stored and reused, achieving a truly circular approach to the home’s architecture.

As a small house under 60 sqm (646 sqft), we also paid attention to making it easy to maintain by exposing its structure, so that the occupants can carry out repairs themselves. They can go to a hardware store and handle most fixes on their own. In this way, the design enables longer use, reuse and repair within the circular economy, while also aligning with a design philosophy of ‘restoring rights to residents.’

Did working with DIY-standard timber present any challenges?

We had to ensure the necessary structural strength while realising a lightweight, two-storey timber post-and-beam house that does not rely on precut components. In particular, it was necessary to devise a method to secure the horizontal stiffness of the floor without using plywood. In the end, we fixed two screws at each intersection of the beams to prevent rotation and ensure the floor’s horizontal rigidity.

Despite all of its structure being on show, Circularity Cabin has a quiet elegance about it.. Where did you draw the design inspiration from?

The basic grid of the house is based on the ‘silver ratio’, a traditional Japanese proportion. In Japan, carpenters have long regarded the silver ratio as a ‘mystical proportion,’ and it has been incorporated into many architectural structures, including the Kondō of Hōryū-ji, and Ise Jingu. It is not simply a standard of beauty; it is also grounded in uniquely Japanese rationality and the concept of mottainai. Circularity Cabin was designed with this concept in mind. Specifically, the structural spans are set on a 1820 mm pitch. Most Japanese building materials are developed around this 1820 mm module, which can easily be divided into 910 mm, 606 mm, 455 mm and so on. This modular system is deeply integrated into Japanese architecture and manufacturing, minimising material waste.

We were also mindful of restoring a connection with nature, which is often lost in urban living. For example, the clerestory windows, angled in various directions, are one way we achieved this.

Can you tell us more about the clerestory windows?

On the side of the house facing the main road, which experiences heavy traffic and is the southwest-facing side with the highest heat load, we decided not to include any openings. Instead, we installed three clerestory windows. This allows the house to bring in abundant light and ventilation while maintaining privacy.

Circularity Cabin is situated in a unique yato, a valley surrounded by mountains, and its proximity to the sea further creates distinctive wind conditions. Specifically, due to the difference in specific heat between land and sea, sea-land breezes occur, causing the wind direction to change between day and night. From morning to early afternoon, the breeze comes from the northeast, and from evening to midnight, from the southwest. The orientation of the clerestory windows was optimised through environmental simulation to make the most of these breezes.

These same clerestory windows also bring in light that changes with the seasons and time of day, allowing the occupants to experience these natural rhythms. At night, the moon is visible through the clerestory windows too. Through these design strategies, the occupants can engage with the rhythms of nature while living in an urban environment, using the architecture itself as a medium for that connection.

Is the floor on the second floor also related to these design strategies?

Yes, the second floor is designed as a fully slatted floor, allowing light and breezes from the clerestory windows to reach the first floor. This creates a soft, even light while avoiding glare and heat from direct sunlight. It also removes the constraint that windows must belong to a specific floor: by positioning the windows midway between the first and second floors, they contribute to the environment on both levels.

As the phrase “restoring rights to residents” suggests, I love the idea that the occupants can become participants in shaping their environment, rather than just passive residents.

In most buildings, not just houses, the environment that users can actually influence is usually limited to opening or closing curtains, switching the air-conditioning on or off, and similar actions.

In Circularity Cabin, the occupants can treat the furniture on the slatted floor of the second level as flexible elements of the environment, controlling the microclimate much like changing clothes according to the seasons. In practice, the occupants rearrange the furniture according to seasonal changes in light, which allows them to better feel the cool airflow from the second-floor air-conditioner. Thanks to these adjustments, they are able to live very comfortably, relying on just one air-conditioner in summer and only underfloor heating in winter.

What do you feel Circularity Cabin has achieved and demonstrates as a prototype of a house for the future?

We are proud to have made it possible for occupants to understand, maintain and adjust their environment by themselves, without relying on experts. We believe that this project has redefined the relationship between architecture and its users.

This project does not end with completion. We were able to establish a new relationship between architects and occupants, in which the furniture arrangement is continuously monitored and the architect provides advice to maintain a comfortable environment and way of living. In addition, although the timing of the road widening is uncertain, flexibility has been secured in case of relocation or reconstruction. The arrangement of the clerestory windows can also be adjusted and optimised according to the terrain and wind conditions of a new site.

In this way, Circularity Cabin has been realised not merely as an abstract concept of circular architecture, but as a concrete, tangible building. I also believe that there is value in the process itself, which transformed various constraints into opportunities. We consider the most important outcome of this project to be the fact that it actually combines comfort and sustainability in the daily lives of its occupants.

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